Complex perovskite-like materials which include magnetic transition elements have relevance due to
the technological perspectives in the spintronics industry. In this work, we report the studies of the electronic
and magnetic characterizations of Sr2CrWO6 and Sr2FeReO6 as spintronics materials at room temperature by
using the linearized muffin-tin orbitals (LMTO) method through the atomic-sphere approximation (ASA) within
the local spin density approximation (LSDA). The interchange-correlation potential was included through the
LSDA+U technique. The band structure results at room-temperature predict half-metallic ferrimagnetic ground
state for Sr2CrWO6 and Sr2FeReO6 with total magnetic moment of 1.878 μB and 3.184 μB per formula unit,
respectively, agreement with the previous theoretical and experimental results.
Using the two forms of Fish-Bone potential (I and II), a self-consistent calculations are carried out to perform the analysis of binding energies, root mean square radii and form factors using different configuration symmetries of 20Ne nucleus. A computer simulation search program has been introduced to solve this problem. The Hilbert space was restricted to three and four dimensional variational function space spanned by single spherical harmonic oscillator orbits. A comparison using Td and D3h configuration symmetries are carried out.
CONTENTS
INTRODUCTION
CONCEPTS OF WALSH DIAGRAM
APPLICATION IN TRIATOMIC MOLECULES
[IN AH₂ TYPE OF MOLECULES(BeH₂,BH₂,H₂O)]
INTRODUCTION
Arthur Donald Walsh FRS The introducer of walsh diagram (8 August 1916-23 April 1977) was a British chemist, professor of chemistry at the University of Dundee . He was elected FRS in 1964. He was educated at Loughborough Grammar School.
Walsh diagrams were first introduced in a series of ten papers in one issue of the Journal of the Chemical Society . Here, he aimed to rationalize the shapes adopted by polyatomic molecules in the ground state as well as in excited states, by applying theoretical contributions made by Mulliken .
Oxygen Vacancy Conduction in Double PerovskitesMegha Patel
Fuel cells and solar panels provide more environmentally friendly alternatives to burning fossil fuels. Fuel cells currently need better oxygen vacancy conducting cathode materials while solar materials need ways of tuning the band gap. Understanding of oxygen vacancy structure and conduction in perovskites and double perovskites is critical in solving these two challenges. A neutron pair distribution analysis study of the double perovskite Sr2MSbO5.5 (M=Ca, Sr, Ba) found that multiple structures where oxygen vacancies significantly altered the local geometry of the system could explain the same neutron scattering measurements. Our goal is to find all the energetically favored structures in these systems and their impact to oxygen vacancy conduction in these double perovskites. Density functional theory (DFT) with the PBE functional and a generalized gradient approximation (GGA) implementation in the Vienna ab-initio simulation package (VASP) was used to find energies. The conjugate gradient method was used to find minimum energy configurations of the Sr2MSbO6 double perovskites from all 23 possible Glazer octahedral distortions. Oxygen vacancies were introduced without distortions, with trigonal bipyramidal distortions, and with pentagonal distortions. All structures were optimized. The minima featured distorted SbO5 square pyramids and trigonal bipyramids in most systems and sometimes MO7-x pentagonal bipyramidal structures with that structure becoming more favored with increasing ionic size for the M ion. Both of these distortions were suggested by experiment to lead to the neutron scattering measurements. A detailed energetic analysis of these options is presented. Further, implications of these distortions on oxygen vacancy conduction in double perovskite systems are discussed.
SURFACE POLARITONS IN GAAS/ALGAAS/LH HETROJUNCTION STRUCTURE IN A HIGH MAGNET...ijrap
The surface polaritons (SP) variation in Ga As/ Al Ga As/ LH hetrojunction composition in the presence of
a strong transverse quantized magnetic field is estimated using the quantum Hall effect case. The
dispersion characteristics of the SPs are investigated using the dielectric constants values of the Ga As and
the Alx Ga 1-x As media and the defined thickness, the Alx Ga 1-x As medium. The dispersion behaviours
calculated results are listed for considered cases. It was shown that the frequency values against the wave
vector values are affected in a strong manner by changing thickness, of the Alx
Ga 1-x- As media and by
changing the variation of the dielectric constants of Ga As against the Alx Ga 1-x As. The significance
effects of the use of the left-handed (LH) medium as an upper layer of the proposed composition was
demonstrated; the frequency values are remarkably increased using LH material as an upper layer. It was
noticed that at certain conditions of the LH upper layer composition, similar results have been obtained
such as found by using dielectric upper layer.
วารสารวิชาการเทคโนโลยีพลังงานและสิ่งแวดล้อม
Journal of Energy and Environment Technology
ปีที่ 2 ฉบับที่ 1 เดือน มกราคม - มิถุนายน 2558
Vol. 1, No. 2, January – June [2015]
Using the two forms of Fish-Bone potential (I and II), a self-consistent calculations are carried out to perform the analysis of binding energies, root mean square radii and form factors using different configuration symmetries of 20Ne nucleus. A computer simulation search program has been introduced to solve this problem. The Hilbert space was restricted to three and four dimensional variational function space spanned by single spherical harmonic oscillator orbits. A comparison using Td and D3h configuration symmetries are carried out.
CONTENTS
INTRODUCTION
CONCEPTS OF WALSH DIAGRAM
APPLICATION IN TRIATOMIC MOLECULES
[IN AH₂ TYPE OF MOLECULES(BeH₂,BH₂,H₂O)]
INTRODUCTION
Arthur Donald Walsh FRS The introducer of walsh diagram (8 August 1916-23 April 1977) was a British chemist, professor of chemistry at the University of Dundee . He was elected FRS in 1964. He was educated at Loughborough Grammar School.
Walsh diagrams were first introduced in a series of ten papers in one issue of the Journal of the Chemical Society . Here, he aimed to rationalize the shapes adopted by polyatomic molecules in the ground state as well as in excited states, by applying theoretical contributions made by Mulliken .
Oxygen Vacancy Conduction in Double PerovskitesMegha Patel
Fuel cells and solar panels provide more environmentally friendly alternatives to burning fossil fuels. Fuel cells currently need better oxygen vacancy conducting cathode materials while solar materials need ways of tuning the band gap. Understanding of oxygen vacancy structure and conduction in perovskites and double perovskites is critical in solving these two challenges. A neutron pair distribution analysis study of the double perovskite Sr2MSbO5.5 (M=Ca, Sr, Ba) found that multiple structures where oxygen vacancies significantly altered the local geometry of the system could explain the same neutron scattering measurements. Our goal is to find all the energetically favored structures in these systems and their impact to oxygen vacancy conduction in these double perovskites. Density functional theory (DFT) with the PBE functional and a generalized gradient approximation (GGA) implementation in the Vienna ab-initio simulation package (VASP) was used to find energies. The conjugate gradient method was used to find minimum energy configurations of the Sr2MSbO6 double perovskites from all 23 possible Glazer octahedral distortions. Oxygen vacancies were introduced without distortions, with trigonal bipyramidal distortions, and with pentagonal distortions. All structures were optimized. The minima featured distorted SbO5 square pyramids and trigonal bipyramids in most systems and sometimes MO7-x pentagonal bipyramidal structures with that structure becoming more favored with increasing ionic size for the M ion. Both of these distortions were suggested by experiment to lead to the neutron scattering measurements. A detailed energetic analysis of these options is presented. Further, implications of these distortions on oxygen vacancy conduction in double perovskite systems are discussed.
SURFACE POLARITONS IN GAAS/ALGAAS/LH HETROJUNCTION STRUCTURE IN A HIGH MAGNET...ijrap
The surface polaritons (SP) variation in Ga As/ Al Ga As/ LH hetrojunction composition in the presence of
a strong transverse quantized magnetic field is estimated using the quantum Hall effect case. The
dispersion characteristics of the SPs are investigated using the dielectric constants values of the Ga As and
the Alx Ga 1-x As media and the defined thickness, the Alx Ga 1-x As medium. The dispersion behaviours
calculated results are listed for considered cases. It was shown that the frequency values against the wave
vector values are affected in a strong manner by changing thickness, of the Alx
Ga 1-x- As media and by
changing the variation of the dielectric constants of Ga As against the Alx Ga 1-x As. The significance
effects of the use of the left-handed (LH) medium as an upper layer of the proposed composition was
demonstrated; the frequency values are remarkably increased using LH material as an upper layer. It was
noticed that at certain conditions of the LH upper layer composition, similar results have been obtained
such as found by using dielectric upper layer.
วารสารวิชาการเทคโนโลยีพลังงานและสิ่งแวดล้อม
Journal of Energy and Environment Technology
ปีที่ 2 ฉบับที่ 1 เดือน มกราคม - มิถุนายน 2558
Vol. 1, No. 2, January – June [2015]
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
MODIFICATION OF DOPANT CONCENTRATION PROFILE IN A FIELD-EFFECT HETEROTRANSIST...msejjournal
In this paper we consider an approach of manufacturing more compact field-effect heterotransistors. The
approach based on manufacturing a heterostructure, which consist of a substrate and an epitaxial layer
with specific configuration. After that several areas of the epitaxial layer have been doped by diffusion or
ion implantation with optimized annealing of dopant and /or radiation defects. At the same time we introduce
an approach of modification of energy band diagram by additional doping of channel of the transistors.
We also consider an analytical approach to model and optimize technological process.
Reference,
https://en.wikipedia.org/wiki/Term_symbol
James E. Huheey, Ellen A. Keiter, Richard L.Keiter and Okhil K. Medhi, Inorganic Chemistry, Principles of Structure and Reactivity. 4th Edn. Pearsons
Reduction of Side Lobes by Using Complementary Codes for Radar ApplicationIOSR Journals
The analysis of new types of Complementary direct sequence complex signals which have synthesized
with well – know code sequences like Barker, Walsh, Golay, and complementary codes. Build on the
autocorrelation function (ACF) and ambiguity function (AF) of signals, the numerical method estimates the
volume of side lobes separately for each signal. The results obtained show that the signals, which have a low
volume of side lobes, means of approximately zero in by using complementary codes with compare to different
codes
The electronic band parameters calculated by the Triangular potential model f...IOSR Journals
This work reports on theoretical investigation of superlattices based on Cd1-xZnxS quantum dots
embedded in an insulating material. This system, assumed to a series of flattened cylindrical quantum dots with
a finite barrier at the boundary, is studied using the triangular potential. The electronic states and the effective
mass of 1 Γ miniband have been computed as a function of inter-quantum dot separation for different zinc
compositions. Calculations have been made for electrons, heavy holes and light holes. Results are discussed and
compared with those of the Kronig-Penney and sinusoidal potentials
A Study On Psychological Variables On Women Sports Participation Levels In Un...IOSR Journals
Abstract: This research is to examine whether the psychological variable on women have any impact on
women’s sports participation between Anna and Pondicherry Universities at different levels. The subject were
(was) randomly selected from Anna University in Tamil Nadu State (300 Players) and Pondicherry University
(Central University) in Puducherry State (300 Players), India. The selected subjects were with a brief
questionnaire, to find out their level of sports participation, anxiety, aggression and stress. Data obtained were
subjected to find out statistical significance among the means using 3 (levels – Zonal, Inter – Zonal and
University participations) X 2 (University – Anna and Pondicherry) Factorial analysis. The result proved that
there were significant differences in selected psychological factors of the different level of women sports
players. There was no significant difference in stress at different levels. There was no significant difference
between the Anna and Pondicherry in anxiety, aggression and stress of the women sports players. It was
concluded that anxiety, aggression, and stress play a vital role in the participation level of women players.
Key Worlds: Different Level of Players, Women Sports Participation, University, Anxiety, Aggression and
Stress
Old wine in new wineskins: Revisiting counselling in traditional Ndebele and ...IOSR Journals
The institution of counselling is present in all human communities as people share their sorrows,
mentor, empower and advise each other. The service of advising and grooming is all that counselling is. This
paper seeks to explore the institution of counselling in Shona and Ndebele traditional societies before the advent
of western formalised counselling institutions. The research sets to prove that counselling is not a new
phenomenon in these societies, that is a remnant of colonialism but rather it is an old institution that has been
window dressed with western strategies and formalisms. African traditional counselling strategies as seen in the
Shona and Ndebele examples emphasise more on the preventive forms of counselling than crisis counselling.
Advice and mentoring are prioritised in these societies as a way of helping people stay out of trouble that in
future will require therapeutic or crisis counselling. Modern day counselling has been professionalised and
commercialised and requires people to pay for it yet in Shona and Ndebele traditional societies it was part of
one’s responsibility to make sure others are well advised and counselled if they are emotionally troubled.
Professional counselling in marriage, carrier guidance, teenage grooming for example is not a new practice but
an old practice done differently like old wine in new wineskins.
A Comparative Study on Balance and Flexibility between Dancer and Non-Dancer ...IOSR Journals
Abstract: Dance is a form of art that normally involves rhythmic movement of the body and accompanied with
music. Movement of human body while performing dance can become a significant medium for communication,
feelings and emotions. It embraces movement, creation and performance. Dance helps to extend the limits of
human physical ability, expressiveness and spirit. When it comes to health dance can be a very effective way of
establishing a lasting healthy living. Anecdotally it can be said that dance potentially motivate and excite young
people. Dance is a non-competitive form of exercise which has positive effects on physical and mental health.
Young girls can be engaged in physical activity through dance. The author being a dancer in fervor and passion
as well as an aspirant of the profession Physical Education strived to conduct the study bearing the title “A
Comparative Study on Balance and Flexibility between Dancer and Non-Dancer Girls”. The researcher
selected 30 girls who are regularly involved in Dance and 30 girls who are non-dancer or rather sedentary on
the basis of purposive stratified random sampling from Bidhan Govt. Girl’s School, Dist. Nadia West Bengal as
the subjects of her study. She incorporated Sit and Reach test and Stork Stand Balance tests for assessment of
Flexibility and Balance respectively. With respect to data analysis initially descriptive statics like mean SD and
range and further paired sample T test was conducted to ascertain the degree of difference between the means
with the help of SPSS soft ware. Data analysis proved significant difference between the Dancer and NonDancer
girls both with respect to flexibility and Balance. In both the cases the Dancer girls proved to be better
though the differences were not statistically significant. Thus the author arrived at the conclusion that dance
involving passion, strength, stamina, enthusiasm, rhythm, amusement and many more could be a wonderful
fitness activity similar to other fitness activities like jogging, running, cycling, swimming etc.
Key words: Dance, Flexibility, Balance, Dancer, Non-Dancer.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
MODIFICATION OF DOPANT CONCENTRATION PROFILE IN A FIELD-EFFECT HETEROTRANSIST...msejjournal
In this paper we consider an approach of manufacturing more compact field-effect heterotransistors. The
approach based on manufacturing a heterostructure, which consist of a substrate and an epitaxial layer
with specific configuration. After that several areas of the epitaxial layer have been doped by diffusion or
ion implantation with optimized annealing of dopant and /or radiation defects. At the same time we introduce
an approach of modification of energy band diagram by additional doping of channel of the transistors.
We also consider an analytical approach to model and optimize technological process.
Reference,
https://en.wikipedia.org/wiki/Term_symbol
James E. Huheey, Ellen A. Keiter, Richard L.Keiter and Okhil K. Medhi, Inorganic Chemistry, Principles of Structure and Reactivity. 4th Edn. Pearsons
Reduction of Side Lobes by Using Complementary Codes for Radar ApplicationIOSR Journals
The analysis of new types of Complementary direct sequence complex signals which have synthesized
with well – know code sequences like Barker, Walsh, Golay, and complementary codes. Build on the
autocorrelation function (ACF) and ambiguity function (AF) of signals, the numerical method estimates the
volume of side lobes separately for each signal. The results obtained show that the signals, which have a low
volume of side lobes, means of approximately zero in by using complementary codes with compare to different
codes
The electronic band parameters calculated by the Triangular potential model f...IOSR Journals
This work reports on theoretical investigation of superlattices based on Cd1-xZnxS quantum dots
embedded in an insulating material. This system, assumed to a series of flattened cylindrical quantum dots with
a finite barrier at the boundary, is studied using the triangular potential. The electronic states and the effective
mass of 1 Γ miniband have been computed as a function of inter-quantum dot separation for different zinc
compositions. Calculations have been made for electrons, heavy holes and light holes. Results are discussed and
compared with those of the Kronig-Penney and sinusoidal potentials
A Study On Psychological Variables On Women Sports Participation Levels In Un...IOSR Journals
Abstract: This research is to examine whether the psychological variable on women have any impact on
women’s sports participation between Anna and Pondicherry Universities at different levels. The subject were
(was) randomly selected from Anna University in Tamil Nadu State (300 Players) and Pondicherry University
(Central University) in Puducherry State (300 Players), India. The selected subjects were with a brief
questionnaire, to find out their level of sports participation, anxiety, aggression and stress. Data obtained were
subjected to find out statistical significance among the means using 3 (levels – Zonal, Inter – Zonal and
University participations) X 2 (University – Anna and Pondicherry) Factorial analysis. The result proved that
there were significant differences in selected psychological factors of the different level of women sports
players. There was no significant difference in stress at different levels. There was no significant difference
between the Anna and Pondicherry in anxiety, aggression and stress of the women sports players. It was
concluded that anxiety, aggression, and stress play a vital role in the participation level of women players.
Key Worlds: Different Level of Players, Women Sports Participation, University, Anxiety, Aggression and
Stress
Old wine in new wineskins: Revisiting counselling in traditional Ndebele and ...IOSR Journals
The institution of counselling is present in all human communities as people share their sorrows,
mentor, empower and advise each other. The service of advising and grooming is all that counselling is. This
paper seeks to explore the institution of counselling in Shona and Ndebele traditional societies before the advent
of western formalised counselling institutions. The research sets to prove that counselling is not a new
phenomenon in these societies, that is a remnant of colonialism but rather it is an old institution that has been
window dressed with western strategies and formalisms. African traditional counselling strategies as seen in the
Shona and Ndebele examples emphasise more on the preventive forms of counselling than crisis counselling.
Advice and mentoring are prioritised in these societies as a way of helping people stay out of trouble that in
future will require therapeutic or crisis counselling. Modern day counselling has been professionalised and
commercialised and requires people to pay for it yet in Shona and Ndebele traditional societies it was part of
one’s responsibility to make sure others are well advised and counselled if they are emotionally troubled.
Professional counselling in marriage, carrier guidance, teenage grooming for example is not a new practice but
an old practice done differently like old wine in new wineskins.
A Comparative Study on Balance and Flexibility between Dancer and Non-Dancer ...IOSR Journals
Abstract: Dance is a form of art that normally involves rhythmic movement of the body and accompanied with
music. Movement of human body while performing dance can become a significant medium for communication,
feelings and emotions. It embraces movement, creation and performance. Dance helps to extend the limits of
human physical ability, expressiveness and spirit. When it comes to health dance can be a very effective way of
establishing a lasting healthy living. Anecdotally it can be said that dance potentially motivate and excite young
people. Dance is a non-competitive form of exercise which has positive effects on physical and mental health.
Young girls can be engaged in physical activity through dance. The author being a dancer in fervor and passion
as well as an aspirant of the profession Physical Education strived to conduct the study bearing the title “A
Comparative Study on Balance and Flexibility between Dancer and Non-Dancer Girls”. The researcher
selected 30 girls who are regularly involved in Dance and 30 girls who are non-dancer or rather sedentary on
the basis of purposive stratified random sampling from Bidhan Govt. Girl’s School, Dist. Nadia West Bengal as
the subjects of her study. She incorporated Sit and Reach test and Stork Stand Balance tests for assessment of
Flexibility and Balance respectively. With respect to data analysis initially descriptive statics like mean SD and
range and further paired sample T test was conducted to ascertain the degree of difference between the means
with the help of SPSS soft ware. Data analysis proved significant difference between the Dancer and NonDancer
girls both with respect to flexibility and Balance. In both the cases the Dancer girls proved to be better
though the differences were not statistically significant. Thus the author arrived at the conclusion that dance
involving passion, strength, stamina, enthusiasm, rhythm, amusement and many more could be a wonderful
fitness activity similar to other fitness activities like jogging, running, cycling, swimming etc.
Key words: Dance, Flexibility, Balance, Dancer, Non-Dancer.
Prediction of Consumer Purchase Decision using Demographic Variables: A Study...IOSR Journals
The demographic environment is of major interest to marketers because it involves people and people make up market. Fragmentation of the mass market into numerous micro markets differentiated by age, sex, education, life style, geography and so on. Because each group has strong preferences and consumer characteristics that can be easily reached through increasingly targeted communication and distribution channels. Most of marketers’ strategic decision making heavily depend on the demographic variables of people in the region where they focus on marketing their products. This study makes known the vital demographic structure of premium car owners in Chennai city and provides models for predicting the consumer’s decision to buy a car when his exact demographic profile is known. The relationship established between the demographic variables and the different stages of consumer’s purchase decision process further helps identifying the significant demographic variables. This will be definitely helpful to the marketers of cars to know their target group and to evolve marketing strategies to make them becoming a car owner.
Implementation of Vertical Handoff Algorithm between IEEE 802.11 WLAN & CDMA ...IOSR Journals
Wireless communications is the fastest growing segment of the communications industry. Everyone
wants the quality of services anytime & anywhere. Wireless networks can integrate various heterogeneous radio
access technologies as GSM, WLAN, Wimax etc. WiMAX is an IP based, wireless broadband access technology
that provides performance similar to 802.11/Wi-Fi networks with the coverage and QOS (quality of service) of
cellular networks. WiMAX is also an acronym meaning "Worldwide Interoperability for Microwave Access
(WiMAX). The main promise of interconnecting these heterogeneous networks is to provide high performance in
achieving a high data rate and support real time applications. These services require various networks (such as
CDMA2000 and Wireless LAN) to be integrated into IP-based networks, which further require a seamless
vertical handoff to 4th generation wireless networks. When a mobile host (MH) changes its point of attachment,
its IP address gets changed. MH should be able to maintain all the existing connections using the new IP
address. This process of changing a connection from one IP address to another one in IP network is called
handoff. Vertical handoff is switching from one network to another while maintaining the session. Vertical
Handoff (VHO) is a major concern for different heterogeneous networks. VHO can be user requested or based
on some criteria already designed by the researcher of that particular algorithm. The main objective is to
implement efficient & effective handoff scheme between two heterogeneous network ie. 802.11 WLAN &
CDMA
CRYSTALLOGRAPHIC AND MORPHOLOGICAL STUDY OF SODIUM ZIRCONIUM PHOSPHATE AS A H...EDITOR IJCRCPS
Sodium zirconium phosphate (NZP) is a potential material for immobilization of nuclear effluents. The Structure of polycrystalline
phase of barium containing NZP was determined on the basis of crystal data of solid state simulated waste forms. The crystal
structure of Na1-xBax/2Zr2P3O12 (x=0.1-1.0) has been investigated using General Structure Analysis System (GSAS) programming.
The BaNZP phase crystallizes in the space group R-3c and Z=6. Powder diffraction data have been subjected to Rietveld
refinement to arrive at a satisfactory structural convergence of R-factors. The unit cell volume and polyhedral (ZrO6 and PO4)
distortion increases with rise in the mole % of Ba2+ in the NZP matrix. SEM, TEM and EDX analysis provide analytical evidence of
barium in the matrix.
Keywords: Ceramic; powder XRD; Rietveld refinement; SEM; nuclear waste immobilization.
Microstructural and Dielectric Characterization of Sr doped Ba(Fe0.5Ta0.5)O3 ...theijes
Solid state reaction method was used to synthesize Ba1-xSrx(Fe0.5Ta0.5)O3 ceramic(x=0, 0.1, 0.2, 0.3, 0.4 and 0.5). The raw materials of making Sr doped Ba(Fe0.5Ta0.5)O3 were BaCO3, SrCO3, Fe2O3, Ta2O5 (purity better than 99%). Pellet and ring shaped samples prepared from each composition were sintered at 1400 and 1450ºC for 5 hour. The phase formation of Ba1-xSrx(Fe0.5Ta0.5)O3 was checked using X-ray diffraction (XRD) technique and observed a cubic perovskite crystal structure in space group Pm3m (221). Microstructure of the individual compound was examined by the field emission scanning electron micrograph (FESEM). Grain size was found to be varied with Sr content. The lattice parameter decreased with increasing Sr content. Dielectric spectroscopy was applied to investigate the electrical properties of BSFT at room temperature and in a frequency range of 100Hz–100 MHz. An analysis of the dielectric constant εʹ and loss tangent tan with frequency was performed assuming a distribution of relaxation times. The low frequency dielectric dispersion corresponds to the DC electrical conductivity.
Thermal and spectroscopy studies of Ag2SO4 and LiAgSO4IOSR Journals
A comparative study is conducted on the structure, electronic and spectroscopic properties of Ag2SO4 and LiAgSO4. Both the sulphates crystallise in an orthorhombic structure with the same space group of Fddd (70). A red shift in Raman modes indicates the stiffness of the crystal Ag2SO4 over LiAgSO4. From ESR, it is observed that these sulphates has Mn2+ impurities leading to the gav= 2.1040 at a field of 3255 G. This indicates that the Mn2+ ions have an environment close to octahedral symmetry. The g value corresponding to Ag2SO4 is 2.3005. The endothermic peaks in LiAgSO4 at 388.8 and 4200C are due to the formation of BCC structure of LiAgSO4. The peak at 420.90C in Ag2SO4 may be due to the phase transition of β-Ag2SO4 particles to α-Ag2SO4 on heating.
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
The papers for publication in The International Journal of Engineering& Science are selected through rigorous peer reviews to ensure originality, timeliness, relevance, and readability.
Theoretical work submitted to the Journal should be original in its motivation or modeling structure. Empirical analysis should be based on a theoretical framework and should be capable of replication. It is expected that all materials required for replication (including computer programs and data sets) should be available upon request to the authors.
CLASSICAL AND QUASI-CLASSICAL CONSIDERATION OF CHARGED PARTICLES IN COULOMB F...ijrap
On the basis of the theory of bound charges the calculation of the motion of the charged particle at the
Coulomb field formed with the spherical source of bound charges is carried out. Such motion is possible in
the Riemanniam space-time. The comparison with the general relativity theory (GRT) and special relativity
theory (SRT) results in the Schwarzshil'd field when the particle falls on the Schwarzshil'd and Coulomb
centres is carried out. It is shown that the proton and electron can to create a stable connection with the
dimensions of the order of the classic electron radius. The perihelion shift of the electron orbit in the
proton field is calculated. This shift is five times greater than in SRT and when corrsponding substitution of
the constants it is 5/6 from GRT. By means of the quantization of adiabatic invariants in accordance with
the method closed to the Bohr and Sommerfeld one without the Dirac equation the addition to the energy
for the fine level splitting is obtained. It is shown that the Caplan's stable orbits in the hydrogen atom
coincide with the Born orbits.
Theoretical investigation of the Structure Activity Relationships (SARs) of a...IJERA Editor
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Half-metallic-ferrimagnetic Sr2CrWO6 and Sr2FeReO6 materials for room temperature spintronics: Linear muffin-tin orbital studies
1. IOSR Journal of Applied Physics (IOSR-JAP)
e-ISSN: 2278-4861.Volume 5, Issue 5 (Jan. 2014), PP 26-30
www.iosrjournals.org
www.iosrjournals.org 26 | Page
HHaallff--mmeettaalllliicc--ffeerrrriimmaaggnneettiicc SSrr22CCrrWWOO66 aanndd SSrr22FFeeRReeOO66 mmaatteerriiaallss
ffoorr rroooomm tteemmppeerraattuurree ssppiinnttrroonniiccss:: LLiinneeaarr mmuuffffiinn--ttiinn oorrbbiittaall
ssttuuddiieess
M. Musa Saad H.-E., I. B. I. Tomsah, and A. Fiasal Elhag
Department of Physics, College of Science, Qassim University, Buraidah 51452, Kingdom of Saudi Arabia
AAbbssttrraacctt:: Complex perovskite-like materials which include magnetic transition elements have relevance due to
the technological perspectives in the spintronics industry. In this work, we report the studies of the electronic
and magnetic characterizations of Sr2CrWO6 and Sr2FeReO6 as spintronics materials at room temperature by
using the linearized muffin-tin orbitals (LMTO) method through the atomic-sphere approximation (ASA) within
the local spin density approximation (LSDA). The interchange-correlation potential was included through the
LSDA+U technique. The band structure results at room-temperature predict half-metallic ferrimagnetic ground
state for Sr2CrWO6 and Sr2FeReO6 with total magnetic moment of 1.878 μB and 3.184 μB per formula unit,
respectively, agreement with the previous theoretical and experimental results.
Keywords: Complex perovskite; LMTO-ASA method; Half-metallic.
II.. IInnttrroodduuccttiioonn
Complex perovskite oxides have the general chemical formula of A2BB'O6, crystalline in the rock-salt
(Na+
Cl–
) structure with alternate perovskites ABO3 and AB'O3 along three crystallographical axes [1]. The
corners of each perovskite unit cell are in turn occupied by different transition-metals B and B', have the mixed
valence state (BB')8+
,with oxygen atoms located in between, forming alternate BO6 and B'O6 octahedra [1-2].
The large alkaline-earth metal A2+
occupied the body-centered site with 12-fold oxygen coordination in each
unit cell [3]. The long-range superexchange interactions between magnetic ions in complex perovskite A2BB'O6
are in the form (– B – O – B' –) instead of double-exchange (– B – O – B –) in single perovskite ABO3 [4], [5].
Materials with high spin-polarization of the conducting charge carriers, the current, have attracted a
great deal of attention owing to their technological applications in spin-electronics (spintronics) [6], in
magnetotransport devices, as well as their rich and challenging physical properties [1-6]. In particular, an ideal
material with 100% spin-polarization is described as half-metal [7]. Such materials can be found in several
materials classes as in; magnetite Fe3O4 [8], CrO2 [9], LaMnO3 [10], Heusler alloy Co2(Cr1-xFex)Al [11], [12], as
well as, in the group of complex perovskites [1],[4-5]. Complex perovskites are of special attention, since within
this group half-metals with above room-temperature (RT) transition temperatures are found, such as in
A2FeMoO6 (A = Ca, Sr, Ba) [13-14] and Sr2CrMoO6 [13],[15]. Ordered complex perovskites Sr2FeMoO6,
Sr2FeReO6, Sr2CrWO6, etc., are among the very few materials that allow electrons of one spin direction to move
through them as though they were passing through a normal metal, while blocking electrons of the opposite
spin. Materials that behave this way at RT are even more exotic, so their conduction bands have fully spin-
polarized [1]. Sr2FeReO6, Sr2CrWO6 complex perovskites, in particular, have attracted more attention due to
their fairly high transition temperature from a paramagnetic to ferrimagnetic state, which makes them and their
family of materials candidates for future spintronics applications.
IIII.. MMaatteerriiaallss CChhaarraacctteerriizzaattiioonn
In the present work we report systematic studies on the Cr/Fe (3d) and W/Re (5d) orbitals contributions
to the electronic and magnetic structures of two close relative members of strontium complex perovskite oxides
Sr2CrWO6 and Sr2FeReO6. Where, W and Re are neighboring 5d transition-metal elements in the periodic table
with the ordinary electronic configurations of [Xe] 4f14
5dn
6s2
, where n = 4 for W (Z = 74) or n = 5 for Re (Z =
75), where [Xe] denotes the configurations of the Nobel-gas Xenon core. For chromium and iron Cr/Fe (3d), Cr
has an odd electron configuration of [Ar] 4s1
3d5
owing to the lower energy of the high spin configuration, not
[Ar] 4s2
3d4
as it might expect, where a half-filled d sub-level is more energetically favorable than a half-filled s
sub-level, so one of the 4s electrons is promoted to a 3d orbital. On the other hand, iron (Fe) has an ordinary
electron configuration of [Ar] 4s2
3d6
. Cr and Fe exhibit a wide range of possible oxidation states, where the +3
state is more stable energies [16-18]. Accordingly, the valence configurations of transition-metal ions in
Sr2CrWO6 are; Cr3+
(3d3
) and W5+
(5d1
) in the high spin state with valence spin magnetic moments of S = 3/2
and S = 1/2 according to Hund's rule, respectively. Consequently, the theoretical total magnetic moment is 2.0
μB per formula unit cell for the ferrimagnetic ground state. In Sr2FeReO6, Fe3+
(3d5
) in the high spin state with S
2. Half-metallic-ferrimagnetic Sr2CrWO6 and Sr2FeReO6 materials for room temperature spintronics:
www.iosrjournals.org 27 | Page
= 5/2 and Re5+
(5d2
) is highly ionized with valence spin magnetic moment of S = 1. As a result, the total
magnetic moment for the ferrimagnetic ground state is 3.0 μB per Sr2FeReO6.
For cubic Sr2CrWO6 and Sr2FeReO6 complex perovskites with space group Fm-3m (No. 225), we used the
experimental lattice constants of a = 7.890 Å from (Ref. 19) and a = 7.832 Å from (Ref. 1), respectively, closed
to the theoretical values calculated using SPuDS [18] 7.880 Å and 7.886 Å, correspondingly. The magnetic
structure in complex perovskites can be assigned to the AFM superexchange interactions between two very
different transition magnetic ions [1],[17], such as Cr/Fe (3d) and W/Re (5d), in this work, via intermediated O2-
ions (Cr/Fe – O – W/Re). In addition to, the naturally small magnetic moment at W/Re (5d) is believed to be not
intrinsic but is induced by the strong magnetic ions Cr/Fe (3d).
IIIIII.. CCaallccuullaattiioonn mmeetthhooddss
The first-principles linear muffin-tin orbital (LMTO) method with atomic-sphere approximation (ASA) has
been employed to perform self-consistent band structure calculations within the local spin density
approximation (LSDA). In LMTO-ASA, which is similar to the multiple-scattering Korringa-Kohn-Rostoker
(KKR) method [20] , the potential is approximated by a muffin tin potential, i.e., it is spherically symmetric
around the atomic sites and constant in the interstitial volume. Moreover, ASA takes the one-electron potential
and charge density to be spherically symmetric inside space-filling Wigner-Seitz (WS) spheres whose overlap is
neglected, the interstitial volume, now integrating to zero [20]. The von Barth–Hedin parameterization for
exchange-correlation potential is used in the calculations [1], [17]. The Hartree potential is expanded in term of
spherical harmonic up to 6, therefore, Sr (5s 4p 4d), Cr/Fe (4s 4p 3d), Mo (5s 5p 4d), W (6s 6p 5d) and O (2s
2p) LMTOs were input as valence states, while Sr (4s), Cr/Fe (3p), Mo (4s 4p), W (5p 4f) fixed as semicore
states in the unit cells. It has been established that the structures are close enough, that no empty sphere (ES) is
needed to introduce the unit cells [1]. The numbers of divisions along a reciprocal lattice vector which will set
up the mesh for integrating valence state are selected as (6 × 6 × 6). Special k points of 50 in the irreducible
Brillouin zone (IBZ) were used in band structure and density of states calculations. A single kappa LMTOs
basis set is expanded in spherical harmonic up to the angular momentum l max = 6, was used for the valence-band
charge densities and potential inside the non-overlapping muffin-tin spheres [20]. The interchange-correlation
potential was included through the LSDA+U technique, where the on-site Coulomb energy (U) has been in
used. The correlation parameters, Coulomb energy (U) and Hund's rule exchange (J), were utilized for strongly
correlated 3d and weakly 5d electrons in the calculations. The Hubbard parameters (U = 4.0 eV, J = 0.98 eV)
are used for Cr/Fe (3d) states (Refs. 1.0 and 17), even as (U = 1 eV, J = 0.96 eV) are used for W/Re (5d) states
(Refs. 1 and 17). The resolving of spin up and down in total and partial densities of states for Sr2CrWO6 and
Sr2FeReO6 were calculated and obtained from the LSDA+U calculations.
IIVV.. RReessuullttss aanndd DDiissccuussssiioonn
Fig. 1 illustrates the total densities of states (TDOSs) of Sr2CrWO6 and Sr2FeReO6 from band structure
LSDA+U calculations. The obtained results of Sr2CrWO6 and Sr2FeReO6 are in agreement with previous
LSDA+U calculations [1],[17],[22]. In spin-up TDOSs, there are energy gaps of about 1.33 eV in Sr2CrWO6
and 2.18 eV in Sr2FeReO6 between the occupied Cr/Fe (3d) and unoccupied W/Re (5d) partial bands. Since the
energy gap in the spin-up produces from the antiferromagnetic coupling between Cr/Fe (3d) and W/Re (5d)
states, as shown in Fig. 2, this situation emerges as peaks of 3d and 5d bands polarized antiferromagnetically
demonstrate the Cr/Fe (3d) ↑ and W/Re (5d) ↓ form. Therefore, the spin-up electrons are insulating while the
spin-down electrons are metallic, resulting in full (100%) spin-polarized of the conduction electrons at EF. For
that reason, Sr2CrWO6 and Sr2FeReO6 materials allow electrons of spin-down direction to move through them
as though they were passing through a metal, while blocking electrons of the spin-up.
Fig. 1. Total density of states (TDOS) for (a) Sr2CrWO6, and (b) Sr2FeReO6
3. Half-metallic-ferrimagnetic Sr2CrWO6 and Sr2FeReO6 materials for room temperature spintronics:
www.iosrjournals.org 28 | Page
Fig. 2. Total and partial densities of states for (a) Sr2CrWO6, and (b) Sr2FeReO6
As seen in Fig. 2, the conduction bands in spin-down orientation is attributed mainly to the
contributions of W (5d) and Re (5d) ions with tiny contributions of Cr (3d) and Fe (3d), correspondingly.
Compare the TDOSs with PDOSs, the level distributions in of Sr2CrWO6 and Sr2FeReO6 are overall very
similar, except a peak between 1.0 eV and 3.0 eV, above EF, is higher in Sr2FeReO6 than in Sr2CrWO6. This
dissimilarity, as seen in Fig. 2, due to the extra electron in Re (5d2
) than in W (5d1
).
In order to understand in some more detail the origin of the electronic and magnetic characters of
Sr2CrWO6 and Sr2FeReO6, we critically examine the partial electronic density of states (PDOS) of these
systems. The basic critical ingredients in the TDOS are the d states of the Cr/Fe and W/Re atoms, which in turn
are split into t2g and eg states by the octahedral crystal field (OCF) produced by the oxygen octahedra. The t2g
states having lower energy and place for three electrons per spin channel, whereas the eg states are higher in
energy and have places for two electrons per spin channel. Furthermore, due to the exchange splitting, t2g bands
degenerate into double orbitals (dxz and dyz) and one singlet orbital (dxy), while eg bands degenerate into two
singlet orbitals (dx2–y2 and dz2), as seen in Fig. 3, which show the partial densities of states of t2g, eg and 2p
orbitals in Sr2CrWO6 and Sr2FeReO6.
From the PDOS in Fig.3 (a), the threefold degenerate Cr t2g states of the spin-up channel are filled Cr3+
(3d3
: t2g
3
↑); consequently the dxy↑, dxz↑ and dyz↑ orbitals are at the energy range, about –7 eV ~ –1.5 eV in the
valance bands. Therefore, the EF ends up in the CF gap of ∆o ≈ 1.5 eV between Cr t2g and eg states. A similar
situation is observed in the half-metallic close-relative Sr2FeReO6 [21], [22]. Due to the antiferromagnetic
coupling in Cr (3d) – W (5d), it is the spin-down channel in W (5d) which is the occupied one, and it contains
one electron in t2g states W5+
(5d1
: t2g
1
↓). This means that the W (5d) t2g spin-down states are only filled to about
one-two, resulting in high density of states of dxy and dyz at the EF in spin-down channel. In addition to, due to
hybridization between states in Sr2CrWO6, Cr t2g↓ states achieved small occupation, while W (5d) states in the
spin-up channel are essentially empty; hybridization with Cr t2g↑ states results nevertheless in a finite, small
occupation above EF.
Fig. 3. Partial densities of states of t2g, eg and 2p orbitals in (a) Sr2CrWO6, and (b) Sr2FeReO6
4. Half-metallic-ferrimagnetic Sr2CrWO6 and Sr2FeReO6 materials for room temperature spintronics:
www.iosrjournals.org 29 | Page
On the other hand, from the PDOS in Fig.3 (b), the Fe t2g and eg states are full-filled in the spin-up
orientation; Fe3+
(3d5
: t2g
3
↑ eg
2
↑) in the high spin state; the electronic configuration can be set of orbitals as
(dxy↑)1
, (dxz↑ and dyz↑)2
, (dx2 –y2)1
and (dz2)1
extend from –8.0 eV to -2.0 eV in the valence bands. The exchange
splitting is about 7.5 eV, larger than the CF splitting, ∆o ≈ 2.25 eV, resulting in the high-spin of Fe (3d) states.
At the same time, spin-down channel in Re (5d) which is the occupied one, and it contains two electrons in t2g
states Re5+
(5d2
: t2g
2
↓). Therefore, the Re t2g spin-down states are only filled to about two-three, emerged as a
high spin-down DOS of dxy and dyz at EF. Inversely, neither Fe t2g↓ nor Re (5d)↑ states have contributed to the
bands around EF, while the O (2p) bands are at a much lower energy from –9.0 to –2.0 eV.
Finally, the magnetic structure in Sr2CrWO6 and Sr2FeReO6 complex perovskites can be assigned to
the antiferromagnetic superexchange interactions between Cr/Fe (3d) and W/Re (5d) via intermediated oxygen
atoms in the 180o
long-chain Cr (3d-t2g↑) – O (2pπ) – W (5d-t2g↓) and Fe (3d-t2g↑) – O (2pπ) – Re (5d-t2g↓),
correspondingly. The calculated spin magnetic moments from LSDA+U for Sr2CrWO6 are; 2.919 μB for Cr, –
1.044 μB for W with a total magnetic moment of 1.878 μB, which is 94% agreement with the later LSDA+U
result, 2.01 μB [18], [22]. For Sr2FeReO6, 4.578 μB for Fe, –1.344 μB for Re, and the total magnetic moment
found to be 3.184 μB, also, agree to the LSDA+U result, 3.06 μB [1]. The bands scheme for both compounds are
illustrated in Fig. 4, the results can be resumed by means the simple model describes the effect of filling t2g and
eg orbitals in 3d and 5d bands for spin-up and spin-down configurations.
Fig. 4. Representation of the electronic density of spin-up (↑) and spin-down (↓) states in 100% electronic spin-
polarized half metal in the Sr2CrWO6 and Sr2FeReO6 materials. The quantity of filling signifies the effect of t2g
and eg orbitals in 3d and 5d bands per unit volume and per unit energy E. EF is the Fermi energy.
VV.. CCoonncclluussiioonn
We have comparatively studied the electronic and magnetic characterizations of complex perovskites
Sr2CrWO6 and Sr2FeReO6 by using the linearized muffin- tin orbitals through the atomic-sphere approximation
method within the local spin density approximation, including the interchange-correlation potential through the
LSDA+U technique. The band structure results demonstrated half-metallic ferrimagnetic ground state for
Sr2CrWO6 and Sr2FeReO6 with total magnetic moment of 1.878 μB and 3.184 μB per formula unit, respectively,
in exact agreement with the theoretical and experimental results. The obtained HM-FiM feature in complex
perovskites Sr2CrWO6 and Sr2FeReO6 makes these materials suitable for many applications. It established that
they have a high degree of electronic spin-polarization which means that they will have the potential spin
transport electronics (spintronics), where spin currents are utilized as well as charge currents.
AAcckknnoowwlleeddggmmeennttss
The authors gratefully acknowledge financial support from the Deanship of Scientific Research,
Qassim University in KSA, under the Grant Name Research-backed research priorities for the year 1432 – 1433
AH, and Project Number 1622.
Cr t2g
3
Cr eg
0
W t2g
1
E
E
Spin
Fe eg
2
Fe t2g
3
Re t2g
2
EF
5. Half-metallic-ferrimagnetic Sr2CrWO6 and Sr2FeReO6 materials for room temperature spintronics:
www.iosrjournals.org 30 | Page
RReeffeerreenncceess
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