this is a ppt on Diluted magnetic semiconductor

1. THEORETICAL STUDY OF ELECTRONIC
AND MAGNETIC PROPERTIES OF RARE
EARTH DOPED TIN TELLURIDE
Guided by
Dr. Sashi sekhar Behera
Presented by
Saptarshi Nayak
P.G. Department of physics
Berhampur University

2. CONTENT
• INTRODUCTION
• OBJECTIVE
• MOTIVATION
• LITERATURE REVIEW
• METHOD OF DATA COLLECTION
• DATA PRESENTATION
• CONCLUSION

3. INTRODUCTION
• SnTe is an interesting material that has drawn current interest ,because of
the possibilities of showing multi-ferroic behavior.
• It is believed to having only p-type conductivity. The p-type shows a variety
of interesting properties that depend on the carrier density.
• These are the low temperature superconductivity and the carrier-
concentration-dependent de Haas-Shubnikov effect.When doped with
manganese and other magnetic impurities, it shows a wide range of
magnetic phases as functions of carrier density.

4. OBJECTIVE
• To study the carrier electronic structure of both n-and p-type PbTe and SnTe
systems using the 𝑘. 𝜋 method. This method is a very useful tool to study
the electronic structure of semiconductors.
• The method was developed and refined by many people as to be applicable
to different systems.
• The pioneering works are due to Dresselhaus et al (DKK model), Kane
(Kane model), Luttinger and Kohn (LK model), Rashba, Bir and Pikus,
Roth et al, Pidgeon and Brown, Chuang and Chang, Pfeffer and Zawadzki
and Tripathi et al.

5. MOTIVATION
• The principle of this method is that if the energy eigen values and the eigen
functions are known at a given k0-point, say ,in the Brillouin zone, then one
can calculate these values at any arbitrary k-point.
• These materials and also their diluted magnetic structures have also been
studied for magnetization with different magnetic impurities.
• The diluted magnetic p-type 𝑆𝑛1−𝑥𝑀𝑛𝑥𝑇𝑒 and 𝑆𝑛1−𝑥𝐺𝑑𝑥𝑇𝑒 materials
exhibit interesting properties like room temp ferromagnetism, magnetic
phase transition ,carrier induced local magnetic moment saturation etc as
functions of external magnetic field, temperature, impurity and carrier
concentrations.

6. MOTIVATION
• In the p-type system, they studied the EPR (Knight ) shift at the 𝑀𝑛+2
site
due to partial polarization of holes in the presence of an applied magnetic
field, resulting from the exchange interaction between the carriers and the
𝑀𝑛+2 moments.

7. LITERATURE REVIEW
• Recently there is an emergence of interest in the magnetism of
semiconductors, and tremendous focus on systems like diluted-magnetic
and semi magnetic semiconductors and phenomenon like spintronics.
• In the latter case the carrier induced magnetism assumes significance. In
this respect, compound semiconductors belonging to IV-VI group like lead
chalcogenides and their solid solutions have been investigated theoretically
by G.S Tripathi et. al. past few years.

8. LITERATURE REVIEW
• The calculations were done for both p and n-type PbX, X = S, Se, Te
and SnTe systems. But, n-type of calculation for SnTe was made for a
hypothetical system because by then there was no experimental
evidence of n-type conductivity in SnTe.
• Recently, however, there was a report that Cr-doped SnTe crystals
have n-type concentration of 5.8 × 1022
𝑐𝑚−3
and room temperature
ferromagnetism with Curie temperature of 294 K. This observation has
made the study of SnTe systems more exciting.

9. METHOD OF DATA COLLECTION
• There are many ways of calculationg Band structures like using
green’s function, Density functional theory etc.
• We are using the 𝑘. 𝜋 method for band calculation which was
developed by Kane. This has to be developed in a two band model.
• The band edge Hamiltonian is diagonalised exactly within the 𝑘. 𝜋
approach.
• Annalytic expression can be observed for energies and wavefunction
if the method is used for two band model i.e. Valance band and
conduction band separated by an energy gap (Eg).

10. DATA PRESENTATION

11. DATA PRESENTATION

12. CONCLUSION
• Finally , we present here a very careful examination and analysis of the
effective g factor in 𝑆𝑛1−𝑥𝐸𝑢𝑥𝑇𝑒 and analysis of the effective g factor in
𝑆𝑛1−𝑥𝐸𝑢𝑥𝑇𝑒 and compare our results with 𝑃𝑏1−𝑥𝐸𝑢𝑥𝑇𝑒 .
• The systematic and trends observed in g values for both materials are good
above the impurity concentration x=0.02.
• However, the trend for the g value is just the opposite well function of x. We
report here huge effective g factor values i.e. g=1028 and g=997 for n-and
p-type 𝑆𝑛1−𝑥𝐸𝑢𝑥𝑇𝑒 respectively.

13. CONCLUSION
• The large g factor accounts for the bandgap tuning and coupling of far-
off bands staying across the gap.
• The huge effective g factor opens up new opportunities for the
development of spin-based devices such as spin FET and filters.

14. REFERENCE
• 1. BeheraS S,Nayak S,Gouda H S,Hota R L,2022,Giant effective g factor and
anisotropy in 𝑆𝑛1−𝑥𝐸𝑢𝑥𝑇𝑒:Contribution from spin-orbit and s/p –f
hybridisation,Current applied physics,42(2022)71-79,Elsevier.
• 2. BeheraS S,TripathyG S,2016,Band gap engineering and 𝑘. 𝜋 electronic
structure of lead and tin tellurides,Mater.Res.Express 3(2016)065903
• 3.Tripathy G S, Dash K, Nayak S K,Behera S N and Entel P 2012 AIP
Conf.Proc.1461 64
• 4.Tripathy G S,Dash K,Behera S N,Nayak S K and Entel P 2013 J.Appl.Phys. 113
103902
• 5. Shadangi S K and Tripathi G S 2016 Semicond. Sci.Technol. 35 03518
• 6. G. Karzewski, J. Furdyna, D. Partin, C. Thrush, J. Heremans, Far-infrared
investigation of band-structure parameters and exchange interaction in
𝑃𝑏1−𝑥𝐸𝑢𝑥𝑇𝑒 films, Phys. Rev. B 46 (20) (1992), 13331.