STRUCTURAL, MAGNETIC AND MÖSSBAUER STUDIES OF Dy2Fe17-xZrx, Dy2Fe16Ga1-xZrx AND Gd2Fe16Ga0.5TM0.5 (TM = Cr, Mn, Co, Ni, Cu, Zn) INTERMETALLIC COMPOUNDS

1. STRUCTURAL, MAGNETIC AND MÖSSBAUER
STUDIES OF Dy2Fe17-xZrx, Dy2Fe16Ga1-xZrx AND
Gd2Fe16Ga0.5TM0.5 (TM = Cr, Mn, Co, Ni, Cu, Zn)
INTERMETALLIC COMPOUNDS
Jiba Nath Dahal
July 12, 2013
Advisor: Professor Sanjay Mishra
Department of Physics, The University of Memphis

2. What is Permanent Magnet?
• The ferromagnetic materials which can be
permanently magnetized and can create own
persistent magnetic fields are called permanent
magnets. Once they are magnetized it is
difficult to demagnetize.
• Soft ferromagnetic materials
have high magnetization but low coercivity.
• Hard ferromagnetic materials
have high coercivity and low magnetization.1
1
0
0
Hc
Mr
Ms

3. Application of Permanent magnet 2
1. Electro-mechanical machine, electric motor,
measurement instruments, current control
devices.
2. Microwave devices, Ion beam control devices.
3. Power tubes, waveguide devices, particle
accelerator, mass spectrometers.
4. NMR imaging devices, surgical clamps and
many more.

4. Magnetic Properties and parameters
Intrinsic Properties:
Saturation magnetization, Curie
temperature and
Magnetocrystalline anisotropy
which are related to the magnetic
structure of the materials.
Magnetic moments and interactions
on the atomic scale helps to
understand intrinsic properties.
Extrinsic Properties: Remanence,
coercivity and energy product
(BH)max which are related to the
microstructure.1
Fig 1: A typical Hysteresis loop of a hard magnet

5. Trend in permanent magnet improvement
• The loadstone was the first permanent magnet
known in ancient time around 600 BC.
• Later in 1931 Alnico magnet was the first
commercially available permanent magnet .3
• RE-TM intermetallic magnets starts after 1966
after the formation of YCo5 by US air force.4

6. Trend in permanent magnet improvement contd…
Fig 2: Development permanent magnet on the basis
of energy product.5
Fig 3: size reduction of Permanent
magnet keeping the same (BH)max
6
C-steel
Nd-Fe-B

7. •Alnico
•Ceramic
•Rare Earth transition metal magnets ( R with TM).
Types of Permanent Magnets

8. Classification of Rare-Earth (R) Magnets
RE atomic numbers from 59-70, ferro/ferrimagnetic, high
magnetic anisotropy (causing the increase in Hc).
Classification:
• RCo5
• NdFeB.
• (R2TM17 ) [TM = Transition Metal]
Each magnet is superior than previously known permanent
magnets.

9. SmCo5
• Rhombohedral
• expensive.
• Tc~ 720 C , Hc ~ 55kOe and (BH)ᵒ max ~ 32 MGOe 2
Nd2Fe14B
• Tetragonal
• better and cheaper permanent magnet materials than SmCo5 .
• Tc ~ 300 C, Hc ~ 25kOe andᵒ (BH)max ~ 52 MGOe. 2
•But Nd is in the verge of extinction.
R2Fe17
• Rhombohedral (Th2Zn17) and hexagonal (Th2Ni17 )structure.
• iron-rich phase in the binary R-Fe alloy implies the highest
magnetization.
•They have Hc ~15kOe and (BH)max ~ 26MGOe and.
•R2Fe17 permanent magnet can dissolve different elements to make
Merits/Demerits of Rare-Earth based Permanent Magnets

10. Curie Temperature plot of different rare-earth based Permanent Magnet
Fig 4: Curie temperature for different series of R-TM intermetallic compounds7

11. Literature Review
• The main drawbacks of R2Fe17 materials are low Curie
temperature and magnetic anisotropies.8
• Substitution of Fe atoms by magnetic atoms such as (Co, Ni, Cr,
Mn), and refractory atoms (Ti, V, Mo, Nb, W, Zr ).
• The substitution of non-magnetic atoms (Al, Ga, Si) at Fe sites
have been reported to increase ferromagnetic coupling which in
turn increases the Curie temperature.8
• Interstitial substitution of non-metals such as C, N and H in
R2Fe17 lattice but are unstable at high temperature.9

12. Rational
Based on the literature review we propose to study:
• Heavier rare-earth based R2Fe17 intermetallics: Heavier R brings in higher
magnetic anisotropy. Also heavy R has higher Bohr Magnetron number.
These can bring enhancement in magnetization of the alloys.
• Substitution of Fe with Zr atoms to change magnetic interaction between
iron atoms. Zr atom (atomic radius 2.06 Å which is bigger than Fe atom
(atomic radius 1.56 Å) can change exchange interaction between iron-iron
atoms due to volume expansion. This changes can bring enhancement in the
Curie temperature of the alloys.
• Substitution of Ga with non-magnetic atom Zr in Dy2Fe16Ga1-xZrx to
understand the role of Zr in Tc enhancement.
• Substitution of Ga with magnetic atoms such as Cr, Mn, Co, Ni, Cu, Zn in
Gd Fe Ga TM to understand the role of TM metal in Tc enhancement.

13. Objective of Research
• To synthesis non-magnetic Zr atom doped on Dy2Fe17-
xZrx and Dy2Fe16Ga1-xZrx intermetallic alloys (x = 0.00,
0.50, 0.75, 1)
• To synthesis magnetic atom doped Gd2Fe16Ga0.5TM0.5 (TM
= Cr, Mn, Co, Ni, Cu, Zn)
• Structural, magnetic, and Mössbauer studies of as
prepared alloys
• To develop understanding on the role of non-magnetic
and magnetic doping in governing the magnetic
properties and Tc of alloys.

14. Synthesis
Sample Preparation
• Preparation of Dy2Fe17-xZrx and Dy2Fe16Ga1-xZrx using
arc melting technique. (x = 0.00, 0.50, 0.75, 1.00)
• Preparation of Gd2Fe16Ga0.5TM0.5 (TM = Cr, Mn,
Co, Ni, Cu, Zn) using arc melting technique.

15. Experimental
Structural
• X-ray diffraction: Crystal Phase and structure.
Magnetic Study
• VSM (Vibrating Sample Magnetometer)
Temperature dependent Magnetic parameters
(saturation magnetization and Curie Temperature)
• Mossbauer Spectrometer: Temperature dependent
Hyperfine filed parameters (hyperfine filed,
isomer shift and quadrupole splitting)

16. Results & Discussions
Effect of non-magnetic Zr atom doped Dy2Fe17-xZrx and Dy2Fe16Ga1-xZrx
Part A

17. Results & Discussions
Fig 6. XRD of Dy2Fe16Ga1-xZrx
Structural
Fig 5. XRD of Dy2Fe17-xZrx
• XRD patterns show that peak is shifting to the left upon Zr substitution. (lattice
Expansion).
• Pure 2:17 phase is obtained for x = 0.50 for Dy2Fe17-xZrx and x = 0.25 for Dy2Fe16Ga1-xZrx.
• At higher concentration of Zr substitution , secondary paramagnetic DyFe3 is reported.
Intensity(a.u.)
706050403020
2θ (degree)
DyFe3
x = 0.00
x = 0.25
x = 0.50
x = 0.75
x = 1.00
42.041.541.040.540.0
2θ (degree)
Intensity(a.u.)
706050403020
2θ (degree)
DyFe3
x = 0.00
x = 0.25
x = 0.50
x = 0.75
x = 1.00

18. Lattice parameter study
2θ (degree)
Fig 7: Rietveld refinement profile for Dy2Fe17
Ionic radii of Dy = 1.03 Å, Zr =0.84
Å Fe = 0.55 Å, Ga = 0.62Å

19. Lattice parameters and unit cell volume of Dy2Fe17-xZrx and Dy2Fe16Ga1-xZrx
• Lattice parameters and unit cell
volume of the compound linearly
increased at the rate of 8.2084
Å3
/Zr and 8.826 Å3
/Zr atom.
• c-axis expansion rate is slightly
greater in Dy2Fe16Ga1-xZrx than in
Dy2Fe17-xZrx.
522
520
518
516
514
V(Å
3
)
1.00.80.60.40.20.0
x, Dy2Fe17-xZrx
8.5
8.4
8.3
c(Å)a(Å)
1.00.80.60.40.20.0
x, Dy2Fe17-xZrx
8.5
8.4
8.3
c(A
o
)a(A
o
)
1.00.80.60.40.20.0
x, Dy2Fe16Ga1-xZrx
522
520
518
516
514
V(Å
3
)
1.00.80.60.40.20.0
x, Dy2Fe16Ga1-xZrx
Dy2Fe17-xZrx Dy2Fe16Ga1-xZrx
x
a
(Å)
c (Å)
V
(Å3
)
a (Å)
c
(Å)
V
(Å3
)
0 8.4554 8.2903 513.30 8.4632 8.2902 514.013
0.25 8.4614 8.2936 515.45 8.4694 8.2892 514.265
0.5 8.4696 8.3044 516.91 8.4843 8.2998 517.221
0.75 8.4749 8.3083 517.72 8.5183 8.3253 519.498
1 8.5382 8.3374 522.42 8.5382 8.3374 522.429
Fig 8: a, c and unit cell volume plot for Dy2Fe17-xZrx Fig 9: a, c and unit cell volume plot for Dy2Fe16Ga1-xZrx

20. Fig 11. Site occupancy of Zr and Ga for Dy2Fe16Ga1-xZrx
Site Occupancy
• Reitveld refinement shows that all 4f, 6g, 12j and 12k Fe-
sites are affected by the addition of Zr.
• Zr is substituting more for Fe atoms at 12j and 12k site.
50
40
30
20
Siteoccupency,(%)
1.00.80.60.40.20.0
x, Dy2Fe17-xZrx
3.0
2.0
1.0
0.0
4f
6g
12j
12k
Fe
Zr
3
2
1
0
Siteoccupency,(%)
1.00.80.60.40.20.0
x, Dy2Fe16Ga1-xZrx
3
2
1
0
4f
6g
12j
12k
Ga
Zr
Fig 10. Site occupancy of Zr and Fe for Dy2Fe17-xZrx

21. 2.8
2.7
2.6
2.5
Bondlength(Å)
1.00.80.60.40.20.0
x, Dy2Fe17-xZrx
4f-4f
6g-12j
6g-12k
12j-12j
12k-12k
2.50
2.48
2.46
2.44
2.42
Bondlength(Å)
1.00.80.60.40.20.0
x, Dy2Fe16Ga1-xZrx
2.8
2.7
2.6
2.5
2.4
Bondlength(Å)
4f-4f
6g-12j
6g-12k
12j-12j
12k-12k
Fig 12.: Bond length for Dy2Fe17-xZrx.
• Maximum change in Fe-Fe bond length is observed to
occur for 6g-12j, 6g-12k and 12j-12j sites which helps to
improve the Fe-Fe interaction to increase Tc.
• The increase in Fe-Fe distance are coming from unit cell
volume expansion.
Fig 13.: Bond length for Dy2Fe16Ga1-xZrx
Bond length

22. Magnetic Studies
• Saturation magnetization of alloys linearly decreased as a function of Zr
substitution.
• Decrease in Ms of Dy2Fe16Ga1-xZrx could be due to the predomination of
positive effect on the magnetic moment caused by the optimum of bond
length over negative effect caused by the magnetic dilution of non-magnetic
substituents.
• Tc increases because of the Fe-Fe strength in Fe-Fe exchange coupling
coming from bond length.
500
480
460
440
420
Tc(K)
1.00.80.60.40.20.0
x, Zr content
Dy2Fe17-xZrx
Dy2Fe16Ga1-xZrx
64
62
60
58
56
54
52
Magnetization,(emu/gm)
1.00.80.60.40.20.0
x, Zr content
Dy2Fe17-xZrx
Dy2Fe16Ga1-xZrx
Fig 14. Saturation Magnetization of Dy2Fe17-xZr x and Dy2Fe16Ga1-xZrx.
Fig 15. Tc plot for Dy2Fe17-xZr x and Dy2Fe16Ga1-xZrx.

23. Mössbauer Studies
Fig 16. Mössbauer spectra of Dy2Fe17-xZrx
• Mössbauer spectra were fitted using WMOSS program
with 3 sextets corresponding to Fe atoms at 4 sites.
• Paramagnetic DyFe3 phase was detected in the
Mössbauer spectra. The contribution of DyFe3
paramagnetic phase goes increasing with increasing the
Zr content.
• Hyperfine field parameters decreases with due to
decrease in magnetic moment of Fe atom
• Isomer shift increases due to the unit cell volume
expansion.
Dy2Fe16Zr1
-10 -5 0 5 10
Velocity (mm/sec)
Dy2Fe17
Dy2Fe16.75Zr0.25
Dy2Fe16.5Zr0.5
Dy2Fe16.25Zr0.75
Absorption(%)
260
240
220
200
180
HF(kOe)
4f
4e
6g4
6g2
12j8
12j4
12k8
12k4
-0.3
-0.2
-0.1
0.0
0.1
0.2
IS(mm/sec)
1.00.80.60.40.20.0
x, Dy2Fe17-xZrX
4f
4e
6g
12j
12k
Fig 17. RT Bhf and IS for Dy2Fe17-xZrx

24. -10 -5 0 5 10
Velocity (mm/sec)
Dy2Fe16Ga1
Dy2Fe16Ga0.25Zr0.75
Dy2Fe16Ga0.5Zr0.5
Dy2Fe16Ga0.75Zr0.25
Dy2Fe16Zr1
Absorption(%)
280
240
200
160
HF(kOe)
4f
4e
6g4
6g2
12j8
12j2
12k8
12k2
-0.3
-0.2
-0.1
0.0
0.1
IS(mm/sec)
1.00.80.60.40.20.0
x, Dy2Fe16Ga1-xZrx
4f
4e
6g
12j
12k
• Paramagnetic DyFe3 phase was detected in the
Mössbauer spectra. The contribution of DyFe3
paramagnetic phase goes increasing with
increasing the Zr content and found to be 9% for
x = 1.00.
• Hyperfine field parameters decreases with due to
decrease in magnetic moment of Fe atom
• Isomer shift increases due to the unit cell
Mössbauer Studies contd…
Fig 18. RT Mössbauer spectra of Dy2Fe16Ga1-xZrx
Fig 19. RT Bhf and IS for Dy2Fe16Ga1-xZrx

25. Gd2Fe16Ga0.5TM0.5 (TM = Cr, Mn, Co, Ni, Cu, Zn)
Results and Discussion
Magnetic Atom Doped 2:17 compound
Part B

26. Structural Studies
Fig 20: XRD of Gd2Fe16Ga0.5TM0.5 (TM = Cr, Mn, Co, Ni, Cu,
Zn)
Fig 21:. Unit cell volume of Dy2Fe17-xCrx.
• Fe phase is reported for Ni and
Cu doping that causes the high
magnetization.
• The variation of unit cell volume
is observed because of the
variation in metallic radius of the
TM.
Intensity(a.u.)
706050403020
2θ (degree)
TM = 0.0
TM = Cr
TM = Mn
TM = Ni
TM = Co
TM = Cu
TM = Zn
Ga = 1.0
Fe
525
524
523
522
Volume(Å
3
)
76543210
TMGd2Fe17 Cr Mn NiCo Cu Zn Gd2Fe16Ga1
Cr = 128 pm Ni = 124 pm,
Mn = 127 pm Cu = 128 pm,
Fe = 126 pm Zn = 134 pm
Co = 125 pm Ga = 135 pm
( )
2
1
2
2
2
22
3
4
−






+
++
=
c
l
a
khkh
d hkl
V= a2
c sin60º

27. Magnetic Studies
• It is seen that 3d electrons in Cr, Mn is less
than that of Fe which lowers the
magnetization while 3d electrons of Co, Ni
and Cu are more greater than 3d electrons of
Fe which increases the magnetization of Fe
upon hybridization.
• Mn doped intermetallic has very low Ms of
its couples antiferromagnetically with Fe.
• Tc is higher for Co, Ni and Cu doped sample
because of the positive Fe-Fe exchange
interaction.
• The observed Tc for Cr, Mn, and Zn are still
better than the Tc of Gd2Fe17. This
75
70
65
60
Ms(emu/gm)
76543210
TM
580
570
560
550
540
530
520
Tc(K)
Gd2Fe17 Cr Mn NiCo Cu Zn Gd2Fe16Ga1
Ms
Tc
Fig 23: Bethe-Slater curve
Fig 22: Ms and Tc plot of Gd2Fe16Ga0.5TM0.5

28. MössbauerStudies
Fig 23: Gd2Fe16Ga0.5TM0.5 (TM = Cr, Mn, Co, Ni, Cu, Zn)
1050-5-10
Velocity (mm/sec)
Gd2Fe17
1050-5-10
Gd2Fe16Ga0.5Cr0.5
Gd2Fe16Ga0.5Mn0.5
Gd2Fe16Ga0.5Co0.5
Absorption(%)
Gd2Fe16Ga0.5Zn0.5
Gd2Fe16Ga0.5Cu0.5
Gd2Fe16Ga1
1050-5-10
Velocity (mm/sec)
Gd2Fe16Ga0.5Ni0.5
Absorption(%)
-60x10
-3
-40
-20
0
IS(mm/sec)
76543210
TM
252
250
248
246
244
HF(kOe)
Dy2Fe17 Cr Mn Co Ni Cu Zn Gd2Fe16Ga1
HF
IS
Fig 24: Weighted average HF and IS
Gd2Fe16Ga0.5TM0.5.
1. Weighted Bhf decreases for TM = Cr and Mn because of decrease in
magnetic moment and For TM = Co, Ni and Cu the Bhf increases because of
the increase in magnetic moment due to doping.
2. Variation in IS is due to the (i) volume effect (ii) change in net electron
density with TM doping (iii) screening of d-electron concentration upon
hybridization.

29. Conclusion
• XRD of Dy2Fe17-xZrx compounds observed pure phase up to x = 0.75 and
for Dy2Fe16Ga1-xZrx pure phase observed upto x = 0.25 after than some
additional phase of DyFe3 detected at higher concentration of Zr.
• In both case Zr atoms prefers to occupy 12j and 12k Fe sites.
• Increase in bond length helps to improve the curie temperature of
Dy2Fe17-xZrxand Dy2Fe16Ga1-xZrx.
• Substituting Fe atoms by Zr atoms, increasing Curie temperature faster
than substituting Zr for Ga.
• On increasing the concentration of Zr, magnetization value observed
monotonically decreasing.
• The decrease in magnetization in Dy2Fe16Ga1-xZrxis because of
predomination of positive effect on the magnetic moment over negative
effect caused by the magnetic dilution of non-magnetic substituents.
• The hyperfine field value decrease and Isomer shift increase with Zr
doping for both Dy2Fe17-xZrx and Dy2Fe16Ga1-xZrxdue to decrease in magnetic
moment of Fe atoms.

30. Conclusion contd…….
• XRD of Gd2Fe16Ga0.5TM0.5 ( TM = Cr, Mn, Co, Ni, Cu, Zn)
compounds observed but for TM = Ni, Cu additional α-Fe peak
was observed.
• The volume of unit cell depends on the metallic radius of doped
transition metal for Gd2Fe16Ga0.5TM0.5 (TM = Cr, Mn, Co, Ni, Cu,
Zn).
• In case of Gd2Fe16Ga0.5TM0.5(TM = Cr, Mn, Co, Ni, Cu, Zn) the
magnetization was less than that of Gd2Fe17 are reported except for
TM = Co, Ni and Cu.
• The weighted average hyperfine fields (HF) of Gd2Fe16Ga0.5TM0.5
(TM = Cr, Mn, Co, Ni, Cu, Zn) were increased or decreased
depending upon the type of TM metal. The weighted average HF
and IS showed the dependence of these parameters with the type
of doping TM atom.

31. REFERENCE
1. H.R. Kirchmayr “permanent mangets and hard mangetic materials” J. Phys. D. Appl. Phys.
29 PP. 2763-2778, 1996
2. K. J. Strnat, “Modern Permanent Magnets for application in Electron-technology,” J. Phys.
D. Appl. Phys. 76, 1990.
3. B. Cullity and C. Graham, “Introduction of Magnetic materials”, 2nd
edition, 2009.
4. S. trout, “Rare earth magnet industry in the USA current status and future trends”, Rare
earth Magnet workshop, Newark, 2002.
5. Arnold magnetic Technologies
6. K. J. Strnat, “chapter 2, Rare earth-cobalt permanent magnets,” in handbook of
Ferromagnetic materials, 4 PP. 131-209, 1988.
7. Xiao Qunfeng Thesis work ISBN: 90-5776-098-3.
8. K. J. Strnat, "Chapter 2 - Rare earth-cobalt permanent magnets," in Handbook of
Ferromagnetic Materials, vol. 4, 1988, p. 131–209.
9. K. R. Rao, H. Ehrenberg, G. Markandeyulu, U. Varadaraju, M. Venkatesan, K. Suresh, V.
Murthy, P. Schmidt and H. Fuess, "On the Structural and Magnetic Properties of R2Fe17—
x(A,T)x (R = Rare Earth; A = Al, Si, Ga; T = Transition Metal) Compounds," physica status
solidi (a), vol. 189, no. 2, p. 373–388, 2002.
10. J. X. Zhang, J.-x. Z.-h. Cheng, B.-g. Shen, B. Liang, J. v. Lier, I. Kleinschroth, W.-s. Zhan
and H. Kronmuller, "Magnetic properties of R2Fe17-xGaxC (R = Gd, Tb) compounds," J. of
Magn. and Magn. Mater., vol. 183, pp. 111-116, 1998.
11. I. Betancourt and H. Davies, "Influence of Zr and Nb dopant additions on the microstructure
and magnetic properties of nanocomposite RE2(Fe,Co)14B/α(Fe,Co) (RE = Nd–Pr) alloys," J.
Mag. Magn. Mater., vol. 261, no. 3, p. 328–336, 2003

32. Conferences and presentation attended
• MT-23 Continental Conference on July 14-19, 2013 Boston MA for
poster presentation.
• TN-SCORE annual conference on 10-11, June 2013 for poster
presentation.
• 2nd
Annual TN-SCORE Thrust 1 Retreat on 20-21 May 2013 for
poster presentation
• 25th Annual Student Research Forum at The University of Memphis
on April 1 2013 for poster presentation
• Poster presentation on 12th
Joint MMM/Intermag Conference on 14-
18 Jan 2013
• 2nd
Annual Memphis Research and Innovation Expo on 27
September 2012 at the University of Memphis.

33. Some other work done during my tenure in the UofM
1. Structural, magnetic and Mossbauer studies of and Dy2Fe16Ga1-xNbx (0 = 0, 0.2, 0.4,
0.6, 0.8, 1.00).
2. Synthesis and Magnetic Properties of SrAlxFe(12-x)-yCoyO19 (x = 0, 1, 2, 3, 4 and y=0,
0.5, 1.0, 1.5, 2.0) ferrites via simple auto-combusiton method.
3. Synthesis and characterization of SrFe12O19-CoFe2O4 core shell structure by
Autocombustion route.
4. Synthesis and Magnetic Properties of exchange-coupled SrFe12O19 - x Wt.%-
La0.7Sr0.3MnO3 nanocomposites via autocombusiton method.
5. Synthesis and Magnetic Properties of hard-soft SrFe12O19 -La1-xSrxMnO3 (x=0, 0.25,
0.5, 0.75, 1.00) nanocomposites via autocombusiton route.
6. Synthesis and Magnetic Properties of Sr1-yPryFe12-xCoxO19 (y = 0.1, 0.2, 0.3; x = 0,
0.25, 0.50, 1.00, 1.50) ferrites via simple-autocombustion route.
7. Photocatalytic properties of silver loaded titanium dioxide powders produced by

34. Acknowledgement
• Prof. Sanjay Mishra
• Prof. M. Shah Jahan
• Prof. Donald R. Franceschetti
• Dr. Syed Ali Sikanthar
• Staff of Department of Physics, U of M.
• Lijia Wang, Ganesh Pokharel, Armostrog Wilsion.
• R. Gnawali, D. Adhikari, S. Upreti, N. Shrestha and all
colleagues at Uof M.
• My beloved wife Gita Adhikari and son Sujit Dahal.

35. THANK
YOU !!!
Comments and suggestions…

36. • The general structure is 3RFe5-R+2Fe = R2Fe17
• The double layers are stacking on hexagonal structure.
• Three layers are stacking on the rhombohedral structure.
R2Fe17 structure