high magnetic anisotropy materials - mint center · contents. 1. introduction 2. origin of magnetic...
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High Magnetic Anisotropy Materials
Takao Suzuki MINT Center
MINT Seminar (2/6/2015) 1
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Contents
1. Introduction 2. Origin of Magnetic Anisotropy3. High Magnetic Anisotropy Materials4. L10 FePt5. m-DO19 (Co-Ni)3Pt6. m-DO19 Fe3Pt7. Low Temperature Phase (LTP) MnBi8. Summary
MINT Seminar (2/6/2015) 2
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3
Dynamic Static
1 1,000 10,000Hk, Hc (Oe)
Sensor Data Storage Magnet
Ni3Fe, Fe3Al, Fe3NiMoa-CoFeSiB
K (erg/cc) 102~3 106 107~8
H
M
HC
Magnetic Materials
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a-TbFeCo, CoCrPt, FePt, NdFeB, SmFeN, SmCo5
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Hk 2K / Ms > Hc
Hk: Magnetic Anisotropy FieldK: Magnetic Anisotropy Constant
Ms: Saturation MagnetizationHc: Coercivity
TDK ( 1/12/2015) High Magnetic Anisotropy 4
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MaterialK
(MJ/m3)Ms
(MA/m)Hk(T)
Tc(K)
(BH)max(MGOe)
((K/M2)1/2)
SmCo5 17.2 0.9 38 1020 19 4.3Sm2Fe17N3 8.6 1 17 749 45 2.1
FePt 6.6 1.1 12 750 40 2.0CoPt 4.9 0.8 12 840 25 2.5
Nd2Fe14B 4.9 1.3 7.5 588 60 1.5Sm2Co17 4.2 1 8.4 838 28 1.9
MnBi 2 0.6 6.7 633 15 4.5Fe3Pt 2 1 4 640 15 4.0MnAl 1 0.7 2.9 653 10 1.2MnGa 1 0.3 6.7 500 10 3.6
Co 0.7 1.4 1 1400 - 0.2Alnico5 0.7 1.1 1.3 1210 5 0.7Fe50Ni50 0.6 1 1.2 - - 0.7
BaFe12O19 0.3 0.4 1.5 740 4 1.4MnSb 0.1 0.8 0.3 573 - 0.7
High Magnetic Anisotropy Materials
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Courtesy: Kronmuller and Goll
Browns Coercivity Paradox (Rev.Mod.Phys.1945)
MnBi
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Magnetic Anisotropy
2. Magnitude
K1 (Ni): 4 x 104 erg/cc (0.2 eV/atom)K1 (Fe): 5 x 105 erg/cc (2 eV/atom) Ku1 (Co): 5 x 106 erg/cc (20 eV/atom)K (Tb, Dy): order of 107-8erg/cc (0.1 1 meV/atom)
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1 kA/m= 1 emu/cm31 kA/m = 12.57 Oe
Magnetic Anisotropy
Magnetic anisotropy K = Ms x Hs = (1,400 emu/cc
x 6.5kOe) = 5 x 106 erg/cc
E.A.
E.A. E.A.
H.A.
H.A. H.A.
1. Example
MINT Seminar (2/6/2015) 8
Fe Ni Co
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9
1. Magnetic Anisotropy
Phenomenological expression
MINT Seminar (2/6/2015)
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Contents
1. Introduction 2. Origin of Magnetic Anisotropy3. High Magnetic Anisotropy Materials4. L10 FePt5. m-DO19 (CoNi)3Pt6. m-DO19 Fe3Pt7. Low Temperature Phase (LTP) MnBi8. Summary
MINT Seminar (2/6/2015) 10
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2. Origin of Magnetic Anisotropy
Magneto-crystalline Anisotropy (Intrinsic) Induced Magnetic Anisotropy (Extrinsic)
- Atomic Pair Model- Stress-induced Magnetic Anisotropy through
magneto-elastic coupling- Interface/surface Magnetic Anisotropy- Shape Magnetic Anisotropy- Exchange Biased Unidirectional Magnetic
Anisotropy
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Magneto-crystalline Anisotropy
Spin Angular Moment
Orbital Angular
MomentumLattice
Spin Angular Moment
Orbital Angular
MomentumLattice
3d elementsFe, Ni, Co
RE elementsTb, Dy, Nd
S CouplingCrystalline field
S L
Magnetic Anisotropy
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Rare Earth Intermetallic Compounds
High anisotropy due to theasymmetrical 4f shells that lead toa large spin-orbit coupling.
Nd3+Sm3+
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13
Fe
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K M(s)10 (1954, Zener)K M(s)4-8 (1958, Graham)
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YIG
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H.Callen and E.Callen (1957).
l : the order of polynomial function of S
Exp. Data by G.Rodrigue et al (1960).
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15
Ni
MINT Seminar (2/6/2015)
H.Callen and E.Callen (1957).
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16
h.c.p. Co
M.Takahashi and T.Suzuki; Japanese J. Apply.Phys.18, No6, 1071-1078 (1979).
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Yoshichika Otani, Hideki Miyajima and Soshin Chikazumi: Magnetocrystalline anisotropy in Nd-Fe-B magnet J.Appl.Phys. 61(8), 3436-3438 (1987). 17
Nd2Fe14B
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18
Gd
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Contents
1. Introduction 2. Origin of Magnetic Anisotropy3. High Magnetic Anisotropy Materials4. L10 FePt5. m-DO19 (CoNi)3Pt6. m-DO19 Fe3Pt7. Low Temperature Phase (LTP) MnBi8. Summary
MINT Seminar (2/6/2015) 19
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MaterialK
(MJ/m3)Ms
(MA/m)Hk(T)
Tc(K)
(BH)max(MGOe)
((K/M2)1/2)
SmCo5 17.2 0.9 38 1020 19 4.3Sm2Fe17N3 8.6 1 17 749 45 2.1
FePt 6.6 1.1 12 750 40 2.0CoPt 4.9 0.8 12 840 25 2.5
Nd2Fe14B 4.9 1.3 7.5 588 60 1.5Sm2Co17 4.2 1 8.4 838 28 1.9
MnBi 2 0.6 6.7 633 15 4.5Fe3Pt 2 1 4 640 15 4.0MnAl 1 0.7 2.9 653 10 1.2MnGa 1 0.3 6.7 500 10 3.6
Co 0.7 1.4 1 1400 - 0.2Alnico5 0.7 1.1 1.3 1210 5 0.7Fe50Ni50 0.6 1 1.2 - - 0.7
BaFe12O19 0.3 0.4 1.5 740 4 1.4MnSb 0.1 0.8 0.3 573 - 0.7
High Magnetic Anisotropy Materials
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High Magnetic Anisotropy Materials
0
10
20
30
40
50
60
70
80
K(MJ/m)x4
Hk(T)
(/M2 x10
22MINT Seminar (2/6/2015)
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Contents1. Introduction 2. Origin of Magnetic Anisotropy3. High Magnetic Anisotropy Materials4. L10 FePt5. m-DO19 (CoNi)3Pt6. m-DO19 Fe3Pt7. Low Temperature Phase (LTP) MnBi8. MnRh9. Summary
MINT Seminar (2/6/2015) 23
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High Magnetic Anisotropy Materials
0
10
20
30
40
50
60
70
80
K(MJ/m)x4
Hk(T)
(/M2 x10
24MINT Seminar (2/6/2015)
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25
Fe-Pt
Co-Pt
Ni-Pt
at% Pt
L10(fct)
0 20 40 60 80 Pt
Fe
Pt
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26
8 9 10
Number of valence electrons
Fe50Pt50 Co50Pt50 Ni50Pt50
S = 1
(Fe-Co)50Pt50(Fe-Ni)50Pt50(Co-Ni)50Pt50(Fe-Co-Ni)50Pt50
Theory(Sakuma)
7
Mn50Pt50
(Fe-Cr)50Pt50
0
2
4
6 3
norm
alized K
u a
t C
o50P
t 50
0
1
2
Ku (
10
7erg
/cc)
inc.dec.
Co
DO
S(1
/Ry/
f.u./s
pin)
+spin
-spin
30
20
10
0
10
20
30
Pt
EF
0 0.2 0.4 0.6 0.8
Energy(Ry)
valence electrons
Theory (Sakuma)
Density of Stateis determined by changingFermi-level.(band structure : Co50Pt50)
H.Kanazawa & T.Suzuki2001)
Magnetic Anisotropy of L1o Ordered Films
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Contents
1. Introduction 2. Origin of Magnetic Anisotropy3. High Magnetic Anisotropy Materials4. L10 FePt5. m-DO19 (CoNi)3Pt6. m-DO19 Fe3Pt7. Low Temperature Phase (LTP) MnBi8. Summary
MINT Seminar (2/6/2015) 27
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28
Co3Pt
Ni3Pt
Fe-Pt
Co-Pt
Ni-Pt
CoPtCoPt3
NiPt
FePtFePt3
at% Pt0 20 40 60 80 Pt
L12
m-DO19(Pmm2)
DO19
CoPt
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4.2
Co
Pt
2.6
Y. Yamada, T. Suzuki and N.Abarra: IEEE Trans.MAG 33 (1998).m-DO19 (Pmm2)
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Cross-section view of a Co3Pt film
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Dependence of Magnetic anisotropy on (c/a)
0
10
20
012345
1.615 1.620 1.625 1.6300.0
0.5
1.0
450
425400
25 150
200250 300
325
500450
400350
Lattice constant ratio, c/a
Co 3Pt
525500
475
375350
325
300
275
6K
u(1
0er
g/cc
)
(CoNi) 3Pt
440450 425
400
375
350
330325
Ni 3Pt
Substrate : Al2O3(001)Thickness : 500 +
G. LauhoffT. Suzuki, and A. Toporov, J. Appl. Phys. 100, 063909(2006)MINT Seminar (2/6/2015) 30
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DO19
Pmm2(m-DO19)
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Contents
1. Introduction 2. Origin of Magnetic Anisotropy3. High Magnetic Anisotropy Materials4. L10 FePt5. m-DO19 (CoNi)3Pt6. m-DO19 Fe3Pt7. Low Temperature Phase (LTP) MnBi8. Summary
MINT Seminar (2/6/2015) 32
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High Magnetic Anisotropy Materials
0
10
20
30
40
50
60
70
80
K(MJ/m)x4
Hk(T)
(/M2 x10
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Fe3Pt
Fe-Pt
Co-Pt
Ni-Pt
CoPtCoPt3
NiPt
FePtFePt3
at% Pt0 20 40 60 80 Pt
L12
m-DO19(Pmm2)
DO19
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Bulk Magnetic Property of Fe3Pt Ferromagnetic Tc = 430 K Ms (4.2 K) = 1538 (75 at%Fe) - ordered phase
1495 ( 72 at%Fe) - disordered phase2.13 ~ 2.17 B
= 1.0 x 10-4 emu/cc (ordered)1.5 x 10-4 emu/cc (disordered)
K : < 103 erg/cc (300 K) Very high volume magnetostriction =1.7 x 10-2 ( ordered) Invar Property 35MINT Seminar (2/6/2015)
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20 40 60 80 100
Cu-K
E-Beam EvaporationDeposition rate: 0.1A/s
Thickness: 500 Sub. Dep. Temp: 400 0C
Angle, 2 (deg.)
Inte
nsity
(a.u
.) Fe 3
P(00
1)
Fe3P
(002
)
Fe3P
(003
)
Fe3P
(111
)
Fe3P
(222
)
MgO
(002
)
MgO
(004
)
MgO
(111
)
MgO
(222
)
Fe3Pt/MgO(100)
Fe3Pt/MgO(111)
MgO(100)
Fe3Pt
MgO(111)
Fe3Pt
36MINT Seminar (2/6/2015)
X-ray diffraction of Fe3Pt films
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-100 0 100
18 20 22 24
18 21 24
20 30 40 50 60
Fe3Pt/MgO(111)In
tens
ity (a
.u.)
(111)
2.00 3.40
(deg) (deg)2
(220)
Ts-ambient
250
300
350
400
450
500
550
ambient
Fe3P
t(1
11)
MgO (111
)
X-ray
DET.
Sample
-scan
Inte
nsity
(a.u
.)In
tens
ity (a
.u.)
(deg.)
37MINT Seminar (2/6/2015)
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Magnetic Anisotropy of Fe3Pt alloy thin films
200 300 400 500 600
0
1
2
3
4
5
0
5
10
15
20
Substrate Temperature, Ts (oC)
|K1|
(106
erg/
cc)
K 2 (1
06er
g/cc
)
Disordered Ordered
K1
K2
K1 = 4106 erg/cc, K2 = 2107 erg/cc
Fe or PtDisordered
M.A.I.Nahid and T. Suzuki, J. Mag. Magn. Mat, 286, 315(2005)
PtFe
Ordered
Fe3Pt/MgO(100), Fe3Pt/MgO(111)
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-6 -4 -2 0 2 4 6
-5
0
5
-6 -4 -2 0 2 4 6
-5
0
5
E=K1(122232)+K2(1222+ 2232 + 3212)+.
Magnetic anisotropy constants of Fe3Pt/MgOK1= 4106 erg/cc
K2= 2107 erg/cc
Magnetic anisotropy energy in Cubic
is the easy axis, since those K1 and K2 fulfill the condition
K2 > 9/4K1
K2=9K1
K2=9/4K1
K1
K2
H(kOe)
M (1
0-3 e
mu)
Substrate : MgO(100)Deposition temperature : 400 Thickness : 500
0 15 30 45 60 75 901.2
1.4
1.6
1.8
angle,
Hc (k
Oe)
Fe3Pt
39Hiroaki Yamamoto and Takao Suzuki: Unexpectedly Large Magnetic Anisotropy of Fe3Pt Alloy Thin Films with Various Crystallographical Orientations IEEE Trans.Mag., 44, No.11, 2868 (2008).
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L vs. K1, K2 for Fe3Pt
Ts increase
Ts increase
2.66 2.67 2.680
5
10
15
20
25
0
1
2
3
4
5
K2 (
106 e
rg/c
c)
L ()
|K1|
(106
erg
/cc)
2.64 for bulk
L =22
22
+
ca
(L: between atoms in basal plan and neighbors above and below)
Fe
Pt
1% expansion
40MINT Seminar (2/6/2015)
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41MINT Seminar (2/6/2015)
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Contents
1. Introduction 2. Origin of Magnetic Anisotropy3. High Magnetic Anisotropy Materials4. L10 FePt5. m-DO19 (CoNi)3Pt6. m-DO19 Fe3Pt7. Low Temperature Phase (LTP) MnBi8. Summary
MINT Seminar (2/6/2015) 42
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High Magnetic Anisotropy Materials
0
10
20
30
40
50
60
70
80
K(MJ/m)x4
Hk(T)
(/M2 x10
43MINT Seminar (2/6/2015)
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MINT Seminar (2/6/2015) 44
MnBi
HTP & LTP : P63/mmc(a=4.29A, c=6.12A c/a=1.42)QHTP: P2221 (distorted P63/mmc)(a=4.34A, c=5.97A c/a=1.37
T.Chen and W.E.Stutius:IEEE Trans.MAG-10, 581-586 (1974).
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250K
300K400K
200K
150K4K
45THE UNIVERSITY OF ALABAMA MINT
Center for Materials for INformation Technology
out-of-planeSiO2 /{Bi(3.2nm)/Mn(2nm)} x 10 / Ru (c-axis oriented film)
LTP MnBi Thin Films
University of Alabama MMM (November 6, 2014) 45
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X (Bi) =3.2 nm, y(Mn)=2, N=10
MINT Seminar (2/6/2015) 46
3-1 Temperature dependence of magnetic anisotropy
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c-axis (c-axis oriented film)c-axis (non-oriented film)a-axis (non-oriented film)
bulk (after B. W. Roberts (1956))
c-axis (bulk)a-axis (bulk)
MINT Seminar (2/6/2015) 47
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MnBiCorrelation between K and Ms
MINT Seminar (2/6/2015) 48
T
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Contents
1. Introduction 2. Origin of Magnetic Anisotropy3. High Magnetic Anisotropy Materials4. L10 FePt5. m-DO19 (CoNi)3Pt6. m-DO19 Fe3Pt7. Low Temperature Phase (LTP) MnBi8. Summary
MINT Seminar (2/6/2015) 49
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New materials ?
Stabilization of meta-stable phases
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bct FeCo
MINT Center, U.Alabama ISAMMA Panel (July 2013( 51
Uniaxial anisotropy constant Ku for (a) c/a=1.25 and (b) c/a=1.15 asA function of Co content x. Open circles represent calculated with CPA (coherent potential approximation) and closed squares do with VCA (virtual potential approximation.
Y.Kota and A.Sakuma: J.Magn.Soc.Jpn. 37, (2013).
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Measured: C=3.607A, a=3.582A (c/a=1.007)
M.Kotsugi, C.Mimata: Magn.Jpn. 6, (2011).
MINT Center, U.Alabama 52ISAMMA Panel (July 2013(
L1o FeNi
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CoxC (x= 2 3) Particles
MINT Center, U.Alabama ISAMMA Panel (July 2013( 53
V.Harris et al.,J.phys.D,43,165993 (2010).
(BH)max = 20 kJ/m3
Slide Number 1ContentsSlide Number 3Slide Number 4High Magnetic Anisotropy Materials Slide Number 6Slide Number 7Magnetic Anisotropy Slide Number 9Contents2. Origin of Magnetic AnisotropyMagneto-crystalline AnisotropySlide Number 13YIGSlide Number 15h.c.p. CoYoshichika Otani, Hideki Miyajima and Soshin Chikazumi: Magnetocrystalline anisotropy in Nd-Fe-B magnet J.Appl.Phys. 61(8), 3436-3438 (1987).Slide Number 18ContentsHigh Magnetic Anisotropy Materials Slide Number 21High Magnetic Anisotropy Materials ContentsHigh Magnetic Anisotropy Materials Slide Number 25Slide Number 26ContentsSlide Number 28Slide Number 29 Dependence of Magnetic anisotropy on (c/a)Slide Number 31ContentsHigh Magnetic Anisotropy Materials Slide Number 34Slide Number 35Slide Number 36Slide Number 37Magnetic Anisotropy of Fe3Pt alloy thin filmsSlide Number 39L vs. K1, K2 for Fe3PtSlide Number 41ContentsHigh Magnetic Anisotropy Materials Slide Number 44Slide Number 45Slide Number 46Slide Number 47Slide Number 48ContentsNew materials ?bct FeCoL1o FeNiCoxC (x= 2 3) Particles