High Magnetic Anisotropy Materials - MINT Center · Contents. 1. Introduction 2. Origin of Magnetic...

High Magnetic Anisotropy Materials

Takao Suzuki MINT Center

MINT Seminar (2/6/2015) 1

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


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


a-TbFeCo, CoCrPt, FePt, NdFeB, SmFeN, SmCo5

Hk 2K / Ms > Hc

Hk: Magnetic Anisotropy FieldK: Magnetic Anisotropy Constant

Ms: Saturation MagnetizationHc: Coercivity

TDK ( 1/12/2015) High Magnetic Anisotropy 4

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



Courtesy: Kronmuller and Goll

Browns Coercivity Paradox (Rev.Mod.Phys.1945)

MnBi

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)

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


Fe Ni Co

9

1. Magnetic Anisotropy

Phenomenological expression

MINT Seminar (2/6/2015)

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


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

11MINT Seminar (2/6/2015)

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


Rare Earth Intermetallic Compounds

High anisotropy due to theasymmetrical 4f shells that lead toa large spin-orbit coupling.

Nd3+Sm3+

13

Fe


K M(s)10 (1954, Zener)K M(s)4-8 (1958, Graham)

YIG


H.Callen and E.Callen (1957).

l : the order of polynomial function of S

Exp. Data by G.Rodrigue et al (1960).

15

Ni


H.Callen and E.Callen (1957).

16

h.c.p. Co

M.Takahashi and T.Suzuki; Japanese J. Apply.Phys.18, No6, 1071-1078 (1979).


Yoshichika Otani, Hideki Miyajima and Soshin Chikazumi: Magnetocrystalline anisotropy in Nd-Fe-B magnet J.Appl.Phys. 61(8), 3436-3438 (1987). 17

Nd2Fe14B


18

Gd


Contents



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




0

10

20

30

40

50

60

70

80

K(MJ/m)x4

Hk(T)

(/M2 x10


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



0

10

20

30

40

50

60

70

80

K(MJ/m)x4

Hk(T)

(/M2 x10


25

Fe-Pt

Co-Pt

Ni-Pt

at% Pt

L10(fct)

0 20 40 60 80 Pt

Fe

Pt


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


Contents



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


29

4.2

Co

Pt

2.6

Y. Yamada, T. Suzuki and N.Abarra: IEEE Trans.MAG 33 (1998).m-DO19 (Pmm2)


Cross-section view of a Co3Pt film

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

DO19

Pmm2(m-DO19)


Contents




0

10

20

30

40

50

60

70

80

K(MJ/m)x4

Hk(T)

(/M2 x10


34

Fe3Pt

Fe-Pt

Co-Pt

Ni-Pt

CoPtCoPt3

NiPt

FePtFePt3

at% Pt0 20 40 60 80 Pt

L12

m-DO19(Pmm2)

DO19


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)

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


X-ray diffraction of Fe3Pt films

-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.)


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)


-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).


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


Contents




0

10

20

30

40

50

60

70

80

K(MJ/m)x4

Hk(T)

(/M2 x10



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).

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

X (Bi) =3.2 nm, y(Mn)=2, N=10


3-1 Temperature dependence of magnetic anisotropy

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)


MnBiCorrelation between K and Ms


T

Contents



New materials ?

Stabilization of meta-stable phases

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).

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

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

High Magnetic Anisotropy Materials - MINT Center · Contents. 1. Introduction 2. Origin of Magnetic...

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