Critical Materials for Magnetism · 6 Antiferromagnetism and other magnetic order 7 Micromagnetism...
Transcript of Critical Materials for Magnetism · 6 Antiferromagnetism and other magnetic order 7 Micromagnetism...
Tokyo, 21xi 2011
J. M. D. Coey
Physics Department and CRANN, Trinity College Dublin 2, Ireland
www.tcd.ie/Physics/Magnetism
Critical Materials for MagnetismCritical Materials for Magnetism
1. Materials used for applications of magnetism
Permanent magnetsSoft magnetsMagnetic recording
2. Permanent magnets — filling the gap
3. Perpendicular magnetic media and memory
1 Introduction
2 Magnetostatics
3 Magnetism of the electron
4 The many-electron atom
5 Ferromagnetism
6 Antiferromagnetism and other magnetic order
7 Micromagnetism
8 Nanoscale magnetism
9 Magnetic resonance
10 Experimental methods
11 Magnetic materials
12 Soft magnets
13 Hard magnets
14 Spin electronics and magnetic recording
15 Other topics
Appendices, conversion tables.
612 pages. Available now. 20% discount for INTERMAG. Order direct for £40 + p&p
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Tokyo, 21xi 2011
Critical raw materials Critical raw materials –– EU reportEU report
* Platinum group metals
Germanium
Tantalum
1.1. Materials used for applications Materials used for applications of magnetismof magnetism
Tokyo, 21xi 2011
4 Be9.01
2 + 2s0
12Mg24.21
2 + 3s0
2 He4.00
10Ne20.18
24Cr52.003 + 3d3
312
19K38.21
1 + 4s0
11Na22.99
1 + 3s0
3 Li6.94
1 + 2s0
37Rb85.47
1 + 5s0
55Cs13.29
1 + 6s0
38Sr87.622 + 5s0
56Ba137.32 + 6s0
59Pr140.93 + 4f2
1 H1.00
5 B10.81
9 F19.00
17Cl35.45
35Br79.90
21Sc44.963 + 3d0
22Ti47.884 + 3d0
23V50.943 + 3d2
26Fe55.853 + 3d5
1043
27Co58.932 + 3d7
1390
28Ni58.692 + 3d8
629
29Cu63.552 + 3d9
30Zn65.392 + 3d10
31Ga69.723 + 3d10
14Si28.09
32Ge72.61
33As74.92
34Se78.96
6 C12.01
7 N14.01
15P30.97
16S32.07
18Ar39.95
39Y88.912 + 4d0
40Zr91.224 + 4d0
41Nb92.915 + 4d0
42Mo95.945 + 4d1
43Tc97.9
44Ru101.13 + 4d5
45Rh102.43 + 4d6
46Pd106.42 + 4d8
47Ag107.91 + 4d10
48Cd112.42 + 4d10
49In114.83 + 4d10
50Sn118.74 + 4d10
51Sb121.8
52Te127.6
53I126.9
57La138.93 + 4f0
72Hf178.54 + 5d0
73Ta180.95 + 5d0
74W183.86 + 5d0
75Re186.24 + 5d3
76Os190.23 + 5d5
77Ir192.24 + 5d5
78Pt195.12 + 5d8
79Au197.01 + 5d10
61Pm145
70Yb173.03 + 4f13
71Lu175.03 + 4f14
90Th232.04 + 5f0
91Pa231.05 + 5f0
92U238.04 + 5f2
87Fr223
88Ra226.02 + 7s0
89Ac227.03 + 5f0 62Sm
150.43 + 4f5
105
66Dy162.53 + 4f9
179 85
67Ho164.93 + 4f10
132 20
68Er167.33 + 4f11
85 20
58Ce140.14 + 4f013
Ferromagnet TC > 290K
Antiferromagnet with TN > 290K
8 O16.00
35
65Tb158.93 + 4f8
229 221
64Gd157.3
3 + 4f7292
63Eu152.02 + 4f7
90
60Nd144.23 + 4f3
19
66Dy162.53 + 4f9
179 85
Atomic symbolAtomic Number
Typical ionic changeAtomic weight
Antiferromagnetic TN(K) Ferromagnetic TC(K)
Antiferromagnet/Ferromagnet with TN/TC < 290 KMetal
Radioactive
Magnetic Periodic Table
80Hg200.62 + 5d10
93Np238.05 + 5f2
94Pu244
95Am243
96Cm247
97Bk247
98Cf251
99Es252
100Fm257
101Md258
102No259
103Lr260
36Kr83.80
54Xe83.80
81Tl204.43 + 5d10
82Pb207.24 + 5d10
83Bi209.0
84Po209
85At210
86Rn222
Nonmetal Diamagnet
Paramagnet
BOLD Magnetic atom
25Mn55.852 + 3d5
96
20Ca40.082 + 4s0
13Al26.983 + 2p6
69Tm168.93 + 4f12
56
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OSiAlFeMgCaKNaHOthers
Si4+ O2-
Al3+
Fe
Crustal abundances (top 9) All magnetic elements (log scale}
Cr
Mn
Fe
Co
Ni Ce
Pr
Nd
Sm
Eu
Gd
Tb
Dy
HoEr
Tm
Yb
-1
0
1
2
3
4
5
Cr Mn Fe Co Ni Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb3d elements 4f elements
PmLog
(abu
ndan
ce, p
pm)
Js (T) TC(°C)Fe 2.15 771
Co 1.81 1087
Ni 0.61 355
Iron is 40 x as abundant as all the other magnetic elements taken together.
Crustal abundances of magnetic elements
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HysteresisHysteresis
Any macroscopic magnet exhibiting remanence is in a thermodynamically-metastable state.
M (Am-1)
H (Am-
1)
Ms
Mr
Hd
working point
coercivityHc
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The demagnetizing fieldThe demagnetizing field
M BHN
S
∇B = 0
B = μ0(H + M)Stray field
Demagnetizing field
Hd ≈ -N M
demagnetizing factor 0 ≤N ≤ 1
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Magnetic materials for applications
Ni-Fe/Fe-Co (heads)
Fe-Si
Fe-Si (oriented)
Ni-Fe/Fe-Co
Amorphous
Others
Others
Alnico
Sm-CoNd-Fe-B
Hard ferrite
Co- γ Fe 2 O 3
(tapes, floppy discs)CrO2 (tapes)
Iron (tapes)
Co-Cr (hard discs)
Soft ferrite
Others
Iron
Soft Magnets
HardMagnets
MagneticRecording
Hard Magnets
Fe, Sr, Ba, Nd, Sm, Co, Dy, Zr
Soft Magnets
Fe, SI, Co, Ni, Zn, Mn
Magnetic Recording
Fe, Ni, Co, Ta, PtBreakdown of magnetic materials in 2000 - 30 B$
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Summary of magnetic properties of useful materials
Tc (°C)
Ms (MAm-1) K (kJm-3) λ (10-6)
SmCo5 847 0.86 17200 -
Nd2Fe14B
CoPt
FePt
315
567
477
1.28
0.81
1.14
4900
4800
1800
-
-
-
SrFe12O19 467 0.38 330 -
Fe94Si6 770 1.68 48 -7
Co35Fe65 940 1.95 20 -60
Ni80Fe20 570 0.83 -1 2
(MnZn)Fe2O4 300 0.50 -3 -5
(NiZn)Fe2O4 590 0.33 -7 -25
Y3Fe5O12 287 0.14 -2 -1
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The permanent magnet market (~$10B)The permanent magnet market (~$10B)
Sintered Nd-Fe-B
Bonded Ferrite
Tonnage production:
Ferrite; 1,000,000 Nd-Fe-B; 80,000
Spindle motor
Voice-coil actuator
Sintered Ferrite
Bonded Nd-Fe-B
Alnico; Fe,Co,Ni,AlSm-Co; Sm, Co, Fe,
Zr,Cu
SrFe12O19
Nd2Fe14B
Nd,Dy,Tb,Fe,Co,B
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The LimitsThe Limits
Curie temperature TC. Should be > 550 K for RT applications
Magnetization Ms. Should be as large as possible. Many applications depend on Ms
2
Energy product |BH|max Should be as large as possible for a permanent magnet |BH|max< ¼μ0Ms
2
Coercivity Hc . Should be 0 for soft magnets, > ½Ms for hard magnets.
Cost. As low as possible
Tokyo, 21xi 2011
The LimitsThe Limits
Curie temperature TC. Should be > 550 K for RT applications
Magnetization Ms. Should be as large as possible. Many applications depend on Ms
2
Energy product |BH|max Should be as large as possible for a permanent magnet |BH|max< ¼μ0Ms
2
Coercivity Hc . Should be 0 for soft magnets, > ½Ms for hard magnets.
Cost. As low as possible
Magnetic ordering temperature of > 2000 materials
αFe2O3 Fe Co
Magnetic ordering temperature (K)
Highest Néel temperature
Highest Curie temperature
Tokyo, 21xi 2011
The LimitsThe Limits
Curie temperature TC. Should be > 550 K for RT applications
Magnetization Ms. Should be as large as possible. Many applications depend on Ms
2
Energy product |BH|max Should be as large as possible for a permanent magnet |BH|max< ¼μ0Ms
2
Coercivity Hc . Should be 0 for soft magnets, Hc > ½Ms for hard magnets.
Cost. As low as possible
Slater-Pauling Curve
Slope -1m μB
Fe65Co35 Ms =1.95 MAm-1
Cr Mn Fe Co Ni Cu6 7 8 9 10 11
Valence electrons
Tokyo, 21xi 2011
The LimitsThe Limits
Curie temperature TC. Should be > 550 K for RT applications
Magnetization Ms. Should be as large as possible. Many applications depend on Ms
2
Energy product |BH|max Should be as large as possible for a permanent magnet |BH|max< ¼μ0Ms
2
Coercivity Hc . Should be 0 for soft magnets, > ½Ms for hard magnets.
Cost. As low as possible
Energy product doubled ≈every 12 years during the 20th century
Tokyo, 21xi 2011
The LimitsThe Limits
Curie temperature TC. Should be > 550 K for RT applications
Magnetization Ms. Should be as large as possible. Many applications depend on Ms
2
Energy product |BH|max Should be as large as possible for a permanent magnet |BH|max< ¼μ0Ms
2
Coercivity Hc . Should be 0 for soft magnets, > ½Ms for hard magnets.
Cost. As low as possible
The main achievement of technical magnetism in the 20th century was mastery of coercivity 1900: 103 < Hc < 105 A m-1
2000: 1 < Hc < 2 107 A m-1
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4 Be9.01
12Mg24.21
2 He4.00
10Ne20.18
24Cr52.00
19K38.21
11Na22.99
3 Li6.94
37Rb85.47
55Cs132.9
38Sr87.62
56Ba137.3
59Pr140.9
1 H1.00
5 B10.81
9 F19.00
17Cl35.45
35Br79.90
21Sc44.96
22Ti47.88
23V50.94
26Fe55.85
27Co58.93
28Ni58.69
29Cu63.55
30Zn65.39
31Ga69.72
14Si28.09
32Ge72.61
33As74.92
34Se78.96
6 C12.01
7 N14.01
15P30.97
16S32.07
18Ar39.95
39Y88.91
40Zr91.22
41Nb92.91
42Mo95.94
43Tc97.9
44Ru101.1
45Rh102.4
46Pd106.4
47Ag107.9
48Cd112.4
49In114.8
50Sn118.7
51Sb121.8
52Te127.6
53I126.9
72Hf178.5
73Ta180.9
74W183.8
75Re186.2
76Os190.2
77Ir192.2
79Au197.0
61Pm145
70Yb173.0
90Th232.0
91Pa231.0
87Fr223
88Ra226.0
89Ac227.0
62Sm150.4
105
66Dy162.5
179 85
67Ho164.9
132 20
68Er167.3
85 20
58Ce140.1
13
8 O16.00
35
65Tb158.9
229 221
64Gd157.3
63Eu152.0
90
66Dy162.5
179 85
Atomic symbolAtomic Number
Atomic weight
Antiferromagnetic TN(K) Ferromagnetic TC(K)
Cost Periodic Table
80Hg200.6
36Kr83.80
54Xe83.80
81Tl204.4
82Pb207.2
83Bi209.0
84Po209
85At210
86Rn222
Metal
Radioactive
Nonmetal
BOLD Magnetic atom
25Mn55.85
96
20Ca40.08
13Al26.98
69Tm168.9
56
312 96
36
78Pt195.1
1043 1390 629
60Nd144.2
19 292
< $10/kg$10 - 100/kg
$100 - 1000/kg$1000 - 10000/kg
>$10000/kg
92U238.0
93Np238.0
71Lu175.0
57La138.9
2. Permanent Magnets 2. Permanent Magnets -- Filling Filling the Gap the Gap
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The permanent magnet market (~$10B)The permanent magnet market (~$10B)
SrFe12O19
Nd2Fe14B
Ms = 0.38 MA m-1
K = 330 kJ m-3
TC = 740 K
|BH|max< 35 MJm-3
Cost ~ 5$ kg-1
Ms = 1.28 MA m-1
K = 4.9 kJ m-3
TC = 588 K
|BH|max< 400 MJm-3
K = sin2θ θ
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ChallengesChallenges
The 2 MA m-1 material. Find a usable soft material with M > 2 MAm-1
The megajoule magnet. Double |BH|MAX again to 1000 kJ m-3.
The rare-earth free/reduced replacement of Nd-Fe-B. Should be as large as possible. Many applications depend on Ms
2
The gap magnet. Find a new material intermediate between ferrite and RE magnets.
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Soft magnets ≈ 10 B$ a-1
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Targets in the gap
|BH|MAX TC Ms K Raw materials cost
kJm-3 K MAm-1 kJm-3 $/kg
A 100 > 550 570 400 10
B 150 > 550 690 600 20
C 200 > 550 800 800 30
κ = (K/μ0Ms2)1/2 > 1;
K > μ0Ms2
Hc < Ha = 2K1/Ms
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Properties of some uniaxial ferromagnets
MnAl MnBi Mn2Ga Y2Fe14B Fe16N2 Fe3C YCo5
Ms
(MA m-1)
0.60 0.58 0.47 1.10 1.92 1.09 0.85
K1
(MJ m-3)
1.7 0.90 2.35 1.1 1.0 0.45 6.5
TC (K) 650 628 >770 590 810 560 987
κ 1.95 1.46 2.35 0.85 0.43 0.55 2.7
Materials
cost ($ kg-1)
<10 < 20 > 100 < 30 < 10 < 10 <50
How do we find a suitable new material ?
Combinatorial Materials Science
|BH|max 50 kJ m-3
Yamaguchi et al (89)
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Magnetocrystalline anisotropyMagnetocrystalline anisotropy
Shape anisotropy is limited to Ksh = ¼ μ0Ms2(1- 3N ); it implies κ <½. A better source
is magnetocrystalline anisotropy, mainly due to spin-orbit coupling and the crystal-field interaction.
Ea = K1 sin2θ + . . . . .
The leading term in the crystal-field interaction is
Hcf = B20{3Jz
2 - J(J+1)} B20 = A2
0 θ2
K1cf ~ B2
0 J2. It varies as the electric field gradient x atomic quadrupole moment
Spin-orbit coupling is stronger for 4f than 3d atoms.Hence the use of rare-earth intermaetallics as permanent magnets.
3.3. Perpendicular magnetic media Perpendicular magnetic media and memory.and memory.
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Cost Cost -- the constraintthe constraint
For bulk permanent magnets, we must choose elements which are easily available and cheap. 10 g for everyone on earth requires a million moles of magnet.
This constraint does not apply for thin film devices. One mole is enough to provide everyone with a microchip containing a magnetic film a few nanometers thick.
Tokyo, 21xi 2011
4 Be9.01
12Mg24.21
2 He4.00
10Ne20.18
24Cr52.00
19K38.21
11Na22.99
3 Li6.94
37Rb85.47
55Cs132.9
38Sr87.62
56Ba137.3
59Pr140.9
1 H1.00
5 B10.81
9 F19.00
17Cl35.45
35Br79.90
21Sc44.96
22Ti47.88
23V50.94
26Fe55.85
27Co58.93
28Ni58.69
29Cu63.55
30Zn65.39
31Ga69.72
14Si28.09
32Ge72.61
33As74.92
34Se78.96
6 C12.01
7 N14.01
15P30.97
16S32.07
18Ar39.95
39Y88.91
40Zr91.22
41Nb92.91
42Mo95.94
43Tc97.9
44Ru101.1
45Rh102.4
46Pd106.4
47Ag107.9
48Cd112.4
49In114.8
50Sn118.7
51Sb121.8
52Te127.6
53I126.9
72Hf178.5
73Ta180.9
74W183.8
75Re186.2
76Os190.2
77Ir192.2
79Au197.0
61Pm145
70Yb173.0
90Th232.0
91Pa231.0
87Fr223
88Ra226.0
89Ac227.0
62Sm150.4
105
66Dy162.5
179 85
67Ho164.9
132 20
68Er167.3
85 20
58Ce140.1
13
8 O16.00
35
65Tb158.9
229 221
64Gd157.3
63Eu152.0
90
66Dy162.5
179 85
Atomic symbolAtomic Number
Atomic weight
Antiferromagnetic TN(K) Ferromagnetic TC(K)
Cost Periodic Table
80Hg200.6
36Kr83.80
54Xe83.80
81Tl204.4
82Pb207.2
83Bi209.0
84Po209
85At210
86Rn222
Metal
Radioactive
Nonmetal
BOLD Magnetic atom
25Mn55.85
96
20Ca40.08
13Al26.98
69Tm168.9
56
312 96
36
78Pt195.1
1043 1390 629
60Nd144.2
19 292
< $10/kg$10 - 100/kg
$100 - 1000/kg$1000 - 10000/kg
>$10000/kg
92U238.0
93Np238.0
71Lu175.0
57La138.9
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Af F1 Cu F2
AMR GMR TMR
1μm2
GMR
TMR
AMR
1 μm2
RAMAC 1955 40 Mb
~1010
bytes/year
HDD 2005 160 Gb
~1021
bytes/year
perpendicular
year caapcity platters size rpm
1955 40 Mb 50x2 24” 1200
2005 160 Gb 1 2.5” 18000
Tokyo, 21xi 2011
Perpendicular thin film media and memoryPerpendicular thin film media and memory
50 nm
Co-Cr-Pt-Ta-B
Next step – bit patterned mediaaf
I
planar magnetic tunnel junction (MTJ)
free
pinned
B
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Thin film media and memoryThin film media and memory
Tetragonal L10 structure
FePtFePdCoPtNiFe ?CoFe ?
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1.E-01
1.E+01
1.E+03
1.E+05
1.E+07
1.E+09
1.E+11
1E-05 0.001 0.1 10 1000 100000
1E+070Crustal abundance (ppm)
Ann
ual p
rodu
ctio
n (t)
rare earths
Production/abundanceProduction/abundance
1 E 05
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Abundance/costAbundance/cost
0.1
1
10
100
1000
10000
100000
0.001 0.1 10 1000 100000Price ($/mole)
Abundan
ce (
ppm
) 3d
4f
Fe
Mn
Co
NiCr
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Gambling
GREENGREED
Science is sane.Physicists have saved space,time,energyCan they save the world ?
Versus
4. Summary and conclusions4. Summary and conclusions
Tokyo, 21xi 2011
Summary Summary -- Where are the limits?Where are the limits?
Polarization μ0Ms 2.45 T improvement unlikely (bulk)
Curie Temperature 1380 K improvement unlikely
Anisotropy Field 40 Timprovement pointlessEnergy product (BH)MAX512 kJ m-3 depends on Ms,
Energy product (BH)max 475 kJ m-3 depends on loop shape
Tokyo, 21xi 2011
ConclusionsConclusions
The era of exponential improvement of energy product is over.Emergence of a new permanent magnet material superior to Nd2Fe14B is unlikely.Rare earths are overpriced; prices should fall as production increases, but Dy will remain problematic.Rare-earth free bulk magnets can be envisaged. Materials should be Fe or Mn based; >100 kJm-3 should be achievable, maybe 200 kJm-3
The challenge for two-phase hard/soft nanostructures is to align the hard nanoparticles. The megajoule magnet seems to out of reachGood prospects exist for new perpendicular thin films for magnetic recording or spin electronics.
Tokyo, 21xi 2011