Simulation of Magnetization Process in Antiferromagnetic Exchange-Coupled Films 19
1...1 1-1...1 1-2...1 1-2-1... 1 1-2-2 HDD...2 1-2-3 ( )...3 1-3 GMR... 4 1-4 ( )...5 1-5 SFMedia...5 1-6 (HAMR)...6 1-6-1... 6 1-6-2 (FC )... 6 1-6-3 (AFC 2 )... 7 1-7... 8 2...9 2-1-... 9 2-2...9 2-3...9 2-4 AFC... 10 2-5 σ W J...11 3...12 3-1...12
3-2...12 3-2-1... 12 3-2-2... 13 3-2-3... 13 3-2-4... 14 3-2-5... 15 3-2-6... 15 3-3...16 3-4 Co/TM... 16 4...18 4-1...18 4-2 Co/TM/Co... 18 4-3...20 4-4 3...21 4-5 (Co/TM 20 )... 22 4-6...23 4-7...25 5...26...27...28...29
1 1-1 (Hard Disk Drive, HDD) 1990 10 100, SFMedia(Synthetic Ferri Media) (Heat-Assisted Magnetic Recording, HAMR) 1-2 1-2-1 ( N S ) 1-1(a) ( N N S S 1-1(b) N S 1-1 -1-
1-2-2 HDD HDD ( 1-2 (a)) 1-2-3 ( 1-2 (b)) ( ) HDD 1-2 (a) (b) ( ) GMR Giant xmagneto Resistance GMR 0,1 GMR 1-3 1-2 (a) (b) -2-
1-2-3 ( ) 1-3(a) i i H 1 1-3(b) 1-3(c) H 2 H 2 i H 1 H 2 M H 2 = 4πM (1-1) H 2 M H 1 H 2 H 2 1-3 -3-
1-3 GMR 1) (MR ) TM % MR GMR HDD GMR 1988 Fe Cr Fe/Cr Co Cu Co(7.5 )/Cu(9.3 ) MR 80 ( 1-4, ) 1-4 (koe) MR ( ) Si/Fe(40 )/[Co( t Co )/Cu(9.3 )] 16 /Cu(919 ) 1-4 Co MR 2) GMR H ( H = 0 ) Fe Co TM(Cr Cu ) (AntiFerromagnetic exchange Coupling, AFC) ( 1-5(a) H ( 1-5(b) ) R ap R p R ap R p R ap R p MR R ap R p R p (1-2) 1-5 -4-
1-4 ( ) 1 V V V K u V k B T (1-3) K u k B T V (1-3) K u 1-2-3 H 2 H c = 2K u (1-4) M s M s K u V V K u H c 3 trilenma 1-5 SFMedia 3) SFMedia(Synthetic Ferri Media) 1-6(a) ( ) V (1-3) SFMedia TM AFC ( 1-6(b) ) AFC 2 3 V 3 AFC 2 ( ) 1-6 -5-
4),5), 6) 1-6 (HAMR) 1-6-1 HAMR H c ( K u ) H 2 H c (1-3) V V (1-3) V HAMR 1-6-2 (FC ) 1-6-1 1-7 (a) K u ( H c K u H c (1-3) 1-7 (b) K u K u ( H c ) K u ( H c ) T c K u ( H c ) T c (Ferromagnetic exchange Coupling, FC) 2 1-7 (a) K u (b) K uv / k BT -6-
1-6-3 (AFC 2 ) 1-6-2 2 H rev K u / M s M s K u H rev 1-6-2 AFC 2 1-7 AFC 2 M stotal M s1 M s2 M stotal M stotal = M s1 M s2 (1-5) ( T c ) T c M stotal 1-8 M stotal -7-
1-7 2 2 TM AFC GMR SFMedia HAMR TM AFC 1 GMR HAMR SFMedia 2 (FC AFC) (σ W J ) Co TM AFC (J AFC ) 3 4 Co/TM/Co AFC J AFC J AFC 5-8-
2 2-1- - 2-2 (Ferromagnetic exchange Coupling, FC) (AntiFerromagnetic exchange Coupling, AFC) 2 1 2 AFC 2 1 2 7), 8) 2-3 2 σ W J 2 2-1 FC 2-1(a) σ W σ W J 12 [erg] J 1, J 2 [erg] K 1, K 2 [erg/cm 3 ] 2-1(b) 180 J J 12 [erg] -3d (Rare Earth-3d Transition Metal, RE-TM) GdFeCo/GdFeCo TbFeCo/TbFeCo FC 2 GdFeCo/GdFeCo FC2 σ W 1 2erg/cm 2 TbFeCo/TbFeCo FC2 σ W 5 erg/cm 2 J 12 GdFeCo TbFeCo σ W J 12 Co/TM/Co J J 12-9-
2-1 (FC) 2-4 AFC Ru Rh TM AFC AFC J J J AFC Co 3d,4d,5d J AFC 2-1 J AFC TM t 1 J AFC J 1 Ru J 1 = 5erg/cm 2 ( t 1=3 ) Rh J 1 = 1.6 erg/cm 2 ( t 1=7.9 ) 9) 2-1 AFC -10-
10) 2-5 σ W J 2-2(a) GdFeCo/Rh/GdFeCo Rh t Ru FC AFC ( t Ru=8 10 ) FC ( t Ru=0 ) ( t Ru=0 ) J Rh( t Ru=8 10 ) J AFC AFC J 12 FC σ W t Ru =0 FC 180 J 2-2(b) AFC J ( J AFC ) 1 2 AFC FC σ W J 2-2 Rh -11-
3 3-1 3-2 3-2-1 2 3-1 (z ) Co1 (x,y ) z a Co 3-1 3-2 -12-
H app 3-2-2 3-2-6 i 3-2 x x,y x φ i z θ i 3-2-2 H(H x, H y, H z ) M(M x, M y, M z ) θ M H = M H cosθ = (M x H x + M y H y + M z H z ) (3-1) i M si H app x y z (M six, M siy, M siz ) (3-2) (H appx, 0,0) (3-3) H app x y z 0 E Z i a E Z i = am si H app = am s ix H app x (3-4) M six H app x M six = M si sin θ i cosφ i (3-5) H app x = H app (3-4) E Z i = am si H app sin θ i cosφ i (3-6) 3-2-3 ( ) i E K i ( ) K u i -13-
( ) E K i = a(k ui 2πM 2 s )sin 2 θ i (3-7) 3-2-4 2 θ A 2 A(1 cosθ) / a (3-8) i i i+1 i+1 θ i,i+1 cosθ i,i+1 i = i+1 = r i i+1 x y z (x i, y i, z i ) (x i+1, y i+1, z i+1 ) x i = r sinθ i cos φ i y i = rsin θ i sinφ i (3-9) z i = r cosθ i x i+1 = r sinθ i+1 cosφ i+1 y i+1 = rsin θ i+1 sinφ i+1 (3-10) z i+1 = r cosθ i+1 cosθ i,i+1 cosθ i,i+1 = x x + y y + z z i i+1 i i+1 i i+1 (3-11) r 2 (3-11) (3-9) (3-10) cosθ i,i+1 = r2 sinθ i cos φ i sin θ i+1 cosφ i+1 + r 2 sinθ i sin φ i sinθ i+1 sin φ i+1 + r 2 cosθ i cosθ i+1 r 2 = sinθ i cosφ i sinθ i+1 cosφ i+1 + sinθ i sin φ i sinθ i+1 sin φ i+1 + cosθ i cosθ i+1 = sinθ i sin θ i+1 (cosφ i cosφ i+1 + sin φ i sin φ i+1 ) + cosθ i cosθ i+1 = sinθ i sin θ i+1 cos(φ i φ i+1 ) + cosθ i cosθ i+1 (3-12) -14-
i i+1 E i,i+1 i i+1 A i,i+1 E i,i+1 = 2 A {1 sin θ sinθ cos(φ φ ) cosθ cosθ )} i,i+1 i i+1 i i+1 i i+1 (3-13) a 3-2-5 TM ( n n+1) 2 θ J J(1+ cosθ) (3-14) n n+1 2 θ n,n+1 3-2-4 cosθ n,n+1 = sinθ n sin θ n+1 cos(φ n φ n+1 )+ cosθ n cosθ n+1 (3-15) E AFC J AFC E AFC = J AFC {1+ sinθ n sin θ n+1 cos(φ n φ n+1 ) + cosθ n cosθ n+1 } (3-16) 3-2-6 2 E total 3-2-2 3-2-5 E Z i E K i E i,i+1 E AFC 2 n E total = E Z i + E Ki + E i,i+1 + E i,i+1 + E AFC (3-17) i=1 2n i=1 n 1 i=1 2 n 1 i=n+1 (3-17) E total θ i φ i i E total E total θ i = 0 (3-18) E total = 0 φ i -15-
(3-18) (3-19) 3-3 3-3 2 f ( x, y) = 0 g(x, y) = 0 (3-19) ( x 0, y 0 ) ( x 1, y 1 ) ( x 1, y 1 ( x 0, y 0 ) ( x 2, y 2 ) x 2 = x 1 f (x, y ) 1 1 f ( x 1, y 1 ) x (3-20) y 2 = y 1 g(x 1, y 1 ) g(x 1, y 1 ) y ( x 2, y 2 ) ( x 0, y 0 ) x k+1 = x k f (x k, y k ) f (x k, y k ) x y k+1 = y k g( x, y ) k k g( x k, y k ) y (3-21) ( x 0, y 0 ) 3-4 Co/TM Co/TM 3-3 4-4 (x,y ) 3-2-2 3-2-5 θ i 90-16-
3-3 -17-
4 4-1 1 Co Ru Rh TM Co/TM J AFC M-H J AFC 4-2 Co/TM/Co 4-1 Co/TM/Co M-H TM AFC H=0 TM Co H H H s Co J AFC J AFC Co Co M s t Co J AFC = M t H s Co s (4-1) 2 Co/TM 4-1 M-H Co 2m J AFC = mm t H s Co s (4-2) 2(2m 1) (4-1) (4-2) (4-2) H Co θ E E = 2mM s t Co H cosθ + (2m 1)J AFC cos2θ (4-3) 1 2 Co (4-3) θ 0 E θ E θ = 2mM st Co H sinθ 2(2m 1)J AFC sin 2θ = 0 mm s t Co H sin θ 2(2m 1)J AFC sinθ cosθ = 0 sin θ{mm s t Co H 2(2m 1)J AFC cosθ}= 0-18-
sin θ = 0 (4-4) mm s t Co H 2(2m 1)J AFC cosθ = 0 (4-5) (4-4) (4-5) θ = 0 θ = π (4-6) cosθ = mm s t Co H 2(2m 1)J AFC (4-7) (4-6) 4-1 M-H (4-7) (4-7) θ = 0 H = H s 1 = mm s t Co H s 2(2m 1)J AFC J AFC = mm s t Co H s 2(2m 1) (4-2) m = 1 (4-1) 4-1 Co/TM/Co -19-
11) 4-3 4-1 Co M s A 4-2 Co t 60 M s t Co = 20 M s = 886emu/cm 3 M s A A = A bulkco ( ) 2 (4-8) M sbulkco M s M s = 886emu/cm 3 A = 0.39 10 6 erg/cm (4-8) M A s bulkco bulkco Co J AFC Co/Ru/Co Co/Rh/Co 5 erg/cm 2, 1.6 erg/cm 2 (3-2) 4-4 4-1 4-2 Co ( ) 12) -20-
10) 4-4 3 ( ) K u Co H s K u = M (4πM H ) s s s (4-9) 2 4-2 t Co 60 4πM s H s (4-9) K u 0 t Co 60 4πM s H s K u t Co =20 4πM s - H s 4 kg K u 1.8 10 6 erg/cm 3 K u 3 4-3 Co/TM/Co t Co =20 M s = 886emu/cm 3 A = 0.39 10 6 erg/cm J AFC = 5erg/cm 2 K u = 1.8 10 6 erg/cm 3 4-3(a) H s 20 4-3(b) H s 80 3-3(a) (b) 90 4-3 (a) H = 0.2H s (b) H = 0.8H s -21-
4-5 (Co/TM 20 ) 4-4 Co/TM (a) (b) Co/TM 20 4-4 4-4 (a) H sim H app H sim H app J AFC =5 erg/cm 2 t Co 60 A=1 10-6 erg/cm H app =22.4 koe, H sim =38 koe J AFC =5 erg/cm 2 t Co 20 A=1 10-6 erg/cm H app =67 koe, H sim =77kOe J AFC =5 erg/cm 2 t Co 20 A=0.39 10-6 erg/cm H app =107 koe, H sim =152 koe H sim H app 4-4(a) 4-4(b) -22-
sim app J AFC =5 erg/cm 2 t Co 60 A=1 10-6 erg/cm sim =0.085 app = 0.064 H sim /H app, sim / app 4-2 t Co 20 (J AFC =5 erg/cm 2 M s =1422 emu/cm 3 A=1.0 10-6 erg/cm) H sim /H app 1.15 sim / app 1.05 1 t Co 60 H sim /H app 1.71 sim / app 1.32 J AFC A H sim /H app sim / app J AFC A 4-2 H sim /H app sim / app A M s H sim /H app sim / app 4-3 J AFC =5 erg/cm 2 t Co 60 M s A A M s H sim /H app, sim / app M s A 4-3 M s A H sim /H app sim / app ( ) 4-6 H s Co 4-5 Co Co 4-6 4-6 -23-
80 3-6(a) t Co t Co 20 60 4-6(b) (c) J AFC A J AFC A Co 4-5 -24-
4-6 (a) Co (b) (c) Co ( H=0.8H s ) 4-7 Co t Co J AFC A H sim /H app sim / app Co Co t Co J AFC A -25-
5 2 2 TM AFC GMR SFMedia HAMR (Co ) Ru Rh J M-H 2m J AFC = mm t H s Co s 2(2m 1) (5-1) M s t Co 1 H s (4-2) J AFC Co1 H s H sim χ χ sim H s H app χ χ app H sim / H app χ sim / χ app ( 4-2 ) 1 Co t J AFC Co A H sim / H app χ sim / χ app 2 H s J AFC t Co 3 Co Co Co t Co J AFC A Co J AFC -26-
-27-
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1) (2006) 2) RE-TM (2006) 3) 31 14pD-7,p.376,(2007) 4) [Co/Ru] 20 31 14pD-8,p.377,(2007) 5) ( ) -29-