反強磁性交換結合媒体を用いた熱アシスト磁気記録の熱的安定性の検討 Investigation of Thermal Stability on Thermally Assisted Magnetic Recording Using Antiferromagnetic Exchange Coupled Medium 平成 1 年度三重大学大学院工学研究科博士前期課程物理工学専攻滝澤俊
1 1.1 1 1. 1 1.3 1.4 4 1.4.1 4 1.4. 4 1.4.3 5 1.5 6 8.1 8. 11..1 11..P-Type 1..3A-Type 15..4 17.3 18.3.1 18.3. K u V /kt (300 K) > 10 19.3.3 K u V /kt (300 K) > 60 3.3.4 5 6 3.1 6 3. 7 3..1 7 I
3.. 9 3..3 9 3..4 9 3.3 3 3.3.1Co/Ru/Co Ru 3 3.3.Co/Ru/Co 37 39 41 4 II
1.1 ( HD) HD HD 1970 1990 10 10 1990 10 100 1) 000 1. () 01 1.1 1.
Fig. 1.1. In-plane magnetic recording. Fig. 1.. Perpendicular magnetic recording. 1.3 ) 1.3(a) 1 1.3(b) 1.3(c) K u V / T K u V T
Fig. 1.3. Magnetic recording medium. (1) V () K u V T (1.1) 60 (3) H c H c = K u M s (1.) M s 3 V V (1.1) K u V T K u (1.) H c = K u M s
3 1.4 1.4.1 (Thermally assisted magnetic recording, TAMR) K u K u V / T V 1.4. 3) K u V / T 10 5-6 K u V / T V 1.4 (a) K u K u K u V / T 1.5(a) t 1.4(b) K u 1.5(b) K u K u M s 3) 3) Ir K u
4) Fig. 1.4. Temperature dependence of magnetic anisotropy energy constantfor ferromagnet 3).. Fig. 1.5. Time dependence of thermal stability for TAMR 3). 1.4.3 (Ferromagnetic exchange coupling, FC) 1 (Antiferromagnetic exchange coupling, AFC) AFC 1988 5) 1991 Parkin 6) 1.1 3d4d5d (TM)
RuRhIr AFC Co-Pt-Cr Co-Pt-Cr Ru Co 7) Girt Ar 8) Ar Desai Ar 9) Table 1.1. Antiferromagnetic exchange coupling energy via spacer-layer. 3d TM Ti V Cr Mn Fe Co Ni Cu (erg/cm ) No coupling 0.1 0.4 Ferromagnet Ferromagnet Ferromagnet 0.3 4d TM Zr Nb Mo Tc Ru Rh Pd Ag (erg/cm ) No coupling 0.0 0.1 5 1.6 No coupling No coupling 5d TM Hf Ta W Re Os Ir Pt Au (erg/cm ) No coupling 0.01 0.03 0.41 1.85 No coupling No coupling 1.5
( K ) K 3 Co/Ru/Co Co () 4
TAMR.1 TAMR.1 (a)(b) Parallel(P)-type (c) (d) Antiparallel(A)-type P-type (a)(b) w A-type (c) (d) w Fig..1. Two types of exchange-coupled films and behavior of the magnetization of the first layer under an external magnetic field. w.1 (b)(d) 1. (a) (b) (a) 180 (b) w 1 (a) 1 1 (a) 8
(b) w 1 1 K 1 K w Fig... (a) Exchange-coupling energy and (b) interface wall energy. P-type.3 (a)(b)(c) 3 M si t i H ci i H wi /M si t i w /M si t i (a)(b)(c) w (a)(b)(c) Fig..3. Calculated magnetization curves for P-type. 9
A-type.4 (a)(b)(c) 3 (a)(b)(c) w (a)(b)(c).3.4 A-type Fig..4. Calculated magnetization curves for A-type. P-type.5 (a) (Ferromagnetic exchange coupling, FC) FC 10 1 erg/cm A-type.5 (b) (AntiFerromagnetic exchange coupling, AFC) FC P-type AFC Ru Rh AFC 10 0 erg/cm Fig..5. Exchange-coupling energy for P-type and A-type. 10
...1 Fig..6. Energy barrier for single layer film..6 = H = 0 =, 0 = E 0 0 < < E 1 E 1 E 0 E E E = M s th cos + K u t sin (.1) E = M s thsin + K u t sin cos = sin (M s th + K u t cos) = 0 sin = 0, = 0, M s th + K u t cos = 0, cos = M sh K u (.) E 0 (.1) = E 0 = M s th E 1 (.1)(.) 11
E 1 = M s th cos + K u t sin = M s th cos + K u t (1- cos ) = M s th M H s + K u t(1 M H s ) = M th s + K u t M th s K u K u K u 4K u = M s th + K u t 4K u E E = E 1 E 0 = M s th 4K u + K u t M s th = K u t M s H +1 M sh 4K u K u = K u M sh + M sh K u K u = K u M sh = K u H K u K u M s (.3) H k = K u /M s E = K u H H k ( K ) ES T ES / T S T K K = ES T = K uts T 1 H H k H = 0 E E = K u t K K = K uts T..P-type P-type.3 (a).7 (a).3 (b)(c).7 (b) 1
Fig..7. Energy barrier for P-type films. (1) (.7 (a)) E E = (M s1 + M s t )H cos + (K u1 + K u t ) sin (.1) M s t M s1 + M s t (.4) K u t K u1 + K u t (.5) E (.3)(.4)(.5) E = (K u1 + K u t )1 (M s1 + M s t )H = (K u1 + K u t )1 (K u1 + K u t ) H c = (K u1 + K u t )/(M s1 + M s t ) H (K u1 + K u t ) M s1 + M s t E = (K u1 + K u t )1 H H c K K = ES T = (K u1 + K ut )S T H = 0 E E = K u t K K = (K u1 + K u t )S T 1 H H c 13
() (.7 (b)) E E = M s1 H cos + K u1 sin + cos = M s1 H cos + K u1 sin M s1 (.1) M s t M s1 (.6) H H M s1 (.7) K u t K u1 (.8) E (.3)(.6)(.7) (.8) M s1 H H M E = K u1 t 1 1 s1 t 1 M = K K u1 u1 1 s1 t 1 K u1 M s1 H k1 = K u1 /M s1 K H M E = K u1 1 s1 H k1 K = ES T = K u1 S 1 T H = 0 E E = K u1 1+ K K = K u1 S T H M s1 H k1 M s1 t 1 = K K u1 1+ u1 K u1 M s1 1+ K u1 14
..3A-type A-type P-type.4 (a).8 (a).4 (b)(c).8 (b) Fig..8. Energy barrier for A-type films. (1) (.8 (a)) E E = (M s1 M s t )H cos + (K u1 + K u t ) sin (.1) M s t M s1 M s t (.9) K u t K u1 + K u t (.10) H E = (K u1 + K u t )1 (K u1 + K u t ) M s1 M s t H c = (K u1 + K u t )/(M s1 M s t ) K E = (K u1 + K u t )1 H H c K = ES T = (K u1 + K ut )S T H = 0 E 1 H H c E = K u1 + K u t K 15
K = (K u1 + K u t )S T () (.8 (b)).7 (b) M s1 H H M E = K u1 t 1 1 s1 t 1 M = K K u1 u1 1 s1 t 1 K u1 M s1 H k1 = K u1 /M s1 H M E = K u1 1 s1 H k1 K K = ES T = K u1 S T H M 1 s1 H k1 H = 0 E E = K u1 1+ K K = K u1 S T M s1 t 1 = K K u1 1+ u1 K u1 M s1 1+ K u1 16
..4..1..3 P-TypeA-Type (1) K K = K u ts T 1 H H k (.11) H = 0 K = K uts T (.1) () P-Type K (a) H w1 + H w > H c H c1 K = (K u1 + K u t )S T 1 H H c (.13) H = 0 K = (K u1 + K u t )S T (.14) (b) H c H c1 > H w1 + H w H = 0 K = K u1 S T K = K u1 S T H M 1 s1 H k1 1+ K u1 (.16) (.15) (3) A-Type K (a) H w1 H w > H c1 + H c K = (K u1 + K u t )S T 1 H H c (.17) H = 0 K = (K u1 + K u t )S T (.18) (b) H c1 + H c > H w1 H w 17
H = 0 K = K u1 S T K = K u1 S T H M 1 s1 H k1 1+ K u1 (.0) (.19) (.13)(.0)P-Type A-Type K K u M s t K K K.3.3.4 P-type A-type A-type.1..3.1.9 Thermal gradient 8nm16 nm 7.5 nm Tbit/inch (Tbpsi)Thermal gradient Thermal gradient Field gradientdual gradient Field gradient Field gradient Dual gradient 18
Fig..9. Thermal gradient method using bit-patterned media. 300 K K u V /kt 10 A-type.10 1 M s K u 1 1.5 nm t 6.5 nm 450 K t = + t = 7.5 nm M s M s K u K u Fig..10. Parameter of A-type exchange coupled double layer for K u V /kt (300K) > 10. 300 K K u V /kt 60 K u1 = K u = 6.110 6 erg/cm 3.10.3. K u V /kt (300 K) > 10 A-type K (300 K).11 Thermal gradient H H = 0 19
H = 5 koe = 0 6.5 nm 7.5 nm K K K = 7.4 erg/cm.4(b) K = 7.4 erg/cm.4(a) K K.(a).(b) w w = 6. erg/cm.11 w /= 3.1 erg/cm K w /= 3.1 erg/cm K K Co/Ru/Co 5 erg/cm 6) 3.1 erg/cm Co Co Co-Pt-Cr 7) TAMR Fe-Pt-Cu Fig..11. Exchage coupling energy dependence of thermal stability factor for K u V /kt (300 K) > 10. 0
= 3.1 erg/cm K.1 K Fig..1. Temperature dependence of thermal stability factor for K u V /kt (300 K) > 10. A-type.13 = 0 1 1 1 7.4 erg/cm A-type 1.13 1 1 = 3.1 erg/cm 1 1 1 1 1
Fig..13. Exchage coupling energy dependence of switching field for K u V /kt (300 K) > 10. = 3.1 erg/cm.14 1 Fig..14. Temperature dependence of switching field for K u V /kt (300 K) > 10.
.3.3 K u V /kt (300 K) > 60 300 K K u V /kt 10 60 K (300 K).15 3.1 erg/cm.1 erg/cm K Fig..15. Exchage coupling energy dependence of thermal stability factor for K u V /kt (300 K) > 60. K.16.1 3
Fig..16. Temperature dependence of thermal stability factor for K u V /kt (300 K) > 60..17 1 =.1 erg/cm Fig..17. Exchage coupling energy dependence of switching field for K u V /kt (300 K) > 60. =.1 erg/cm.18 1 4
Fig..18. Temperature dependence of switching field for K u V /kt (300 K) > 60..3.4 K A-Type TAMR K A-Type K A-Type K u V /kt (300 K) > 10 = 3.1 erg/cm K u V /kt (300 K) > 60 =.1 erg/cm K Co-Pt-Cr 0.73erg/cm 7) TAMR Fe-Pt-Cu 5
Co/Ru/Co Co () 3.1 TAMR K 1 9) 1 1 Co Ru Co Co/Ru/Co Ru H s Co Co/Ru/Co Co 1 TAMR TAMR 500K H s 3.1 3 (a) 50W Co 1 (b) 100W Co 1 (c)(76mm6mm1mm) 10 ( 56) 10 10 Co 1 Co Co Ru 100 Co 60 Ru t Ru 08 3..1 6
Fig. 3.1. Sample structure. 3. 3..1 3. ( SBH- 306RDE) 3 ( DC-030F 800V/4A) 1kW ( RF-010A 13.56MHz 1kW)1 3 () ( D-950D)( CRYO-U 10PU) 1 Co 3 Ru 1 3 7
RF power supply matching box selecter motor chamber roughing valve substrate. non target mass flow 1. Co target 3. Ru target bypass valve rotary pump fore valve magnet main valve Ar N water cryo pump DC power supply 1 selecter DC power supply compresser Fig. 3.. Magnetron sputtering system. 3.1 10-4 Pa Ar Co Ru Co 1 Table 3.1.Sputtering conditions. 8
(1) Ru 100 () 1 Co 800 Co 60 (3) Ru (08) (4) Co 60 (5) Ru 100 3.. ( E-MD-S53A) 3..3 (Vibrating Sample Magnetometer, VSM VSM-5 )VSM ( ) 10mm10mm 3..4 H s Co/Ru/Co H s 9
Fig. 3.3. In-plane Mt-H loop of antiferromagnetic exchange coupled double layer. 1 M s t (> 0) H E M s H E = M s th cos M s th cos + cos (3.1) 1 1 Zeeman Zeeman 3 (3.1) 0 E E = M sthsin sin = 0 M s thsin sin = 0 M s thsin sin cos = 0 sin (M s th cos) = 0 sin = 0 (3.) M s th cos = 0 (3.3) 30
(3.) = 0 = (3.4) (3.3) cos = M s t H (3.5) cos 1 M s t H 1 1 M s t H 1 H M s t M s t (3.6) (3.5) H = /M s t (3.5) cos = 1 = 0 H (3.7) M s t (3.4) = 0 H = /M s t (3.5) cos = 1 = H M s t (3.8) (3.4) = (3.5) M s t cos = M s t M s t H (3.9) M s t cos 3.3 Mt H Mt Mt H H s =± M s t (3.10) ±M s t Mt H s = M s th s (3.11) 31
(3.11) (3.11) Co 60Å 10) Co 60Å(3.11) H s H s 3.3 3.3.1Co/Ru/Co Ru Ru 0850W 100W 3.4 3.5 3.6 Co/Ru/Co t Ru = 3Å 6) t Ru = 3Å AFC 50W 100W t Ru = 3Å AFC M-H loop 3.3 Co 1500 1000 1500 1000 M [emu/cm 3 ] 500 0-500 M [emu/cm 3 ] 500 0-500 -1000-1500 -10-5 0 5 10 H [koe] (a) -1000-1500 -15-10 -5 0 5 10 15 H [koe] (b) 3
1500 1500 1000 1000 M [emu/cm 3 ] 500 0 M [emu/cm 3 ] 500 0-500 -500-1000 -1500-10 -5 0 5 10 H [koe] 1500 (c) -1000-1500 -10-5 0 5 10 H [koe] (d) 1000 M [emu/cm 3 ] 500 0-500 -1000-1500 -6-4 - 0 4 6 H [koe] (e) Fig. 3.4. M-H loop on 50W etching Ru thickness (a) (b) 3(c) 4(d) 6(e) 8. 33
M [emu/cm 3 ] 1500 1000 500 0-500 M [emu/cm 3 ] 1500 1000 500 0-500 -1000-1500 -15-10 -5 0 5 10 15 H [koe] 1500 1000 (a) -1000-1500 -15-10 -5 0 5 10 15 H [koe] 1500 1000 (b) M [emu/cm 3 ] 500 0-500 M [emu/cm 3 ] 500 0-500 -1000-1500 -10-5 0 5 10 H [koe] (c) -1000-1500 -4-0 4 H [koe] (d) Fig. 3.5. M-H loop on 100W etching Ru thickness (a) (b) 3(c) 4(d) 6. 34
1500 1000 1500 1000 M [emu/cm 3 ] 500 0-500 M [emu/cm 3 ] 500 0-500 -1000-1500 -15-10 -5 0 5 10 15 H [koe] 1500 1000 (a) -1000-1500 -15-10 -5 0 5 10 15 H [koe] 1500 1000 (b) M [emu/cm 3 ] 500 0-500 M [emu/cm 3 ] 500 0-500 -1000-1500 -15-10 -5 0 5 10 15 H [koe] (c) -1000-1500 -10-5 0 5 10 H [koe] (d) 35
1500 1000 M [emu/cm 3 ] 500 0-500 -1000-1500 -8-4 0 4 8 H [koe] (e) Fig. 3.6. M-H loop on no etching Ru thickness (a) (b) 3(c) 4 (d) 6(e) 8. 3.4 3.5 3.6 H s Ru 3.7 (a)50w (b)100w (c) t Ru = 0 FC H s = 0 3.7(a)(b)(c) H s t Ru = 3Å H s t Ru = 6Å (a)50w (b)100w 50W H s [Co/Ru] 0.07erg/cm 11) 50W 4.8erg/cm Co 1 Co 1 1 36
Saturation field H s [koe] 18 16 14 1 10 8 6 4 0 0 4 6 8 Ru Thickness [Å] a) 50W Etching b) 100W Etching c) No etching fig. 3.7. Ru thickness dependence of saturation field. 3.3.Co/Ru/Co ( BH-800TC4) 533K 3.8 (a)50w (b)100w (c) 1 3 H s H 0 H s 533K H s TAMR 500K 493K H s Co Gd-Fe-Co H s 11) H s Co 1 37
Normalized saturation field H s /H 0 1. 1 0.8 0.6 0.4 0. 0 300 350 400 450 500 550 Annealing temperature [K] a) 50W etching b) 100W etching c) No etching Fig. 3.8. Annealing temperature dependence of normalized saturation field. 38
P-Type A- Type A-Type A-Type 1)A-Type K K K ) w K K 3)A-Type A-Type Ru Rh AFC AFC FC AFC AFC Co/Ru/Co Co 1 39
Ru H s TAMR 533K H s 4) Co 1 H s H s 5) Co 1 533K H s 40
41
1) HDD pp. 615-61007 ) S. H. Charap, P. Lu, and Y. He, "Thermal stability of recorded information at high densities," IEEE Trans. Magn., 33, pp. 978-983, 1997 3) MR004-64005 4) MR005-5006 5) M. N. Baibich,. M. Broto, A. Fert, F. Nguyen Van Dau, F. Petroff, P. Eitenne, G. Creuzet, A. Friederich, and. Chazelas, "Giant magnetoresistance of (001)Fe/(001)Cr magnetic superlattices," Phys. Rev. Lett., 61, pp. 47-475, 1988 6) S. S. P. Parkin, "Systematic variation of the strength and oscillation period of indirect magnetic exchange coupling through the 3d, 4d, and 5d transition metals," Phys. Rev. Lett., 67, pp. 3598-3601, 1991 7) A. Inomata, B. R. Acharya, E. N. Abarra, A. Ajan, D. Hasegawa, and I. Okamoto, "Advanced synthetic ferrimagnetic media,". Appl. Phys., 91, pp. 7671-7675, 00 8) E. Girt, and H.. Richter, "Antiferromagnetically coupled perpendicular recording media," IEEE Trans. Magn., 39, pp. 306-310, 003 9) M. Desai, A. Misra, and W. D. Doyle, "Effect of interface roughness on exchange coupling in synthetic antiferromagnetic multilayers," IEEE Trans. Magn., 41, pp. 3151-3153, 005 10) H. Wakabayashi, H. Notarys,. C. Suits and T. Suzuki, "Magnetic and magneto-optical properties of exchange coupled films of transition metals/tbfeco," Mat. Res. Soc. Symp. Proc., 150, pp. 95-101, 1989 11) [Co/Ru] 0 007 4