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三维二维一维零维块状晶体各种薄膜纳米线,纳米管纳米颗粒, 纳米点低维磁性材料二维磁性薄膜一维纳米线零维纳米点以及纳米颗粒广泛应用于各个领域。Fe (K1 0)Ni (K1 0, K2 = 0K1 0, K2 = 0易轴 u = K1 sin 2 + K2 sin 4 + . . . (更高阶向以般可以忽略)4) K1 |K1|Energy surfaceEasy plane ( = 90o)3) K1 0, K2 0:u = |K1| sin 2 + |K2| sin 4 a aJSJS2 2x x2 2x xa aJSJSNaNaE EV VE Eexex2 2x x2 22 22 2x x2 22 2exexx xijij2 2ijij2 22 2ijij2 21 12 2ijij2 2exexj ji ij ji iijijexex2 22 23 3exexexexA AA Af fN Na aJSJSa aJSJSE Ea aconstantconstantJSJS) ).(1(12JS2JScoscos2JS2JSE ES SS S2J2JS SS SJ J2 2H H交换能的作用是让相邻的磁矩沿同一方向排列常数A用以量度交换作用的强弱H HMMZeemanfMm = M-m = -Mm = 0柱外: M = 0, B = 0H柱内: M = Mz, Bz 0 Hz 0 ( but |Hz| M) Hdemag = Hin 0 as D/L 0)(,sinsin2212222121cgsNMKKNMfssssmsd ds sH HMMN为退极化因子的差acca21cbacr1r11r11rraN1NN1r1N2222,sin退磁场大减小退磁场和外场磁畴 磁矩同向排列的区域畴壁 两个相邻磁畴在磁矩改变方向前的过渡区域 180畴壁厚膜中90o and 180o 畴壁1000100)(21nMMpzz/2往往在厚膜中产生BlochNelabbabaN4baabN4tmsNelBloch单畴晶体或多畴晶体且易轴平行于畴壁,当磁场沿难轴方向时,有磁矩的转动,而沿易轴则未必。HH)0()cos(sin2KMHKuHMKHHhHHKMHMMmMHKMHKuMHKukswk22sin0cos)sin2(coscossin2)sin(sin2h1m1h1m1难轴: = /2由磁畴扩大(b)及磁化矢量(c)引起的磁化过程,(a)是退磁状态下的磁畴分布(在下方的磁化曲线标明了对应的阶段)(a)(b)(c)HH可逆壁移可逆壁移不 可 逆 壁不 可 逆 壁移移转向磁化转向磁化abcOHs HBs磁畴壁完全消失在零场下,对于具有单轴各项异性的磁性粒子HzfefeMMKVEkTEt90/01/0210,2sinKV当测量时间弛豫时间(Mr = 0, Hc = 0)E kT ln(f0t)If t = 100 sec, then E 25 kTIf t = 10 years, then E 40 kT00.51024681012M/M0d (nm)7 x 107 erg/cc4.5 x 106 erg/cc1 sec10 yr1 sec10 yrM has double exponential dependence on K and V00.20.40.60.81-9 -6 -3 0369 12 15Hcr/H0log(t)KV/kBT = 200100502510 yrssuperparamagnetism前驱物前驱物反应物反应物固体产物固体产物 (膜或粉)(膜或粉)气相产物气相产物能量能量
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