Kramers's rate theory, broken symmetries, and magnetization reversal
Kramers's rate theory, broken symmetries, and magnetization reversal
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克莱默斯速率理论、破缺对称性和磁化反转
DOI：
10.1063/1.358279
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发表时间：
1994
影响因子：
3.2
通讯作者：
H. Braun
中科院分区：
文献类型：
--
作者：
H. Braun
对小颗粒热致磁化反转理论进行了综述。本文首先讨论了均匀磁化反转的传统Neel-Brown理论及其由Kramers速率理论导出的结果。然而，对于足够长的粒子，非均匀能垒（“核”）具有比均匀能垒更低的能量，因此产生更低的矫顽力。当原子核破坏了易磁化轴周围的旋转对称性时，这种磁化率降低也会发生在消失的难磁化轴各向异性上。计算了均匀和非均匀障碍的Arrhenius因子的前因子。
The theory of thermally induced magnetization reversal in small particles is reviewed. The conventional Neel–Brown theory for uniform magnetization reversal and its derivation from Kramers’s rate theory are first discussed. For sufficiently elongated particles, however, a nonuniform energy barrier (‘‘nucleus’’) has lower energy than the uniform barrier and thus yields a lower coercivity. This coercivity reduction is shown to occur also for vanishing hard‐axis anisotropy when the nucleus breaks the rotational symmetry around the easy axis. The prefactor of the Arrhenius factor is calculated for uniform and nonuniform barriers.