长程相互作用自旋系统中磁各向异性势垒的增强
Enhancement of magnetic anisotropy barrier in long range interacting spin systems
摘要：
磁性材料通常以各向异性能垒为特征，各向异性能垒决定了磁化衰减的时间尺度，从而决定了样品的磁稳定性。在这里，我们提出了一个统一的描述，其中包括相干旋转和成核，在一般的各向异性自旋系统的磁化衰减。特别是，我们表明，在存在的长程交换相互作用，各向异性能垒增长的体积的粒子上的各向异性，而它的增长速度甚至比体积交换各向异性，与各向异性能垒成正比的$V^{2-α/d}$，其中$V$是粒子体积，$α\leq d $是相互作用的范围和$d$是嵌入维数。这些结果表明，各向异性能垒w.r.t.短程情况，其中对于大颗粒尺寸或大颗粒纵横比，各向异性能垒随着颗粒横截面积而增长。
英文摘要：
Magnetic materials are usually characterized by anisotropy energy barriers which dictate the time scale of the magnetization decay and consequently the magnetic stability of the sample. Here we present a unified description, which includes coherent rotation and nucleation, for the magnetization decay in generic anisotropic spin systems. In particular, we show that, in presence of long range exchange interaction, the anisotropy energy barrier grows as the volume of the particle for on site anisotropy, while it grows even faster than the volume for exchange anisotropy, with an anisotropy energy barrier proportional to $V^{2-α/d}$, where $V$ is the particle volume, $α\leq d $ is the range of interaction and $d$ is the embedding dimension. These results shows a relevant enhancement of the anisotropy energy barrier w.r.t. the short range case, where the anisotropy energy barrier grows as the particle cross sectional area for large particle size or large particle aspect ratio.
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