A phenomenological theory of the granular size effect on the giant magnetoresistance of granular films
A phenomenological theory of the granular size effect on the giant magnetoresistance of granular films
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DOI：
10.1016/j.jmmm.2003.10.033
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发表时间：
2004-06
影响因子：
2.7
通讯作者：
Changzheng Wang;Zhenghong Guo;Y. Rong;T. Hsu
中科院分区：
文献类型：
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作者：
Changzheng Wang;Zhenghong Guo;Y. Rong;T. Hsu
根据颗粒膜中磁性颗粒尺寸分布的存在，磁性颗粒可分为三类：超顺磁颗粒、单畴铁磁颗粒和多畴铁磁颗粒。本文分别以临界尺寸D1(T)和D2(T)作为不同温度下区分单畴铁磁颗粒、超顺磁性颗粒和多畴颗粒的唯象参数，并利用描述磁性颗粒尺寸分布的对数正态分布函数，结合有效介质理论和双通道导电模型，研究了三种磁性颗粒对巨磁阻（GMR）的不同影响。以Co-Ag颗粒薄膜为例，只有当单畴铁磁颗粒具有较大的自旋不对称散射因子作为GMR权重时，计算结果与报道的各种实验定性一致，由此表明单畴铁磁颗粒在GMR中发挥着关键作用。
Based on the existence of size distribution of magnetic granules in granular films, the magnetic granules can be divided into three categories: superparamagnetic, single domain ferromagnetic and multidomain ferromagnetic granules. In the present paper we take respectively the critical sizes D1(T) and D2(T) as phenomenological parameters at different temperatures distinguishing single domain ferromagnetic granules from superparamagnetic granules and from multidomain granules and use the log-normal distribution function describing the size distribution of magnetic granules to investigate the different effects of three kinds of magnetic granules on giant magnetoresistance (GMR) by combining effective medium theory with a two-channel conducting model. In the calculation of Co–Ag granular films as an example, only when single domain ferromagnetic granules possess larger spin-asymmetric scattering factor as weight with GMR, the calculated results are qualitatively in agreement with the various experiments reported, from which it indicates that single domain ferromagnetic granules play a key role in GMR.