颗粒巨磁阻的唯象理论

A phenomenological Theory of Giant Magneto-Resistance in Magnetic Granular Alloys

文章用有效介质理论（ＥＭＴ）结合双通道模型的方法研究了巨磁阻效应与磁性颗粒浓度、尺寸的关系。样品由非磁性金属（Ａｇ）中嵌入磁性小颗粒（Ｃｏ）构成。分别考虑了浓度与颗粒尺寸的影响。首先颗粒粒径有一个尺寸分布，而在某一测量温度下颗粒具有临界阻塞直径，这导致形成两种对电导率有不同影响的颗粒：超顺磁颗粒和铁磁颗粒。其次考虑了有效界面散射随颗粒浓度的变化对巨磁阻造成的影响。理论计算结果与实验结果相吻合。

The authors combine effective medium theory(EMT) with the two-channel conducting model to study the magnetic granular concentration dependence of a giant magneto-resistance (GMR) in magnetic granular composites. The composite is composed of small magnetic granules (such as Co) embedded in an immiscible nonmagnetic metallic matrix(such as Ag). The influence of granule size and concentration respectively is considered. Firstly, granules have a distribution in size, resulting in super-paramagnetic (SPM) granules and ferromagnetic granules which have different contributions to conductance. Secondly, the effective surface scattering is changed with the changes of concentration. The calculated result of GMR is in agreement with the experimental data.