非磁性半导体异常磁电阻效应的有效介质理论

Extraordinary magnetoresistance in nonmagnetic semiconductors:The effective-medium approximation

有效介质理论自洽方程被用来研究非磁性半导体材料的异常磁电阻效应.通过建立两组分无序电导网络,同时引入组分的霍尔效应,计算了体系的有效电导张量随磁场和组分浓度的变化关系.结果表明,当两种组分具有不同类型的载流子时,体系中各组分零场电阻的差异将导致在垂直磁场和平行磁场方向上产生异常的磁电阻效应.这些宏观的磁电阻效应来源于体系中的非均匀性,并与组分的几何逾渗结构具有明显的关联.

The self-consistent effective-medium approximation is used to study the extraordinary magnetoresistance effect observed in nonmagnetic semiconductors.The inhomogeneous materials are treated as a three-dimensional resistor network of binary disorder,where the receptivity of each component is a tensor describing both the zero-field resistance and the Hall effect.The effective conductivity tensor of the total system is calculated with applied magnetic field.The resulting transversal magnetoresistance,longitudinal magnetoresistance and effective Hall coefficient are shown for different component concentrations and magnetic fields.When the components have two different types of charge carriers,and the mismatch between the zero-resistivity is enlarged,the macroscopic magnetoresisance exhibits complex behaviors which are related closely with the formation of the percolation structure in the inhomogeneous system.