There are mainly two ways of theoretic study on gmr in magnetic granular alloys . one is to extended the quantum or quasi - classical treatments of gmr in multilayers to the one in magnetic granular systems . the other is a phenomenological method which adopes effective medium approxiation ( ema ) and two - channel model directly 颗粒复合膜中巨磁阻效应理论研究主要有两条途径：一条是将多层膜中巨磁阻效应的量子方法和半经典方法推广到颗粒复合体系，另一条是直接利用有效介质理论和双通道模型的唯象方法。
