A phenomenological theory of the granular size effect on the giant magnetoresistance of granular films

作者：Wang, CZ; Guo, ZH; Rong, YH^*; Hsu, TY

来源：Journal of Magnetism and Magnetic Materials, 2004, 277(3): 273-280.

DOI：10.1016/j.jmmm.2003.10.033

• magnetic granular films
• giant magntoresistance
• log-normal distribution function
• effective medium theory
• spinasymmetric scattering factor

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 D-1(T) and D-2(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.

• 出版日期2004-6-11
• 单位上海交通大学