The effect of the size distribution on the giant magnetoresistance in magnetic granular films

Abstract

PACS 75.47.De, 75.50.Tt In the present paper, assuming that there is a size distribution described by the log-normal function for the spherical granules in granular films, 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 multi-domain granules. Accordingly, magnetic granules can be divided into three categories: superparamagnetic, single-domain ferromagnetic and multi-domain ferromagnetic granules. In view of various contributions to the giant magnetoresistance (GMR) effect, the three kinds of granules are separated into two categories: first ferromagnetic granules (F 1 , consisting of singledomain ferromagnetic granules), which play a key role in the GMR effect; and second ferromagnetic granules (F 2 , including superparamagnetic and multi-domain granules), which play a secondary role in the GMR effect. We combine the effective medium theory with the two-channel conducting model to study the GMR effect of granular films in detail. As a result, our calculated results are qualitatively in agreement with experimental data, showing that the theoretical method is essentially applicable for magnetic granular composites.

Synthesis and characterization of nanocrystalline zinc substituted nickel ferrites

“…The average particle size is seen to decrease with increase in Zn concentration. The decrease in particle size with substitution of zinc ions may be due to the high-energy barrier of NiFe 2 O 4 than that of ZnFe 2 O 4 [13,14]. The observed particle size from TEM is in good agreement with XRD results.…”

Thermionic Vacuum Discharges for Thin Film Depositions

“…As given in the literature, the domain diameters distribution when they are considered spheres, is given by [55].…”