Magnetic properties of Fe-Ag granular alloys

摘要

A discontinuous Fe/Ag multilayer and a granular alloy, both with the overall nominal composition of Fe_(10)Ag_(90), were studied by bulk magnetization and Moessbauer spectroscopy measurements. The super-paramagnetic blocking temperatures, as measured by the low-field susceptibility, agree quite well but the external-field dependence of the magnetization shows large difference for the two samples at all temperatures and the grain sizes obtained from a Langevin fit to the bulk magnetization differ in almost a factor of two. The discrepancy is attributed to the different directions of anisotropy in the samples, as observed by Mossbauer measurements as well as by comparison of the magnetizations measured in parallel and perpendicular applied fields. Similar grain size is obtained for the two samples by both techniques when a simple large-field approximation (M(H)～M(∞)(1 -kT/μH)) is applied in the calculations.