Magnetic Transition and Structural Evolution in NiCo/Ag Multilayers

概要

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The structures and magnetic properties of Ni77Co23 (1.8 nm)/Ag ($t_{\text{Ag}}$ nm) multilayers, prepared by dc-magnetron sputtering, have been studied as a function of Ag layer thickness ($t_{\text{Ag}}$). The films progressively evolve from ferromagnetic to superparamagnetic with $t_{\text{Ag}}$ increasing from 1.0 to 3.6 nm. This magnetic transition versus $t_{\text{Ag}}$ is accompanied by a gradual structural evolution from layered multilayers to a granular system composed of NiCo giant granules. The sizes of giant superparamagnetic granules are approximately 40–80 and 100–140 nm for the samples with $t_{\text{Ag}}=3.0$ and 3.6 nm, respectively. Furthermore, the granules grow as metastable fcc NiCo phases with a lattice parameter of $0.4044 \pm 0.0002$ nm. The mechanisms responsible for the phenomena and the relationship between magnetization and structural evolution in the films are discussed.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2006-05-15