Spin-Wave Spectroscopy and Magnetostructural Studies of Co Nanogranular Composites

Abstract

Nanogranular Co–SiO2, and Co–CaF2 films are investigated using ferromagnetic resonance and magnetic measurements. The spectrum of standing spin-wave has been registered in the perpendicular experiment configuration for all types of films with the magnetic granules content above 52 vol.%. The dependences of resonance fields Hr of spin modes on the mode number squared Hr(n 2 ) are non-linear. Such behavior is supposed to be the result of the fluctuations of magnetic parameters (the magnetization and the ferromagnetic exchange coupling) in nanocomposite films. A comparison between the magnetic properties of Co–SiO2 granular films and Co–CaF2 films is carried out. The surface anisotropy value Ks of Co–SiO2 films is evaluated from the surface resonance modes of spin-wave resonance spectra as 3.5 × 10−4 < Ks < 7 × 10−4 J/m2 . The magnetic anisotropy of Co100−x(SiO2)x, Co100−x(CaF2)x films (34 < x < 74) is investigated. The surface magnetic anisotropy of granules ks and the surface magnetic anisotropy of films Ks are determined. It is found that surface anisotropy of granules is predominant.