High-frequency magnetic properties of [FeCo/FeCo-SiO2]n multilayered films deposited on flexible substrate

Abstract

A series of 120 nm [FeCo/FeCo-SiO2]n multilayer thin films with different FeCo layer thicknesses (T = 10–40 nm) and fixed FeCo-SiO2 layer thickness (20 nm) were deposited on flexible substrate (Mylar) by controlling the sputtering time under applied magnetic field. The magnetic properties of the multilayer thin films were investigated. The experimental results showed that the multilayer thin films had obvious in-plane uniaxial magnetic anisotropy, which can be adjusted in a broad range by changing the thickness of FeCo layer. In addition, good soft magnetic performance was obtained. The coercivity in the easy axis Hce of the multilayer films with the T = 10 nm, 20 nm, 30 nm, and 40 nm was 5 Oe, 25 Oe, 10 Oe, and 8 Oe, respectively. In frequency-dependent permeability spectra measurement, two resonance peaks of complex permeability spectrum were observed, especially for T = 20 nm, which can be attributed to the complicated magnetic structure of FeCo and FeCo-SiO2 layer. By introducing multilayers with different effect anisotropy field, one can broaden the absorption peak while maintaining the high permeability, which would open the way for their potential applications as wide-band microwave absorber.