In-Plane Isotropic High-Frequency Soft Magnetic Co-Sio2 Films

Abstract

Hcp-Co-SiO2 films with different thicknesses were fabricated by homogeneously distributing nanocrystalline Co particles with a size of 5~10 nm in the amorphous SiO2 matrix. The Co columnar crystals grow perpendicularly to the film and exhibit perpendicular magnetic anisotropy. The tilting angle (θ) of the magnetic moments to the vertical direction decreases to 7.5° as the film thickness increases to 1097 nm. The Co fraction reaches 0.64, leading to low coercivity of 30-35 Oe for magnetic indirect exchange coupling of closely packed Co nanocrystalline particles. Perpendicular anisotropy leads to a ripple-stripe domain with two orders of magnitude wider than the nanoparticle size. The natural resonance frequency of film is about 1.9 GHz, corresponding to low-anisotropy field. However, it increases to 18 GHz as in-plane magnetic bias field reaches 2400 Oe, exhibiting in-plane isotropy. This hcp-Co-SiO2 nanocrystalline film provides an opportunity for potential application of isotropic films in micro-inductance and electromagnetic devices.

Keywords: Cobalt nanocrystalline, in-plane isotropy, perpendicular magnetic anisotropy, soft magnetic properties, high frequency