Structural, static and dynamic magnetic properties of CoMnGe thin films on a sapphire a-plane substrate

TL;DR

This study investigates the magnetic properties of CoMnGe thin films grown on sapphire substrates, revealing anisotropy behaviors, temperature effects, and damping characteristics relevant for magnetic applications.

Contribution

The paper provides a detailed analysis of in-plane magnetic anisotropies and damping in CoMnGe thin films, highlighting the influence of growth conditions and substrate miscut.

Findings

Fourfold anisotropy easy axis aligns with substrate c-axis.

Twofold anisotropy varies with growth conditions and substrate miscut.

Gilbert damping constant is approximately 0.0065 for 55 nm film.

Abstract

Magnetic properties of CoMnGe thin films of different thicknesses (13, 34, 55, 83, 100 and 200 nm), grown by RF sputtering at 400{\deg}C on single crystal sapphire substrates, were studied using vibrating sample magnetometry (VSM) and conventional or micro-strip line (MS) ferromagnetic resonance (FMR). Their behavior is described assuming a magnetic energy density showing twofold and fourfold in-plane anisotropies with some misalignment between their principal directions. For all the samples, the easy axis of the fourfold anisotropy is parallel to the c-axis of the substrate while the direction of the twofold anisotropy easy axis varies from sample to sample and seems to be strongly influenced by the growth conditions. Its direction is most probably monitored by the slight unavoidable angle of miscut the Al2O3 substrate. The twofold in-plane anisotropy field is almost temperature independent, in contrast with the fourfold field which is a decreasing function of the temperature. Finally, we study the frequency dependence of the observed line-width of the resonant mode and we conclude to a typical Gilbert damping constant of 0.0065 for the 55-nm-thick film.