Structural, static and dynamic magnetic properties of Co2MnGe thin films on a sapphire a-plane substrate

Magnetic properties of Co2MnGe thin films of different thicknesses (13, 34, 55, 83, 100, and 200 nm), grown by rf sputtering at 400 degrees C on single crystal sapphire substrates, were studied using vibrating sample magnetometry and conventional or microstrip line ferromagnetic resonance. 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 miscut angle of the Al2O3 substrate. The twofold in-plane anisotropy field H-u is almost temperature independent, in contrast with the fourfold field H-4 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 alpha value of 0.0065 for the 55-nm-thick film. (C) 2010 American Institute of Physics. [doi:10.1063/ 1.3475501]