Improvement of chemical ordering and magnetization dynamics of Co-Fe-Al-Si Heusler alloy thin films by changing adjacent layers

We demonstrate an improvement of chemical ordering and magnetic properties of Co2FeAl0.5Si0.5 (CFAS) Heusler alloy thin films, as well as having investigated the correlation between these two, to elucidate the influence of different capping-layers and under-layers. The structural characterization reveals a variation in the surface roughness, grain size as well as in the chemical ordering for different samples. The static magnetometry measurements demonstrate a variation in the magnetic anisotropy behavior. A detailed characterization of the magnetization dynamics was performed using Brillouin Light Scattering (BLS) technique and the magnetic parameters were extracted using analytical modelling of the spin wave spectra. The origin of magnetic anisotropy is found to be correlated with the chemical order and the interfacial properties which can be effectively tailored by changing the adjacent layers. The Gilbert damping constants were extracted from the BLS peaks which also show a broad tunability with the chemical order. A Gilbert damping constant as low as about 0.002 has been found. The observed effects can primarily be attributed to the different melting points of the under-layers and thermal expansion stress between the adjacent layers and CFAS thin films.