Gilbert Damping Constant of Quaternary Co2MnAl1−x Sn x Heusler Alloy Thin Films

Polycrystalline quaternary Co2MnAl1−x Sn x films with x=0.25, 0.5, 0.75, 1 were prepared at room temperature using magnetron sputtering technique on SiO2 substrates and post-annealed at various temperatures. We investigated the crystal structures, magnetic properties, and magnetic damping constants (α) of the prepared films. Out-of-plane angular dependences of the resonance field and the linewidth of the ferromagnetic resonance spectra were measured and analyzed using the Landau–Lifshitz–Gilbert equation to determine the magnetic properties and damping constant. Co2MnAl0.75Sn0.25 and Co2MnSn films had A2 ordered crystal structure while Co2MnAl0.25Sn0.75 and Co2MnAl0.5Sn0.5 films had A2 ordering up to 400 °C and 300 °C annealing temperature, respectively, and they had B2 ordering for the remaining temperatures. Also the crystal structure deteriorated at 600 °C for all of the film systems. The saturation magnetization, M S , of films increased with annealing temperature till 400 °C except Co2MnAl0.5Sn0.5 in which M S increased till 500 °C, which is consistent with the structural analysis. The effective magnetization was obtained from the FMR spectra and it was found that it decreased with increasing Sn-concentration and reached a minimum value at Co2MnAl0.25Sn0.75 composition. Lastly, Co2MnAl1−x Sn x films annealed at 500 °C showed the best crystal ordering. The lowest α value was 0.008 and obtained from Co2MnAl0.5Sn0.5 films annealed at 500 °C.