Gilbert Damping Constant of Quaternary Co2MnAl1-xSnx Heusler Alloy Thin Films

Abstract

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 (alpha) 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 A degrees C and 300 A degrees C annealing temperature, respectively, and they had B2 ordering for the remaining temperatures. Also the crystal structure deteriorated at 600 A degrees C for all of the film systems. The saturation magnetization, M (S) , of films increased with annealing temperature till 400 A degrees C except Co2MnAl0.5Sn0.5 in which M (S) increased till 500 A degrees 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 A degrees C showed the best crystal ordering. The lowest alpha value was 0.008 and obtained from Co2MnAl0.5Sn0.5 films annealed at 500 A degrees C.