Effect of growth rate on structural, magnetic and spin dynamic properties of Co2FeAl thin films

Abstract

The growth of high-quality Heusler alloy thin films with low damping is essential for designing low-power spintronic devices. Here, we report a systematic investigation of the structural, magnetic, and spin dynamic properties of Co-based (Cobalt, Iron, Aluminum) Heusler alloy Co2FeAl thin films via growth rate variation in sputtering. We found close stoichiometry comparable with the sputtering target towards higher growth rates. However, the stoichiometry of the films is off from the target at relatively low growth rates. The change in stoichiometry can be understood from the variation in the sputtering yield of each element present in the alloy. Grazing incidence X-ray diffraction patterns show that the films with different compositions have the A2 structure. However, the crystallite size strongly depends on the composition. Magneto-optic Kerr effect hysteresis measurements show low coercivity for all the samples, indicating soft magnetic behavior. Spin dynamics study using ferromagnetic resonance reveals that the film with close stoichiometry with the target exhibits the lowest damping parameter, i.e., 0.00448. Our results demonstrate the importance of sputtering growth rate on the structural, elemental, and magnetic properties of Heusler alloy thin films for spintronic device applications.