Influence of annealing temperature and capping layer on the structural, magnetic and transport properties of ion beam sputtered Co2FeAl thin films on Si (100)

The impact of different annealing temperatures (Ta) and presence of capping layer on the structural, magnetic and transport properties of sputtered Co2FeAl (CFA (10 nm)) Heusler alloy thin films grown on Si (100) substrate is studied. The structural and topographical study reveal a direct impact of annealing on the crystallinity and surface roughness of the films. The Ferromagnetic resonance study shows that the Gilbert damping constant (alpha) is influenced by both crystallinity and roughness of the films and has a minimum value of 9.35(+/- 0.15) x 10-3 for the 300 degrees C annealed (5.51(+/- 0.27) x 10-3 for Al capped film) film having the lowest surface roughness. Also, the effect of capping layer on the spin dynamic properties of CFA layer is studied which reveals that a protective layer of low spin-orbit coupling material prevents the spin pumping to the formed oxide in case of uncapped CFA. The temperature-dependent resistivity depends on the roughness and crystallinity of the films (which are also a function of Ta) and revealed the dominance of weak localization at lower temperatures and electron-phonon scattering at higher temperatures. Temperature-dependent anomalous Hall effect measurements suggest the supremacy of the combined intrinsic and side jump contributions over skew scattering contribution.