The buffer layer effect of the exchange stiffness constants on Co thin film

Abstract

The exchange stiffness of Cobalt thin films with various buffer layers (Pd, Pt, Ta, and no buffer) has been studied by Brillouin scattering in the applied magnetic field of up to 175 mT. We found that Pd and Pt buffer layers led to higher exchange stiffness constants more than 12% compared to the Ta buffer layer, whereas, it was difficult to determine the exchange stiffness constant with no buffer layer due to broad spinwave spectra with poor signal-to-noise ratios. The determined exchange stiffness constant value is 25.7 ± 0.1, 25.6 ± 0.2, and 22.7 ± 0.1 pJ/m for Pd, Pt, and Ta buffer layers. We also observed that the Pd-underlayered sample gives us the largest saturation magnetization and in contrast the Ta underlayer shows the relatively smaller values. This observation indicates that the exchange stiffness constant and the saturation magnetization exhibit the same trend on various buffer layers.