Characterization of the Interfacial Dzyaloshinskii–Moriya Interaction in Pt/Co₂FeAl_0.5Si_0.5 Ultrathin Films by Brillouin Light Scattering

摘要

Brillouin light scattering (BLS) combined with vibrating sample magnetometry (VSM) have been used to investigate the Dzyaloshinskii-Moriya interaction (DMI) in Pt-buffered Co₂FeAl_0.5Si_0.5 ultrathin films of various thicknesses. VSM measurements of the Co₂FeAl_0.5Si_0.5 (CFAS) thickness dependence of the saturation magnetic moment per unit area revealed a magnetization at saturation of 1286 emu/cm3 and 0.31 nm magnetic dead layer. Furthermore, thickest films (t_CFAS >1 nm) are in-plane magnetized, while the thinner ones are perpendicular magnetized. BLS measurements, in the Damon-Eshbach geometry, under an in-plane applied magnetic field revealed the non-reciprocity of the spin waves (SWs) propagating in opposite directions (Stokes and antiStokes lines) due to the Pt-induced DMI. Stokes and anti-Stokes lines' frequency mismatch varies linearly as function of the SW vector allowing the determination of the effective DMI constant. Its thickness dependence leads to determine a value of -0.42 pJ/m for the DMI interface constant, which is significantly lower than that of Pt/Co/AlO_x films. Moreover, BLS measurements revealed that the effective magnetization varies linearly with the reciprocal effective CFAS thickness due to the perpendicular interface anisotropy, estimated to be 0.49 mJ/m2, which reinforces the perpendicular magnetization easy axis.