Characterization of the Interfacial Dzyaloshinskii–Moriya Interaction in Pt/Co2FeAl0.5Si0.5 Ultrathin Films by Brillouin Light Scattering

Brillouin light scattering (BLS) combined with vibrating sample magnetometry (VSM) have been used to investigate the Dzyaloshinskii–Moriya interaction (DMI) in Pt-buffered Co
₂
FeAl
_0.5
Si
_0.5
ultrathin films of various thicknesses. VSM measurements of the Co
₂
FeAl
_0.5
Si
_0.5
(CFAS) thickness dependence of the saturation magnetic moment per unit area revealed a magnetization at saturation of 1286 emu/cm
³
and 0.31 nm magnetic dead layer. Furthermore, thickest films (
$t_{{\text {CFAS}}} >1$
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 anti-Stokes 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/m
²
, which reinforces the perpendicular magnetization easy axis.