Compositional dependence of interfacial spin-orbit phenomena in Co$_{\mathrm{x}}$Fe$_{\mathrm{1-x}}$/Pt bilayers

We experimentally investigate the dependence of the interfacial Dzyaloshinskii--Moriya interaction (DMI) on the alloy composition in Co$_{\mathrm{x}}$Fe$_{\mathrm{1-x}}$/Pt bilayers. Following the methods in Ref. [1] we use Brillouin light scattering to determine the magnitude of the spin-wave dispersion shift induced by the antisymmetric exchange, allowing us to determine the strength of the DMI constant as a function of Co concentration x. Interestingly, the DMI constant varies significantly as a function of x and peaks at approximately x$=$0.5. These results are compared to measurements of the Heisenberg exchange obtained from fitting Bloch's law to temperature dependent magnetometry data. [1] H. T. Nembach et al., Nature Physics 11, 825--829 (2015)