Experimental study of spin-wave dispersion in Py/Pt film structures in the presence of an interface Dzyaloshinskii-Moriya interaction

Abstract

Brillouin light scattering (BLS), complemented by ferromagnetic resonance (FMR) characterization, has been used for studying spin-wave (SW) propagation in $\mathrm{Py}(L)/\mathrm{Pt}(6\text{\ensuremath{-}}\mathrm{nm})$ bilayers of various Py thicknesses $(4\phantom{\rule{0.16em}{0ex}}\mathrm{nm}\ensuremath{\le}L\ensuremath{\le}10\phantom{\rule{0.16em}{0ex}}\mathrm{nm})$. The FMR measurements allowed determination of the pertinent magnetic parameters and revealed the existence of a normal surface anisotropy. A pronounced asymmetry of Damon-Eshbach (DE) wave frequencies has been evidenced by BLS. Therefore, the difference between Stokes and anti-Stokes DE frequencies has been measured versus SW wave number for all the samples. A detailed discussion about the origin of this frequency difference is reported, which concludes that this is due to interface Dzyaloshinskii-Moriya interaction (IDMI).