Atomic-scale Origin of Interfacial Dzyaloshinskii--Moriya Interaction in Pt/Fe/Au

Abstract

Recent results show remarkable interfacial--Dzyaloshinskii--Moriya interaction (i-DMI) in magnetic heterostructures composed of relatively thick Fe thin films ($\gg 1$ nm). To investigate its origin, we present a thorough magnetic characterization of the SiO${}_2$/${}^{57}\mathrm{Fe}$($t$)/Au and SiO${}_2$/Pt/${}^{57}\mathrm{Fe}$($t$)/Au heterostructures ($t=1.6$ - $2.2$ nm). An i-DMI constant of $D_s^{\mathrm{Pt}}=0.43\mathrm{mJ}{\mathrm{m}}^{-2}$ is extracted for the Pt/Fe/Au system, as probed by wavevector-resolved Brillouin light scattering spectroscopy. Ferromagnetic resonance and conversion electron Mössbauer spectroscopy indicate that significant surface anisotropy is present in Pt/Fe/Au, and that an interfacial Fe fraction ($\sim 18$) exhibits tilted magnetization ($\sim 25^{\circ }$ out of plane) and an enhanced hyperfine field, correlating with the stronger i-DMI.