Collective Mode Splitting in Coupled Ferromagnet/Oxide Heterostructures*

The coupling of electronic, magnetic, and structural properties between two dissimilar materials in contact can induce novel functionalities. Here we report on a drastic modification of the magnetization dynamics of thin Nickel films in Ni/V$_{\mathrm{2}}$O$_{\mathrm{3}}$ bilayers. We performed temperature-dependent ferromagnetic resonance measurements across the first-order structural phase transition (SPT) of V$_{\mathrm{2}}$O$_{\mathrm{3}}$. The results show a strong coupling of the V$_{\mathrm{2}}$O$_{\mathrm{3}}$ lattice dynamics to the magnon spectra of the Ni film in proximity. We have performed similar measurements across the second-order SPT in Ni/SrTiO$_{\mathrm{3}}$ hybrids. In this later case, only a slight change of the static magnetization was found with no modification of the magnetization dynamics. Our results suggest that the phase coexistence across the first-order SPT of V$_{\mathrm{2}}$O$_{\mathrm{3}}$ is responsible for the effects observed in the Ni/V$_{\mathrm{2}}$O$_{\mathrm{3}}$ hybrids. This suggests the existence of similar effects in other hybrid materials with first-order structural phase transitions.