Vibrational properties of SrVO 2 H with large spin-phonon coupling

The antiferromagnetic transition metal oxyhydride SrVO 2 H is distinguished by its stoichiometric composition and an ordered arrangement of H atoms. The tetragonal structure is related to the cubic perovskite and consists of alternating layers of VO 2 and SrH. d 2 V(III) attains a sixfold coordination by four O and two H atoms. The latter are arranged in a trans fashion, which produces H–V–H chains along the tetragonal axis. Here, we investigate the vibrational properties of SrVO 2 H by inelastic neutron scattering and infrared spectroscopy combined with phonon calculations based on density functional theory. The H-based vibrational modes divide into a degenerate bending motion perpendicular to the H–V–H chain direction and a highly dispersed stretching motion along the H–V–H chain direction. The bending motion, with a vibrational frequency of approximately 800 cm −1 , is split into two components separated by about 50 cm −1 , owing to the doubled unit cell from the antiferromagnetic structure. Interestingly, spin-phonon coupling stiffens the H-based modes by 50−100cm −1 although super-exchange coupling via H is very small. Frequency shifts of the same order of magnitude also occur for V–O modes. It is inferred that SrVO 2 H displays the hitherto largest recognized coupling between magnetism and phonons in a material.