Spin-phonon coupling in ZnCr2Se4

Spin-phonon coupling and magnetodielectric effects of ZnCr2Se4 were investigated by means of infrared (IR) spectroscopy as a function of temperature and magnetic field. ZnCr2Se4 is dominated by ferromagnetic exchange but undergoes antiferromagnetic order at T = 21 K. In the magnetically ordered phase the low-frequency IR active phonon splits, indicating strong dynamic anisotropy via magnetic exchange interactions. Antiferromagnetic order and concomitantly the phonon splitting is wiped out by external magnetic fields. Hence, ZnCr2Se4 is a prominent example of a spin-driven Jahn-Teller effect which can be fully suppressed in external magnetic fields.