  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.
