Eur. Phys. J. B 68, 153-160 (2009)
https://doi.org/10.1140/epjb/e2009-00096-4

Optical properties of ZnCr₂Se₄

Spin-phonon coupling and electronic d-d-like excitations

¹ Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany
² Institute of Applied Physics, Academy of Sciences of Moldova, MD-2028 Chişinău, Republic of Moldova

Corresponding author: ^a torsten.rudolf@physik.uni-augsburg.de

Received: 16 July 2008
Revised: 17 October 2008
Published online: 18 March 2009

Abstract

We studied the optical properties of antiferromagnetic ZnCr₂Se₄ by infrared spectroscopy up to 28,000 cm^-1 and for temperatures from 5 to 295 K. At the magnetic phase transition at 21 K, one of the four phonon modes reveals a clear splitting of 3 cm^-1 as a result of spin-phonon coupling, the other three optical eigenmodes only show shifts of the eigenfrequencies. The antiferromagnetic ordering and the concomitant splitting of the phonon mode can be suppressed in a magnetic field of 7 T. At higher energies we observed a broad excitation band which is dominated by a two-peak-structure at about 18,000 cm^-1 and 22,000 cm^-1, respectively. These energies are in good agreement with the expected spin-allowed crystal-field transitions of the Cr³⁺ ions. The unexpected strength of these transitions with d-d character is attributed to a considerable hybridization of the selenium p with the chromium d orbitals.