V. I. Torgashev, A. S. Prokhorov, G. A. Komandin, E. S. Zhukova, V. B. Anzin, V. M. Talanov, L. M. Rabkin, A. A. Bush, M. Dressel, B. P. Gorshunov, “Magnetic and dielectric response of cobalt-chromium spinel CoCr$_2$O$_4$ in the terahertz frequency range”, Fizika Tverdogo Tela, 2012, Volume 54, Issue 2,Pages 330

This article is cited in 30 papers

Phase transitions

Magnetic and dielectric response of cobalt-chromium spinel CoCr$_2$O$_4$ in the terahertz frequency range

V. I. Torgashev^a, A. S. Prokhorov^bc, G. A. Komandin^b, E. S. Zhukova^bc, V. B. Anzin^b, V. M. Talanov^d, L. M. Rabkin^a, A. A. Bush^e, M. Dressel^f, B. P. Gorshunov^bc

^a Southern Federal University, Rostov-on-Don
^b Prokhorov General Physics Institute of the Russian Academy of Sciences, Moscow
^c Moscow Institute of Physics and Technology (State University), Dolgoprudny, Moscow region
^d South-Russia State Technical University, Novocherkassk
^e MIREA — Russian Technological University, Moscow
^f Physikalisches Institut, Universität Stuttgart, Stuttgart, Germany

Abstract: The nature of the phonon and magnon modes in the CoCr$_2$O$_4$ multiferroic with a cubic spinel structure has been studied using submillimeter spectroscopy and infrared Fourier spectroscopy. This paper reports on the first measurement of the evolution with temperature of the exchange optical magnon in the ferrimagnetic ($T_C$ = 94 K) and two low-symmetry ($T_S\approx$ 26 K, $T_{\text{lock-in}}$ = 14.5 K) phases of CoCr$_2$O$_4$ down to $T$ = 5 K in zero magnetic field. It has been shown that the detected magnon is not a ferrimagnetic order parameter and originates, most probably, from spin precession in the cobalt sublattices. At the points of the magnetic phase transitions, the oscillator parameters of the two lowest-frequency phonon modes reveal an anomalous temperature behavior, thus evidencing the presence of significant interaction between the magnetic and phonon subsystems. The increase by 25% of the damping parameter of the phonon mode originating from vibrations of the CoO$_4$ tetrahedra during the transition of CoCr$_2$O$_4$ to the multiferroic state $(T<T_S)$ suggests structural changes in the lattice involving loss of spatial central symmetry of the medium.

Received: 20.06.2011