Low Temperature Physics: 34, 1015 (2008); https://doi.org/10.1063/1.3029755 (4 pages)
Fizika Nizkikh Temperatur: Volume 34, Number 12 (December 2008), p. 1289-1293    ( to contents , go back )

Schottky-type anomaly of linear optical birefringence of the antiferromagnetic LiCoPO4 crystal

N.F. Kharchenko, Yu.N. Kharchenko, and O.V. Miloslavskaya

B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine 47 Lenin Ave., Kharkov 61103, Ukraine
E-mail: kharchenko@ilt.kharkov.ua

Received Jule 23, 2008, revised August 6, 2008

Abstract

The anomalous behavior of the linearly polarized light birefringence was revealed in the antiferromagnetic magnetoelectric LiCoPO4 crystal at temperatures close to the Néel temperature. We suppose that the observed non-monotonous changes of light birefringence result from the competition of two anomalies: (i) a magnetic anomaly connected with the enhancing contribution of correlated spin fluctuations and (ii) a Schottky-type anomaly caused by changing populations of the ground and the lowest excited electron states of Co2+ ions, these suppositions being supported by the arguments. The evaluated energy distance to the excited state (45–55 K) agrees sufficiently well both with the position of the weakly dispersed branch in the energy spectrum observed at the studies of inelastic scattering of this crystal, and with the position of low-energy bands in the Raman scattering spectrum.

PACS: 75.50.Ee Antiferromagnetic materials;
PACS: 75.30.Kz Magnetic phase boundaries;
PACS: 78.20.Fm Birefringence.

Key words: antiferromagnetic, linear birefringence, LiCoPO4, Schottky-type anomaly.

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