J. Phys. IV France 07 (1997) C1-243-C1-244
Jahn-Teller Effect in Copper-Doped Spinel GroupV.A. Shapovalov1, H. Szymczak2, S. Piechota2 and V.V. Shapovalov3
1 Donetsk Physico-Technical Institute, Academy of Sciences of Ukraine, R. Luxemburg 72, 340114 Donetsk, Ukraine
2 Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32, 02-668 Warszawa, Poland
3 Department of Physics, Queens College of the City, University of New York, New York, NY 11367, U.S.A.
Anomalous magnetic properties and various phase transitions observed in some spinels are due to the Jahn-Teller effect. The effect is rather effectively studied in corresponding diamagnetic analogues of such crystals. In the present paper a group of single crystals of normal and converted spinels doped with the two-valent copper Cu2+ has been investigated. In this group of spinels the effect of inversion splitting shows itself classically. The investigations have been done by using radiospectrometers of 10 and 37 GHz frequency in the temperature range 4-300 K. For the first time, in the low-frequency range at the frequency of 10 GHz the full complex of the EPR spectra have been registered which are due to the theory of the inversion splitting. It consists of five types of the EPR spectra which are due to allowed 3- -3+, 2--2+, 1- -1+ and forbidden 3--1+, 1+ -2- transitions. At passing to a higher frequency of 37 GHz there occurs the frequency transformation of the spectrum, the two EPR spectra are observed which have been observed by many authors in copper complexes in the case of Jahn-Teller effect developing.
© EDP Sciences 1997