JAHN-TELLER EFFECT IN COPPER-DOPED SPINEL GROUP

Anomalous magnetic properties and various phase transitions observed i n some spinels are due to the Jahn-Teller effect. The effect is rather effectively studied in corresponding diamagnetic analogues of such cr ystals. In the present paper a group of single crystals of normal and converted spinels doped with the two-valent copper Cu2+ has been inves tigated. In this group of spinels the effect of inversion splitting sh ows itself classically. The investigations have been done by using rad iospectrometers 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 whi ch are due to the theory of the inversion splitting. It consists of fi ve 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 transforma tion of the spectrum,the two EPR spectra are observed which have been observed by many authors in copper complexes in the case of Jahn-Telle r effect developing.