SINGLE-CRYSTAL EPR-SPECTRUM OF CR-3+ IN LANTHANUM LUTECIUM GALLIUM GARNET

The Cr3+ EPR spectra of YAG type crystals normally consist of four peaks whose positions are dependent on the axial zero-field splitting D with axis along a [111] direction and angle-theta between that direction and the applied field H0. In LLGG only three principal peaks are observed with zero-field axis nearly along x, y or z. This anomaly is attributed to the relatively small size of Cr3+ compared to Lu3+ which it displaces in an octahedral site. D varies slightly for the different zero-field axes: 0.480 cm-1 along x, 0.429 cm-1 along y and 0.470 cm-1 along z. The spectroscopic splitting factor g = 1.978 +/- 0.001 is essentially isotropic and independent of axes within the experimental error.