EPR of Ru3+ in LuAlG and LuGaG

EPR data were determined at 4.2°K for Ru³⁺ impurities located at the octahedral sites of two lutetium garnets and yield the following $g$ values: $\text{g‖\hspace{0.17em}=\hspace{0.17em}3.161, g⊥\hspace{0.17em}=\hspace{0.17em}1.136}$ in LuGaG and $\text{g‖\hspace{0.17em}=\hspace{0.17em}2.907, g⊥\hspace{0.17em}=\hspace{0.17em}1.286}$ in LuAlG. From these data the dependence of the trigonal field parameter $\upsilon$ on polar angle is derived and represented by a quadratic function of the angular distortion of the ideal octahedron. From this dependence it is concluded that the observed trigonal fields can not be explained as arising from the superposition of a positive point‐charge field onto a larger negative field of the ligands.