Measurement of the spin-strain coupling tensor in ruby by ultrasonically-modulated EPR

The strain-dependent line-shifts of EPR transitions in ruby have been measured using the UMER (ultrasonically-modulated EPR) technique. Results were obtained for four transitions for a range of magnetic field orientations perpendicular to an applied uniaxial stress and for angles of 0 degrees , 45 degrees and 90 degrees between stress and three-fold axis. These have been fitted by a perturbation Hamiltonian G ijkl S i S j epsilon kl yielding values for the spin-strain tensor G. Some combinations of the tensor elements of a small delta g term were also obtained. The G tensor obtained for Cr 3+ in a trigonal distortion is similar to that obtained by rotating values for Cr 3+ in O h symmetry (MgO) into the same coordinates.