An X- and Q-band Gd3+ EPR study of a single crystal of EuAlO3: EPR linewidth variation with temperature and low-symmetry effects

Detailed electron paramagnetic resonance (EPR) studies on a single crystal of Gd3+-doped Van-Vleck compound EuAlO3, potentially a phosphorescent/luminescent/laser material, with the Gd3+ ion substituting for the Eu3+ ion, were carried out at X-band (9.2 GHz) over the 77–400 K temperature range. They provide new physical results on magnetic properties of the Eu3+ ion in a low symmetry environment. The asymmetry exhibited by the variation of the Gd3+ EPR line positions for the orientations of the external magnetic field about the Z and X magnetic axes in the ZX   plane was ascribed to the existence of low, monoclinic, site symmetry, as revealed by the significant values of the spin-Hamiltonian (SH) parameters b41 and b43, estimated by fitting all the observed EPR line positions at room temperature for the orientation of the magnetic field in the magnetic ZX plane using a least-square fitting procedure. The temperature dependence of the Gd3+ EPR linewidth is interpreted to be due to the “life-time” broadening, caused by dynamical exchange and dipolar interactions between the impurity Gd3+ ions and the host Eu3+ ions.