Paramagnetic Ions in Distorted Perovskite YAlO3 Doped with Europium

In crystals of yttrium orthoaluminate doped with the 151Eu isotope, Eu2+, Cr3+, Gd3+, and Мо3+ paramagnetic centers are detected. The fine structure parameters of the spin Hamiltonian are determined or refined for these centers. The orientation behavior of previously unobserved forbidden transitions is considered for the Cr3+ centers. It is shown that two Mo3+ signals that are detected in magnetic fields directed parallel to the crystallographic axes do not belong to different molybdenum centers, but are two intradoublet transitions of the same center.