PARAMAGNETIC RESONANCE STUDY AT MILLIMETER WAVELENGTHS OF AN AXIAL FE3+ SPECTRUM IN STRONTIUM TITANATE

Paramagnetic resonance measurements have been made on an axially symmetric spectrum of Fe3+ (configuration 3d5) in SrTiO3. The SrTiO3 sample contained a nominal 0.3% Fe impurity. The results were found to be consistent with the assumption that the spin-Hamiltonian is HS=DO20+G∥·Sz+G ⊥·Sx+(a/120) (O40+5O 44)+(F/180) O40. From room-temperature measurements at 35.0 GHz, 65.1 GHz, 69.4 GHz, and 75.0 GHz, values are obtained for the coupling constants in the spin-Hamiltonian: 2D=(2.707±0.008) cm-1, and (5a/2+5F/3)≅0.01 cm-1. D was determined to be of positive sign in an experiment carried out at 1.2°K and 9.4 GHz. Results of between 25 and 60 G were obtained for the linewidths of some of the transitions. © 1968 The American Institute of Physics.