Electron Spin Resonance of Fe³⁺ in BaTiO₃ at Low Temperatures

Abstract

The electron spin resonance of Fe³⁺ ion in the orthorhombic and rhombohedral phases of BaTiO₃ has been studied. Distinct spectral lines were obtained at orthorhombic phase by biasing the crystal upon cooling. At orthorhombic phase, sign of D was found to be reversed to that of \acutea and E has been verified to be vanishingly small. At rhombohedral phase, both intense spectrum with cubic field splitting and a weak anisotropic spectrum have been observed. The pertinent spin Hamiltonian parameters are determined in these two mentioned phases. Calculations of field gradient components based on the ionic model are given and compared with experiment. Some comments and conjectures are offered as to possible correlation of these results with existing theories on S-state ion and on ferroelectric BaTiO₃.