Further study of the Mn2+EPR centre in ferro- and para-elastic BiVO4:spin Hamiltonian parameters and temperature dependence

Abstract

The electron paramagnetic resonance (EPR) of an Mn²⁺ (S=5/2) impurity in the ferroelastic and para-elastic phase of BiVO₄ crystals with a single domain, grown by the Czochralski method, has been investigated using an X-band spectrometer. The rotation patterns of the resonance fields measured on the crystallographic planes are analysed: g=1.9940+or-0.0009, D/h=2.443+or-0.002, E/h=0.4912+or-0.0009, F/h=0.094+or-0.002, B₄²/h=0.0, A_x/h=0.27+or-0.02, A_y/h=0.25+or-0.02, and A_z/h=0.33+or-0.02 GHz at room temperature (T_c). The principal x, y, and z axes of the D-tensor are found to be along the crystallographic b, c+45 degrees and a+45 degrees axes, respectively. This Mn²⁺ centre has the correct principal axes system of the D-tensor compared with the previous Mn_I centre. The D-value decreases as the temperature increases in the range 107-535 K. It is proposed that the Mn²⁺ ion substitutes for Bi³⁺ without nearby charge compensation.