Measurement and interpretation of the magneto-electric effect in TbPO₄

Abstract

TbPO4 shows two successive magnetic phase transitions, the lower of which is connected with a Jahn-Teller induced reduction of crystal symmetry. In both phases, the magneto-electric (ME) effect (which is larger that in other known ionic crystals) was measured to determine the temperature and magnetic-field dependence of the elements of the ME susceptibility tensor. Calculations in mean-field theory taking into account exchange, dipole and Jahn-Teller interactions, a static external field and ME coupling yield quite satisfactory agreement with the measured temperature variation of the elements. Considerable differences exist in the field dependence indicating the deficiency of the theoretical model.