Magnetoelectric Effects in TbPO[sub 4

Abstract

It is shown experimentally that the antiferromagnet TbPO4 exhibits a linear magnetoelectric (ME) effect and that its ME susceptibility tensor α↔ has a component αaa whose largest absolute value is considerably larger than any component of α↔ previously reported for any material. Here a denotes one of the axes (a, a′, c) of the tetragonal crystal structure existing above the Néel temperature. The electrically as well as the magnetically induced ME effect was used to measure the temperature (T) dependence of ∣αaa∣ on a single crystal which had been annealed magnetoelectrically (with an appropriate electric field and a necessarily “small” magnetic field) so as to maximize ∣αaamid;. The largest value of ∣αaa∣ is ∣αaa∣max = 11 × 10−3 Gaussian units and occursat T = 1.92 ± 0.01°K. Using the previously proposed atomic mechanism 1 of the ME effect in rare earth crystals and the fragmentary spectroscopic data presently available, we compare this value of ∣αaa∣max with the value ∣αaa∣max = 1.2 × 10−3 Gaussian units measured 1 in ME‐annealed DyPO4. While we are still investigating the symmetry of magnetoelectrically annealed TbPO4, we have concluded from suitable ME experiments that the symmetry of non‐annealed TbPO4 in the antiferromagnetic state is lower than tetragonal. For sufficiently large absolute values of a biasing magnetic field H oriented parallel to either a, a′, or c, the dependence of αaa on H reveals abrupt magnetic transitions, hysteresis, and switching effects. A full account of this work will be published elsewhere.