Magnetoelectric Effects in TbPO[sub 4]

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 Neel 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...