Magnetic properties of Tb _(1 - x)Er _xFe _3(BO _3) _4 (x = 0.75, 1)

摘要

The magnetic properties of antiferromagnets with trigonal symmetry, namely, Tb _(1 - x)Er _xFe _3(BO _3) _4 (x = 0. 75, 1), have been investigated theoretically. The calculations have been performed in the molecular field approximation and in the framework of the crystal field model for the rare-earth subsystem. For the Tb _(0. 25)Er _(0. 75)Fe _3(BO _3) _4 antiferromagnet, the anomalies revealed in the magnetization curves measured during the spin-flop transition induced by a magnetic field B {pipe} c and their evolution with variations in the temperature have been described, as well as the temperature dependences of the initial magnetic susceptibility at temperatures down to 80 K. The existence of a low-temperature Schottky-type anomaly in the magnetic susceptibility curve for a magnetic field B {pipe} c has been predicted. For the ErFe _3(BO _3) _4 system, the experimental data obtained for the magnetization in magnetic fields up to 15 T at temperatures ranging from 4. 2 to 70 K, as well as the temperature dependences of the magnetic susceptibility at temperatures up to 350 K, have been interpreted. The description of the contribution from the rare-earth subsystem to the heat capacity of Tb _(1 - x)Er _xFe _3(BO _3) _4 (x = 0, 1) has allowed us to predict the character of the rare-earth contribution to the heat capacity of Tb _(0. 25)Er _(0. 75)Fe _3(BO _3) _4.