Thermal and magnetic effects in quasi-binary Tb1-xDyxNi2 (x = 0.25, 0.5, 0.75) intermetallics

Abstract

Measurements of the low-temperature heat capacity performed for the polycrystalline Tb1-xDyxNi2 intermetallic compounds with x = 0.25, 0.5 and 0.75 enable us to determine their Debye temperatures and estimate the lattice, electron and magnetic contributions to the heat capacity. The measurements in magnetic fields of 1 and 2 T were performed to find the isothermal magnetic entropy and adiabatic temperature changes which characterize the magnetocaloric effect of these compounds. The experimental data obtained are paralleled by theoretical calculations performed in the frame of a microscopic model, which takes into account the exchange interaction and the crystal electric field anisotropy. For the Tb0.75Dy0.25Ni2 compound, direct measurements of the adiabatic temperature change in the temperature range of the magnetic transition were carried out in magnetic fields up to 14 T. The found regularities are discussed in terms of Landau's theory of second-order magnetic phase transitions. In addition, for the parent binary compound, TbNi2, the change of emitted (absorbed) quantity of heat ΔQ was determined using direct measurements.