Correlation between the structure and thermomagnetic properties of pseudo-binary (Tb,Er)Ni2 solid solutions

Abstract Magnetic and thermodynamic properties, the isothermal magnetic entropy change ΔSmag is among them, of the polycrystalline pseudo-binary Tb1-xErxNi2 (x = 0.25, 0.5, and 0.75) solid solutions are studied in accordance with the erbium substitution for terbium, which causes changing the crystal structure. The Tb1-xErxNi2 solid solutions at room temperature were found to have the C15 Laves-phase superstructure rather than the C15 structure typical of the parent compounds, TbNi2 and ErNi2. Moreover, as was shown by magnetic measurements, the substitution of Er for Tb in Tb1-xErxNi2 results in the decrease in the ordering temperature of the pseudo-binary compounds, which corresponds to the second-order ferromagnet to paramagnet magnetic phase transition; in the case of x = 0.25 and x = 0.75, the decrease is from 29.0 to 13.6 K, respectively. The isothermal magnetic entropy change, which is estimated to characterize the magnetocaloric properties of the pseudo-binary compounds, was analyzed using the thermomagnetic Maxwell relation and in terms of the Landau theory of phase transitions. The maximum magnetic entropy change of the Tb0·75Er0·25Ni2, Tb0·5Er0·5Ni2 and for Tb0·25Er0·75Ni2 compositions reaches 6.6 (12.7), 6.9 (13.8) and 7.5 (14.9) J/kgK for a magnetic field change of 2 (5) T, respectively. The relatively large reversible and close values of ΔSmag allow us to state that these pseudo-binary solid solutions show promise as materials for magnetic refrigerators operating within a specific low-temperature range.