Magnetic entropy change and relative cooling power of Gd3Ni6Al2 and Tb3Ni6Al2 compounds

We present study of the magnetocaloric effects (MCE) in Gd3Ni6Al2 and Tb3Ni6Al2 crystallizing in the Cubic Ce3Ni6Si3-type structure. The two compounds undergo a second-order ferromagnetic transition at Curie temperature TC=105.7 and 57.5 K for Gd3Ni6Al2 and Tb3Ni6Al2, respectively. Magnetization and specific heat are measured as functions of temperature and magnetic field around TC, and the measurements are used to estimate the magnetic entropy change (ΔSm) and the relative cooling power (RCP) by both magnetic and calorimetric techniques. A relatively large ΔSm associated with the ferromagnetic transition has been observed over a wide temperature range for both the compounds, leading to a high RCP. The maximum values of ΔSm in a 5 T magnetic field are evaluated to be 6.2 Jkg−1K−1 for Gd3Ni6Al2 and 9.8 Jkg−1K−1 for Tb3Ni6Al2, the corresponding values of RCP are 608 and 461 Jkg−1, respectively. Particularly, both Gd3Ni6Al2 and Tb3Ni6Al2 show higher RCP values even in a small field change that can be generated by a permanent magnet.