Phase transitions and magnetocaloric and transport properties in off-stoichiometric GdNi2Mnx

The structural, magnetic, magnetocaloric, transport, and magnetoresistance properties of the rare-earth intermetallic compounds GdNi2Mnx (0.5 <= x <= 1.5) have been studied. The compounds with x = 0.5 and 0.6 crystallize in the cubic MgCu2 type phase, whereas samples with x >= 0.8 form a mixed MgCu2 and rhombohedral PuNi3 phase. A second order magnetic phase transition from a ferromagnetic to paramagnetic state was observed near the Curie temperature (T-C). The GdNi2Mnx (0.5 <= x <= 1.5) compounds order in a ferrimagnetic structure in the ground state. The largest observed values of magnetic entropy changes (at T-C for Delta H = 5T) were 3.9, 3.5, and 3.1 J/kg K for x = 0.5, 0.6, and 0.8, respectively. The respective relative values of the cooling power were 395, 483, and 220 J/kg. These values are greater than some well-known prototype magnetocaloric materials such as Gd (400 J/kg) and Gd5Si2Ge2 (240 J/kg). Analysis of the resistivity data showed a T-2 dependence at low temperatures, suggesting strong electron-phonon interactions, whereas at higher temperatures s-d scattering was dominated by the electron-phonon contribution, resulting in a slow increase in resistivity. Magnetoresistance values of similar to-1.1% were found for x = 0.5 near T-C, and -7% for x = 1.5 near T = 80 K. (C) 2016 AIP Publishing LLC.