Successive magnetic transitions and magnetocaloric effects in intermetallic compounds RE7Rh3 (RE = Nd, Ho)

Abstract In this work, the structure, cryogenic magnetic transition behaviors and magnetocaloric properties in the intermetallic compounds RE7Rh3 (RE = Nd, Ho) have been investigated. Powder X-ray diffraction confirmed the formation of RE7Rh3 (RE = Nd, Ho) with hexagonal Th7Fe3-type crystal structure (space group P63mc). For the Nd7Rh3 compound, it exhibits two successive magnetic phase transitions with increasing temperature, that is, a first-order ferromagnetic-antiferromagnetic transition at Tt = 11.3 K and a second-order antiferromagnetic-paramagnetic transition at TN = 33 K. The reciprocal magnetic susceptibility of the Nd7Rh3 compound obeys the Curie-Weiss law in the paramagnetic region. According to Curie constant, the values of the effective magnetic moment (μeff) and the corresponding paramagnetic Curie temperature (θP) are determined to be 3.39 μB/Nd3+ and 38.6 K, respectively. While for Ho7Rh3, it undergoes paramagnetic to antiferromagnetic transition at TN = 33.5 K followed by the other two magnetic transitions states at Tt = 23.5 K and TSR = 7.2 K with decreasing temperature. The effective magnetic moment of Ho7Rh3 is evaluated to be 10.2 μB/Ho3+, and the negative value of paramagnetic Curie temperature (−10 K) indicates the dominant antiferromagnetic interaction in the Ho7Rh3 compound. For a magnetic field change of 5 T, the maximum magnetic entropy changes of Nd7Rh3 and Ho7Rh3 are calculated to be 6.40 J/kg K and 3.06 J/kg K with the corresponding refrigerant capacity values of 164 J/kg and 85 J/kg, respectively.