Structural, magnetic and magnetocaloric properties of HoNi 2 and ErNi 2 compounds ordered at low temperatures

Abstract In this work we report on the structural, magnetic and magnetocaloric properties of polycrystalline HoNi 2 and ErNi 2 Laves-phase compounds. Powder X-ray diffraction studies at room temperature show that the compounds crystallize in the cubic C15 structure (MgCu 2 type). The magnetic measurements reveal that the second-order magnetic phase transition from ferromagnetic to paramagnetic state appears at T C equal 13.5 K for HoNi 2 and 6.5 K for ErNi 2 . Using direct measurements over a wide field range (up to 11 T), along with indirect methods, we have found low and high field regularities of the magnetocaloric effect characterized by the adiabatic temperature change, ΔT ad , and the isothermal magnetic entropy change, ΔS mag . The magnetocaloric properties near the phase transition are discussed in the framework of the Landau theory for the second-order phase transitions.