Magnetic properties and excellent cryogenic magnetocaloric performances in B-site ordered RE2ZnMnO6 (RE = Gd, Dy and Ho) perovskites

The solid-state magnetic cooling (MC) relying on magnetocaloric effect (MCE) of magnetic materials is recognized as a promising energy efficiency and environmentally friendly technology. However, there is still a large gap between the fundamental materials in the laboratory developing stage and the practically realizable applications. In this paper, a new series of B-site ordered RE2ZnMnO6 (RE = Gd, Dy and Ho) perovskites are successfully fabricated, and their structural and magnetic properties together with the cryogenic magnetocaloric performances are studied in detail. All the RE2ZnMnO6 compounds are found to crystallize in the B-site ordered orthorhombic (double perovskites) structure with the space group of P121/C1. The magnetic ground state are confirmed to be a ferromagnetic (FM) coupling for Gd2ZnMnO6, whereas, ferrimagnetic (FIM) coupling for Dy2ZnMnO6 and Ho2ZnMnO6 based on the magnetic measurements and first principle calculations. The ordering temperatures (TM) are determined to be ~6.4 K for Gd2ZnMnO6, ~10.4 K for Dy2ZnMnO6, and ~6.8 K for Ho2ZnMnO6, respectively. Furthermore, several vital parameters for determining the magnetocaloric performances including -ΔSMmax (magnetic entropy change peak values), TEC(2) (temperature-averaged magnetic entropy change) and RCP (relative cooling powers) are evaluted to be 15.17, 14.44 J/(kgK) and 226 J/kg for Gd2ZnMnO6, 8.32, 8.17 J/(kgK) and 208 J/kg for Dy2ZnMnO6, and 13.19, 12.68 J/(kgK) and 246 J/kg for Ho2ZnMnO6, with the field change ΔH = 50 kOe, respectively. It is worthly noted that Gd2ZnMnO6 exhibits relatively great magnetocaloric performances below 10 K, which suggests that Gd2ZnMnO6 is a competitive candidate for cryogenic magnetic cooling.