Structural and Magnetic Properties of B-Site-Ordered RE₂CuTiO₆ (RE = Dy, Ho, and Er) Double-Perovskite Oxides with Significant Cryogenic Magnetocaloric Performance

Abstract

The magnetocaloric effect (MCE) is currently intensively investigated in various rare earths (RE)-containing magnetic solids, not only for developing appropriate magnetocaloric materials (MCMs) for cryogenic magnetic cooling but also for deepening our understanding into the inherent physical properties of these materials. Here, we provide a systematic experimental investigation into a series of new RE 2CuTiO6 (RE = Dy, Ho, Er) double-perovskite (DP) oxides regarding the structural and magnetic properties, especially for their cryogenic MCE and magnetic-phase transition (MPT). All of these RE 2CuTiO6 oxides crystallize in a B-site-ordered hexagonal DP-type structure with the symmetry of the crystallographic space group P6̅m2. These DP oxides exhibit magnetic ordering, with MPT temperatures of approximately 2.7, 2.2, and 2.7 K for Dy2CuTiO6, Ho2CuTiO6, and Er2CuTiO6, respectively. The magnetocaloric performances of the RE 2CuTiO6 DP oxides were characterized by the peak values of magnetic entropy change, the temperature-averaged magnetic entropy change (5K-lift), and relative cooling powers. These magnetocaloric parameters were deduced to be 18.7/17.9 J/kgK and 298.2 J/kg for Dy2CuTiO6, 12.5/12.2 J/kgK and 273.9 J/kg for Ho2CuTiO6, and 13.8/12.9 J/kgK and 188.4 J/kg for Er2CuTiO6 under a magnetic field change of 0–5 T. These values are comparable to those of most reported RE-containing magnetocaloric materials, indicating that these RE 2CuTiO6 DP oxides are promising candidates for cryogenic magnetic cooling applications.