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

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 2 CuTiO 6 ( 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 2 CuTiO 6 oxides crystallize in a B -site-ordered hexagonal DP-type structure with the symmetry of the crystallographic space group P 6̅ m 2. These DP oxides exhibit magnetic ordering, with MPT temperatures of approximately 2.7, 2.2, and 2.7 K for Dy 2 CuTiO 6, Ho 2 CuTiO 6, and Er 2 CuTiO 6, respectively. The magnetocaloric performances of the RE 2 CuTiO 6 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 Dy 2 CuTiO 6, 12.5/12.2 J/kgK and 273.9 J/kg for Ho 2 CuTiO 6, and 13.8/12.9 J/kgK and 188.4 J/kg for Er 2 CuTiO 6 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 2 CuTiO 6 DP oxides are promising candidates for cryogenic magnetic cooling applications.