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

The magnetocaloric effect (MCE) is currently intensively investigated in various rare earths ()-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 CuTiO ( = 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 CuTiO oxides crystallize in a -site-ordered hexagonal DP-type structure with the symmetry of the crystallographic space group 6̅2. These DP oxides exhibit magnetic ordering, with MPT temperatures of approximately 2.7, 2.2, and 2.7 K for DyCuTiO, HoCuTiO, and ErCuTiO, respectively. The magnetocaloric performances of the CuTiO 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 DyCuTiO, 12.5/12.2 J/kgK and 273.9 J/kg for HoCuTiO, and 13.8/12.9 J/kgK and 188.4 J/kg for ErCuTiO under a magnetic field change of 0-5 T. These values are comparable to those of most reported -containing magnetocaloric materials, indicating that these CuTiO DP oxides are promising candidates for cryogenic magnetic cooling applications.