Crystal structure, magnetic property and cryogenic magnetocaloric effect in the antiferromagnetic Ba5Zn4Gd8O21 oxide

Abstract

Cryogenic magnetic refrigeration based on the magnetocaloric effect (MCE) plays a vital role in the field of many technologies, thereby searching for magnetocaloric materials with superior magnetocaloric performances is essential for this field. Here, we have successfully fabricated the polycrystalline Ba₅Zn₄Gd₈O₂₁ oxide with the tetragonal structure (space group: I4/m) by solid-state reaction, and a comprehensive study is conducted on its magnetic property and cryogenic MCE performance by field-dependent magnetization measurement. The analysis of magnetic susceptibility curves in a static magnetic field H = 0.1 T reveals that the Ba₅Zn₄Gd₈O₂₁ oxide order antiferromagnetically at Néel temperature (T_N ≈ 3.6 K). Meanwhile, it exhibits large conventional and inverse cryogenic MCEs due to field induced first-order magnetic phase transition below T_N. The comprehensive magnetocaloric performances are obtained indirectly from the isothermal field-dependent magnetization data, which yields the maximum magnetic entropy change, temperature-averaged entropy change (7 K), refrigerant capacity and relative cooling power values of 16.02 J/kg∙K, 13.91 J/kg∙K, 146.37 J/kg and 178.83 J/kg under the magnetic field change (ΔH) of 0–7 T, respectively. These valuable magnetic and magnetocaloric data provide evidence that the Ba₅Zn₄Gd₈O₂₁ oxide is a promising material for cryogenic magnetic refrigeration, which highlights the potential of Gd-based oxides in this field.