Crystal structure, magnetic properties and cryogenic magnetocaloric performance of garnet RE3Al5O12 (RE = Tb, Dy and Ho) compounds

Abstract

The magnetic refrigeration (MR) based on the principle of magnetocaloric effect (MCE) in magnetic materials was recognized as an alternative cooling way to our present commercialized vapor compression cycle technology. Evidently, a vital prerequisite for practical applications is the exploration of candidate materials with prominent magnetocaloric performances. In this paper, the polycrystalline garnet RE₃Al₅O₁₂ (RE = Tb, Dy and Ho) compounds with the cubic structure (space group: $Ia\overline{3}d$) were prepared using the Pechini sol–gel method, and their crystal structure, magnetic properties and comprehensive magnetocaloric performances were studied. The analysis of magnetic susceptibility curves in a static magnetic field H = 0.1 T reveal that the Dy₃Al₅O₁₂ undergoes antiferromagnetic transition with Néel temperature T_N ≈ 2.6 K, whereas the Tb₃Al₅O₁₂ and Ho₃Al₅O₁₂ exhibit no features indicative of the magnetic ordering processes down to 1.8 K. The comprehensive magnetocaloric performances, namely the maximum magnetic entropy change and relative cooling power, are derived indirectly from the isothermal field-dependent magnetization data, which yield 11.72, 10.42, 7.53 J/(kg·K) and 84.56, 69.52, 70.35 J/kg for the Tb₃Al₅O₁₂, Dy₃Al₅O₁₂ and Ho₃Al₅O₁₂ under a low field change (ΔH) of 0–2 T, respectively. The superior comprehensive magnetocaloric performances and wide operating temperature range of these compounds under low ΔH make them attractive for cryogenic MR technology.