Low-temperature magnetocaloric behavior of KBaRE(BO3)2 (RE = Gd, Tb): Raman spectroscopic insights

Materials exhibiting large magnetocaloric responses and tunable low-temperature magnetic correlations are of considerable interest for cryogenic refrigeration and the study of rare-earth magnetism. Single crystals of the rare-earth borate series KBaRE(BO3)2 (RE = Gd, Tb) were grown by spontaneous nucleation. X-ray diffraction confirms a trigonal structure with space group R3̄m and triangular-lattice rare-earth layers. The magnetic properties and magnetocaloric effect (MCE) of rare-earth borates KBaRE(BO3)2 (RE = Gd, Tb) were systematically investigated using magnetic susceptibility, isothermal magnetization, and specific heat measurements. No long-range magnetic ordering is observed down to 2 K, while Curie–Weiss analysis and field-dependent susceptibility reveal weak short-range antiferromagnetic correlations at low temperatures. For the Gd-based member, we observe a maximum magnetic entropy change of −ΔSm=15.47J mol⁻¹K⁻¹ at 2 K under μ0H=7 T, reaching ∼90% of the theoretical limit for Gd³⁺. The Tb-based analogue exhibits stronger anisotropy arising from the unquenched orbital moment, offering tunable magnetic correlations within the KBaRE(BO3)2 family. We further investigate the Raman and photoluminescence (PL) properties of the Gd³⁺ and Tb³⁺ ions and analyze how the Raman modes and PL emission features depend on the host lattice composition within the KBaRE(BO3)2 framework. These results establish the RE = Gd, Tb members as a promising platform for studying rare-earth magnetism and low-temperature magnetocaloric behavior.

Duke Scholars

Author Changcheng Zheng DKU Faculty