Giant Low-Field Magnetocaloric Effect at Sub-Kelvin Temperatures in Ferromagnetic NH 4 GdF 4

作者：Qing Guo, Weijun Ren, Peng Liu, Jiwei Yao, Junsen Xiang, Kun Zhang, Yanxu Wang, L. S. R. Kumara, Xiao‐Lei Wang, Wei Li, Bing Li · 发表于：Journal of the American Chemical Society · 年份：2025 · DOI：10.1021/jacs.5c10979 · 被引用次数：8 · 研究领域：Magnetic and transport properties of perovskites and related materials、Advanced Condensed Matter Physics、High-pressure geophysics and materials

The development of materials for helium-free sub-Kelvin adiabatic demagnetization refrigeration (ADR) is crucial for advancing research in condensed matter physics, quantum computing, astrophysical measurements in space, and other related fields. Among such materials, Gd 3 Ga 5 O 12 (GGG) has been widely regarded as a benchmark cryogenic refrigerant for ADR systems. In this article, we report on a rare-earth fluoride, NH 4 GdF 4, whose low-field magnetocaloric effect is significantly stronger than that of GGG. NH 4 GdF 4 orders at T c = 0.85 K and exhibits a ferromagnetic ground state at low temperatures as proved by the nearest neighbor exchange interaction model and the specific heat analysis. It has excellent low-field magnetization properties, as evidenced by approaching its saturation magnetization of 160 emu/g below a magnetic field of 10 kOe. Furthermore, the magnetic entropy change of up to 38.2 J·kg –1 ·K –1 and its measured temperature change of 1.1 K at an initial temperature of 1.8 K under the magnetic field change of 0–10 kOe are greater than all reported results and much greater than the entropy change and temperature change of GGG under the same conditions. Thus, NH 4 GdF 4 is a competitive refrigerant candidate for low-field-driven ADR applications at sub-Kelvin temperatures.