Achieving Magnetic Refrigerants with Large Magnetic Entropy Changes and Low Magnetic Ordering Temperatures

Adiabatic demagnetization refrigeration (ADR) is a promising cooling technology with high efficiency and exceptional stability in achieving ultralow temperatures, playing an indispensable role at the forefront of fundamental and applied science. However, a significant challenge for ADR is that existing magnetic refrigerants struggle to concurrently achieve low magnetic ordering temperatures (T₀) and substantial magnetic entropy changes (-ΔS_m) at ultralow temperatures. In this work, we propose the combination of Gd³⁺ and Yb³⁺ to effectively regulate both -ΔS_m and T₀ in ultralow temperatures. Notably, the -ΔS_m values for Gd_0.1Yb_0.9F₃ (1) and Gd_0.3Yb_0.7F₃ (2) in the 0.4-1.0 K range exceed those of all previously reported magnetic refrigerants within this temperature interval, positioning them as the most efficient magnetic refrigerants for the third stage to date. Although the -ΔS_m values for Gd_0.5Yb_0.5F₃ (3) in 1-4 K are less than those of the leading magnetic refrigerant Gd(OH)F₂, the -ΔS_m values for Gd_0.7Yb_0.3F₃ (4) in 1-4 K at 2 T surpass those of all magnetic refrigerants previously documented within the same temperature range, making it the superior magnetic refrigerant for the fourth stage identified thus far.