Exceptional Cooling Capacity of LiGdYbF at Sub-Kelvin Temperatures.

Adiabatic demagnetization refrigeration, which utilizes the magnetocaloric effect of magnetic refrigerants, stands as the sole cooling technology capable of achieving sub-Kelvin temperatures efficiently and reliably without relying on scarce He resources or gravity. However, current sub-Kelvin magnetic refrigerants encounter challenges such as structural instability in vacuum or under mild heating, along with small magnetic entropy change (-ΔS) values, which significantly limit their practical applications. Here a water-free magnetic refrigerant, LiGdYbF is reported, prepared by introducing Li⁺ ions to reduce the dipolar interactions between Gd ions and/or Yb ions. Notably, this refrigerant possesses a magnetic ordering temperature of 85 mK, while its experimental -ΔS reaches up to 136 mJ cm K (0.68 K and 2 T), more than three times the theoretical value of CrK(SO)·12HO. Significantly, this refrigerant not only cools the test sample to temperatures as low as 160 mK but also achieves a specific cooling capacity of 46.943 mJ cm T at 300 mK. Remarkably, the specific cooling capacity at 300 mK is more than double that of commercial CrK(SO)·12HO, representing one of the most notable values reported among all known magnetic refrigerants operating at sub-Kelvin temperatures.