Refrigeration down to 0.16 K using a frustrated magnet Gd2B2MoO9

Magnetic refrigeration, utilizing the magnetocaloric effect in solid-state magnets, has emerged as a promising cooling technology. The development of practical ultra-low-temperature magnetic refrigeration applications has been limited by the absence of high-performance magnetic refrigerants. Herein, we provide a frustrated Gadolinium-dominated magnet, Gd2B2MoO9 oxide, which exhibits remarkable ultra-low temperature magnetocaloric performances. The maximum magnetic entropy changes reach 13.3 (76.6), 33.7 (194.0) and 45.1 (259.8) J/kgK (mJ/cm3K) under relatively low magnetic field changes of 0-1, 0-2 and 0-3 T, respectively. A minimum temperature of 0.16 K has been achieved by a custom-built quasi-adiabatic demagnetization apparatus. These magnetocaloric performances surpass those of the commercial ultra-low temperature magnetic refrigerant Gd3Ga5O12 and outperform most of recently reported materials. Combined with its relatively high density and environmental stability, the geometrically frustrated Gd2B2MoO9 oxide is established as an attractive ultra-low temperature magnetic refrigerant. Ultra-low-temperature magnetic refrigeration is strongly dependent on the performances of refrigerants. Here the authors provide a frustrated magnet Gd2B2MoO9 with excellent magnetocaloric performances and a minimum temperature of 0.16 K is achieved.