Frustrated magnet for adiabatic demagnetization cooling to milli-Kelvin temperatures

Adiabatic demagnetization refrigeration is an efficient technique for reaching mK temperatures. Here, the water-free frustrated magnet KBaYb $${({{\rm{BO}}}_{3})}_{2}$$ ( BO 3 ) 2 is shown to combine cooling efficiency with stability upon exposure to air, vacuum, and heating, providing an alternative to the commonly used water-rich paramagnetic salts.