Giant low-field cryogenic magnetocaloric effect in polycrystalline LiErF₄ compound

Antiferromagnetic LiErF₄ has attracted extensive attention due to its dipolar interaction domination and quantum fluctuations action. In the present work, the crystal structure, cryogenic magnetic properties, and magnetocaloric effect (MCE) of polycrystalline LiErF₄ compound are investigated. Crystallographic study shows that the compound crystallizes in the tetragonal scheelite structure with I4₁/a space group. It exhibits an antiferromagnetic (AFM) phase transition around 0.4 K, accompanied by a giant cryogenic MCE. At 1.3 K, the maximum values of magnetic entropy changes are 24.3 J/kg⋅K, 33.1 J/kg⋅K, and 49.0 J/kg⋅K under the low magnetic field change of 0-0.6 T, 0-1 T, and 0-2 T, respectively. The giant MCE observed above Néel temperature T _N is probably due to the strong quantum fluctuations, which cause a large ratio of the unreleased magnetic entropy existing above the phase transition temperature. The outstanding low-field MCE below 2 K makes the LiErF₄ compound an attractive candidate for the magnetic refrigeration at the ultra-low temperature.