Giant and reversible low field magnetocaloric effect in LiHoF₄ compound

Abstract

Cryogenic refrigeration technology is gradually penetrating into increasing aspects in human life and industrial production. Magnetic refrigeration shows excellent application potential due to its high efficiency, good stability and environmental...

Giant low-field cryogenic magnetocaloric effect in polycrystalline LiErF4 compound

“…Lithium rare earth tetrafluorides (LiREF 4 ) with the tetragonal scheelite structure were widely studied because their tightly bound 4f electrons are far enough apart that the dipolar interactions dominate exchange interactions. And excellent MCE of LiGdF 4 [21] and LiHoF 4 [22] have been confirmed. The maximum −∆S M values for LiGdF 4 and LiHoF 4 are 44.9 J/kg•K and 25.9 J/kg•K under ∆µ 0 H = 2 T, respectively.…”

Ultralow-field magnetocaloric materials for compact magnetic refrigeration

“…Along the easy axes, the maxima of -ΔS m for LiGdF 4 , LiTbF 4 , LiHoF 4 , LiDyF 4 , LiErF 4 , LiYbF 4, and LiTmF 4 single crystals were 6.6, 10.1, 16.7, 7.8, 6.7, 1.7, and 0.04 J kg −1 K −1 , respectively, when the magnetic field was changed from 0 to 5 kOe, 22.5, 17.9, 21.7, 18.9, 16.1, 6, and 0.16 J kg −1 K −1 , respectively, when the magnetic field was changed from 0 to 10 kOe, and 46.7, 21.2, 25.5, 24.4, 21.9, 14.7, and 0.7 J kg −1 K −1 , respectively, when the magnetic field was changed from 0 to 20 kOe. Under a magnetic field of 5 kOe, LiHoF 4 yielded the largest -ΔS m value among all fluorides, larger than that of polycrystalline LiHoF 4 21 . With increasing magnetic field, LiGdF 4 performed the best under 10 and 20 kOe.…”

“…LiREF 4 has shown great potential as a magnetocaloric material since Numazawa et al investigated the magnetocaloric effects of polycrystalline LiGdF 4 in 2006 23 . Very recently, polycrystalline LiGdF 4 , LiHoF 4, and LiErF 4 have also been reported with entropy changes of 44, 25.9, and 17.5 J kg −1 K −1 , respectively, under 20 kOe 21,23,38 . Due to the high magnetocrystalline anisotropy, the polycrystalline samples exhibited a limited performance under a small magnetic field.…”

“…Since then, GGG has become the primary choice for commercial adiabatic demagnetization refrigerators around the liquid-helium temperature as well as a benchmark for magnetocaloric materials exploration 16,17 . Although an increasing number of low-temperature magnetocaloric materials with large ΔS m values have been reported [18][19][20][21][22] to satisfy the growing demands for space exploration and quantum computation, strong magnetic fields are usually needed, which are currently only provided by heavy and large superconducting magnets. Furthermore, as commercial adiabatic demagnetization refrigerators are usually applied for precision detection in low-temperature environments, magnetic shielding must be considered.…”

Enhancing the performance of magnetic refrigerants through tuning their magnetism from antiferromagnetism to weak ferromagnetism

“…However, on the one hand, magnetic refrigerants are required to possess large MCEs, because the driving force of magnetic refrigeration is magnetic entropy changes (−∆S m ) of magnetic refrigerants [9][10][11]. On the other hand, magnetic refrigeration needs to be carried out under low magnetic fields for its practical application [12][13][14][15]. Although it is known that high magnetic density and paramagnetic or weak ferromagnetic interactions are beneficial to obtaining the large-MCE magnetic refrigerants [16,17], owing to paramagnetic refrigerants often requiring relatively large fields to obtain large MCE [18], the key to obtaining large-MCE magnetic refrigerants under a low magnetic field is to prepare magnetic refrigerants with high magnetic density and weak ferromagnetic exchange simultaneously [19].…”