Abstract
A sample of HoCo3B2 compound was synthesized, and the magnetic and MCE properties were investigated. Compound shows a change corresponding to R-R (R = rare earth) sublattice magnetic order transition and the transition temperature is determined to be 11.8 K (TC). The characteristic of Arrott plots with positive slope around TC was observed, indicating a second-order phase transition. Based on isothermal magnetization data, together with Maxwell’s relationship, the magnetic entropy change (-ΔSM) was calculated. The maximum -ΔSM reaches 7.8, 12.7 and 14.4 J/kg K for field range of 0-2 T, 0-5 T and 0-7 T, respectively. Accordingly, the value of RC (refrigerant capacity) is 99, 289 and 432 J/kg for above field ranges. The large MCE of HoCo3B2 compound indicates its potential application for magnetic refrigeration in low temperature range.
Highlights
magnetocaloric effect (MCE) is an intrinsic property of magnetic materials and it is usually evaluated by the isothermal magnetic entropy change (-∆SM), adiabatic temperature change (∆Tad) and refrigerant capacity (RC)
ErCo2 compound is a kind of representative low temperature MCE material because of its giant MCE, and it has been considered as a referenced material in low temperature range.[21,22]
It is necessary to search for magnetic materials with large and reversible MCE based on the second-order magnetic transition
Summary
Compared with traditional gas compression/expansion technology, the magnetic refrigeration technology based on magnetocaloric effect (MCE) has the advantages of environmental friendliness and high energy efficiency.[1,2,3,4] MCE is an intrinsic property of magnetic materials and it is usually evaluated by the isothermal magnetic entropy change (-∆SM), adiabatic temperature change (∆Tad) and refrigerant capacity (RC). Are the extreme case for n= infinite and they crystallize in the hexagonal (P6/mmm) CaCu5-type structure.[23,24,25,26,27,28,29,30,31] It can be imagined as being built up by ordered substitutions of B atoms into the Co sites in an RCo5-type structure.[24,25,26,27,28,29,31] Recently, the system of RCo3B2 (R=Gd, Sm, Tb, Dy, Ho) has been studied for electronic and magnetic properties.[24,25,26,27,28,29,30,31] Some of RCo3B2 series are paramagnetic and some are ferromagnetically ordered at low temperatures.[28] Especially, GdCo3B2 compound has been proved to undergo two magnetic transitions at 54 K and 160 K respectively while increasing the temperature.[32] TbCo3B2 compound was described to experience two magnetic transitions according to Dubman[26] et al, but only one transition temperature was observed by Li33 et al Large MCE has been found in GdCo3B2, TbCo3B2 and DyHo3B2 compounds.[32,33,34,35] The magnetic and crystallographic properties of HoCo3B2 compound[30] have been investigated before, no research work on MCE has been reported. The magnetic and MCE properties of HoCo3B2 compound is studied in detail
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