Abstract
Orthorhombic CeNiSi2-type polycrystalline RNiSi2 (R=Gd, Dy, Ho, Er, Tm) compounds were synthesized and the magnetic and magnetocaloric properties were investigated in detail. The transition temperatures of RNiSi2 compounds are all in a very low temperature range (<30 K). As temperature increases, all of the compounds undergo an AFM to PM transition (GdNiSi2 at 18 K, DyNiSi2 at 25 K, HoNiSi2 at 10.5 K, ErNiSi2 at 3 K and TmNiSi2 at 3.5 K, respectively). ErNiSi2 compound shows the largest (ΔSM)max (maximal magnetic entropy change) among these compounds. The value of (ΔSM)max is 27.9 J/kgK under a field change of 0-5 T, which indicates that ErNiSi2 compound is very competitive for practical applications in low-temperature magnetic refrigeration in the future. DyNiSi2 compound shows large inverse MCE (almost equals to the normal MCE) below the TN which results from metamagenitic transition under magnetic field. Considering of the normal and inverse MCE, DyNiSi2 compound also has potential applications in low-temperature multistage refrigeration.
Highlights
The magnetocaloric effect (MCE), a kind of physical phenomenon found more than 130 years ago, is one of the intrinsic properties of magnetic materials
The magnetic refrigeration (MR) based on MCE is becoming competitive with conventional gas compression/expansion technology because its environmental friendliness and high efficiency.[1,2,3,4,5]
MCE materials are generally evaluated by the following parameters: the maximum value of magnetic entropy change ((∆SM )max), the full width at half maximum of ∆SM − T curve, refrigerant capacity (RC) and adiabatic temperature change (∆Tad)
Summary
The magnetocaloric effect (MCE), a kind of physical phenomenon found more than 130 years ago, is one of the intrinsic properties of magnetic materials. Commercial and residential refrigeration, based on conventional gas compression/expansion technology, is a mature industry. The magnetic refrigeration (MR) based on MCE is becoming competitive with conventional gas compression/expansion technology because its environmental friendliness and high efficiency.[1,2,3,4,5] In the last twenty years great progress has been made on exploring large MCE materials for applications at room temperature such as refrigerators and air conditioners.[6,7] The typical room temperature MCE materials mainly include Gd5Si2Ge2,8,9 La(Fe, Si)[13,10,11,12,13,14] MnAs1-xSbx,[15] MnFeP1-xAsx,[16] Heusler alloys,[17,18] etc. Much attention has been paid on the MCE materials with low transition temperature because these materials are promising to be used for gas liquefaction in magnetic cooling cycle or combined magnetic-gas cooling cycle.[6,21] These low temperature MCE materials mainly include the rare earth based intermetallic compounds such as RCo2,22,23 RNi,[24] etc
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