Magnetocaloric effect in ScGdTbDyHo high-entropy alloy: Impact of synthesis route

SA Uporov and SK Estemirova and EV Sterkhov and IA Balyakin and AA Rempel, INTERMETALLICS, 151, 107678 (2022).

DOI: 10.1016/j.intermet.2022.107678

Magnetic energy conversion systems based on magnetocaloric effect promise to be an efficient and eco-friendly alternative to widespread gas cooling systems. Progress in this field initiates an active search for high-performance magnetic refrigerants with suitable characteristics. Among various caloric materials, rare-earth multi- principal element alloys are of particular interest to achieve these purposes. Since structure and proper-ties in these materials strongly depend on synthesis conditions and fabrication prehistory, these issues need to be considered for each multi-element systems. This study is aimed to address structure formation, magnetic and magnetocaloric properties in ScGdTbDyHo high-entropy alloy fabricated under different conditions. We analyze the liquid and solid phases in this system using the ab initio molecular dynamics simulations and find that the alloy has a strong tendency to form a single-phase solid solution. Within the experimental study, as-cast, rapidly quenched, thermally annealed and severely cold-deformed alloy samples have been examined. We have found that all the fabricated specimens are single-phase hexagonal close- packed solid solutions characterized by different density of structural defects. The magnetic measurements reveal a complex magnetic structure in these materials. The Neel point in the studied alloys varies in the range of 139-144 K. A field-induced metamagnetic transition from antiferromagnetic to ferromagnetic state is observed in the alloy samples at all temperatures below the Neel point. In the magnetically ordered state, all the materials demonstrate large coercive force, reaching 4 kOe. Despite of the magnetic hysteresis, the alloys demonstrate the largest values of relative cooling power (920-984 J/kg at 5 T magnetic field) among similar rare-earth high-entropy systems reported so far. Analysis of the experimental results obtained for the alloy samples fabricated under different synthesis conditions allows us to conclude that there is a correlation between structural defectiveness and refrigerant capacity in this rare-earth system.

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