The Influence of Multiple Magnetic Ordering on the Magnetocaloric Effect in RNiAl Alloys
Both the change in magnetic entropy (ΔSmag) and the adiabatic temperature rise (ΔTad) induced by a change of magnetic field were determined for a series of (Gd1-xErx)NiAl alloys (where x = 0, 0.30, 0.46, 0.60, 0.80 and 1.00). Through magnetic and heat capacity measurements, these materials were found to possess multiple antiferromagnetic and ferromagnetic ordering processes. The value of ΔSmag was observed to peak around the antiferromagnetic transition temperature for ErNiAl, with the maximum gradually broadening and shifting upward toward the Curie temperature as the Gd content is increased. For Gd-rich alloys, a significant contribution to the magnetic entropy change is observed at both the low and high-temperature transitions, resulting in a skewed caret-like ΔSmag vs. temperature profile. Broad zero-field transitions coupled with opposing shifts in entropy around the ferromagnetic and antiferromagnetic ordering temperatures induced by the application of a magnetic field are believed to contribute to this effect.
KeywordsMagnetocaloric Effect Magnetic Entropy Change Heat Capacity Measurement Refrigeration Cycle Magnetic Refrigeration
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