Magnetic and magnetocaloric properties of Ni-Ag-Mn-Sn ribbons and their composites

Abstract

In this work, we have investigated the influence of Ag-doping on the magnetic and magnetocaloric effect (MCE) of Ni50-xAgxMn37Sn13 ribbons with x = 1, 2, and 4, which were prepared by a melt-spinning method. With increasing Ag concentration, a systematic decrease in the antiferromagnetic interaction and in the magnetic phase transition temperatures was observed. Analyses of the critical behavior based on the Banerjee criterion and scaling hypothesis for M(H, T) data near the ferromagnetic-paramagnetic transformation prove an increase of Ag favors establishing long-range ferromagnetic interactions in the austenitic phase. The temperature and magnetic field dependences of magnetic entropy change, ΔSm(T, H) were investigated via isothermal magnetization measurements. Interestingly, these samples exhibit a MCE at room-temperature with the ΔSm(T) curves distributed over a quite wide temperature range. To enhance the relative cooling power (RCP) value and to extend the magnetic phase transition region, we have prepared the composites in the form of the layered material samples based on ribbons obtained above. Under ΔH = 10 kOe, the maximum value of ΔSm (denoted as |ΔSmax|) at around room-temperature is 1.08 J kg−1 K−1, corresponding to RCP = 51.8 J kg−1, which is about 10% higher than that obtained from a separate sample. Additionally, we also pointed out that the dependences of |ΔSmax| on ΔH at around room-temperature for samples obey a power law, |ΔSmax| = a × ΔHn, and all the ΔSm(T, H) data obey completely a universal master curve.