Magnetocaloric Effect in Ni0.5Mn_0.5- xSnₓ Alloys

We have studied the magnetic properties and magnetocaloric effect in bulk Ni0.5Mn0.5-xSnxalloys (x = 0.2 and 0.3) prepared by arc-melting. Experimental results reveal that with increasing Sn content the ferromagnetic order slightly decreases, but the Curie temperature (TC) increases from 333 K (for x = 0.2) to about 354 K (for x - 0.3). Based on magnetic-field dependences of magnetization (M - H curves) recorded at various temperatures, ΔSM(T) curves of the samples under an applied field interval of 0-12.0 kOe were obtained. Maximum ΔSMvalues achieved around TCare about 1.2 and 1.1 J.kg-1.K-1for x = 0.2 and 0.3, respectively. Detailed analyses of M - H curves in the vicinity of TC, used the Arrott-Noakes method, reveal the samples undergoing the second-order phase transition with the critical exponents of β = 0.503 ± 0.021 and γ = 1.246 ± 0.013 for x = 0.2, and of β = 0.426 ± 0.016 and 7 = 1.232 ± 0.014 for x = 0.3. The difference in value of the exponents together with x-ray diffraction data will be used to explain the magnetic properties and magnetocaloric effect in Ni0.5Mn0.5-xSnx.