Suppression of first-order transition and large magnetocaloric effect in Mn_50-xNi₄₀In_10+x

Magnetic materials exhibiting large entropy change at the second-order phase transition (SOPT) near room temperature have attracted much attention because these materials are free from magnetic and thermal hysteresis, and may show large cooling efficiency. We have investigated Mn_50-xNi₄₀In_10+x alloys prepared by arc melting and vacuum annealing. The x-ray diffraction patterns analyzed using the Rietveld method shows that the samples crystallized in the cubic structure at room temperature. The thermomagnetic curves M(T) measured at μ₀H = 0.1T show that the first-order phase transition observed in the parent compound Mn_50-xNi₄₀In_10+x (x = 0) can be completely suppressed when x reaches 6. We observed large values of peak magnetic entropy change (ΔS_M,max) and relative cooling power (RCP) measured at 3 T for Mn₄₄Ni₄₀In₁₆ at 320 K. The measured values of ΔS_M,max and RCP are comparable to those of other Gd-free compounds showing magnetocaloric effect due to SOPT near room temperature. This suggests that the Mn_50-xNi₄₀In_10+x alloys have potential for room temperature magnetic refrigeration.