Martensitic transformation and magnetocaloric effect of Cr-doped Mn–Ni–Fe–Ti all-d-metal Heusler alloys near room temperature

Abstract

Since the discovery of all-d-metal Heusler alloys, Ni–Co–Mn–Ti quaternary alloys have been widely studied and reported, but there are few studies on Mn-rich Mn–Ni–Ti all-d-metal Heusler alloys. In the present work, the structure, martensitic transformation, and magnetocaloric properties of the Mn50-xCrxNi36Fe4Ti10 (x = 1, 2, and 3) alloys were investigated. The behavior of the alloys during martensitic transformation accompanied by thermal hysteresis indicates the nature of first-order structural transformation, and the doping of Cr results in the transition temperature closer to the room temperature. Martensitic transformation temperature decreases from 309 K to 288 K with increasing Cr content. For this system, the inverse of the magnetic susceptibility follows the Curie-Weiss law, and the Curie paramagnetic temperatures (TCW) obtained by fitting in the high-temperature paramagnetic region are 170 K (x = 1), 119 K (x = 2), and 116 K (x = 3), respectively. The contribution of the magnetic entropy change to the total entropy is not large because of the paramagnetic nature of the alloys. The magnetic entropy changes ΔSm of the alloys are 0.58 Jkg−1K−1 (x = 1), 0.72 Jkg−1K−1 (x = 2), and 0.29 Jkg−1K−1 (x = 3) at room temperature under 5 T magnetic field.