Tunable magnetostructural coupling and large magnetocaloric effect in Mn1−xNi1−xFe2xSi1−xGax

A common method of realizing a magnetostructural coupling for MnNiSi is chemically alloying it with a ternary compound possessing a stable Ni2In-type structure. In this way, the substituting elements and levels are determined by the stoichiometry of counterpart compounds. In this work, chemical co-substitutions of Fe and Ga at three different atomic sites of MnNiSi were performed. The selections of substitution elements and levels were based on the site occupation rule and an analysis of the site-dependent substitutional effects on structural stability, Curie temperatures, and magnetic moment of MnNiSi. A broad Curie temperatures window of 285 K spanning room temperature was established in Mn1−xNi1−xFe2xSi1−xGax. Strong magnetostructural transformations with large magnetization difference were realized in this window. A relatively large magnetic entropy change of −38.1 J/kg K was observed for a field change of 5 T near room temperature in the alloy with x = 0.15.