Structural Phase Transition and Magnetic Properties in Mn2−xCuxSnS4 (x = 0, 0.05, 0.1, 0.6, 0.7): From Defect Rock Salt to Disordered Spinel

Orthorhombic Mn₂SnS₄ with defect-ordered rock salt structure exhibits complex magnetic properties with two magnetic transitions, antiferromagnetism at around 152 K and a weak ferromagnetism at 53 K. In this article, we have studied the effect of copper(I) substitution on the structure and magnetic properties of Mn_2−xCu_xSnS₄. A structural phase transition from orthorhombic defect-ordered rock salt structure, Cmmm (for x = 0.05 and 0.1) to cubic spinel structure, Fd−3m (x = 0.6 and 0.7) is observed with Cu substitution in Mn_2−xCu_xSnS₄. In the defect-ordered rock salt structure, Cu goes to the octahedral Mn site, while in the spinel structure, Cu along with Mn goes to tetrahedral voids. With initial Cu(I) substitution in the orthorhombic phase, the low-temperature weak ferromagnetic ordering temperature increases from 53 K to about ∼140 K and ∼120 K for x = 0.05 and 0.1, respectively, while the high-temperature antiferromagnetic ordering temperature remains invariant. Higher amount of Cu substitution in Mn_2−xCu_xSnS₄ leads to structural transformation of orthorhombic to a cubic spinel phase (0.6 ≤ x ≤ 0.7), in which the magnetic ions occupy both tetrahedral and octahedral voids in a disordered manner resulting in further lowering of magnetic ordering temperature.