Emergence of compensated ferrimagnetic state in Mn2-xRu1+xGa (x = 0.2, 0.5) alloys

Abstract Mn2RuGa is known to be a ferrimagnetic compound below 460 K, while Ru2MnGa is an antiferromagnet with Neel temperature as low as 15 K. In the present work, we have studied the solid solutions of these two compositions, namely Mn 2 - x Ru 1 + x Ga (x = 0.2, 0.5), intending to design a fully compensated ferrimagnet. We successfully synthesized the compositions which crystallize with an inverse Heusler (XA) structure. The magnetic transition temperatures of both the alloys are found to be just above room temperature, and the magnetization data indicate a ferrimagnetic ordering. The compositions show spin glass like state at low temperature, which possibly emerges from the disorder and random magnetic correlations due to doping. Most interestingly, the x = 0.5 alloy shows the vanishingly small moment at low temperature, which can be explained on the basis of antiparallel alignment of moments at two inequivalent sites of Mn. The composition also shows a significant amount of exchange bias at low temperature. The observation of exchange bias for a system with a low value of net magnetization is much preferred for magneto-electric applications. Interestingly, both the samples show a transition from a high-temperature semiconducting phase to a low-temperature metallic phase. The electrical transport in the high-temperature phase is found to be dominated by small polaron hopping.