Observation of exchange-bias in the inverse Heusler alloy Mn1.5Ru1.5Si

Abstract

Recently, Mn-Ru-Ga based inverse Heusler alloys have been found to be potential candidates for half-metallic fully compensated ferrimagnetic materials. In this work, we have studied another Heusler based alloy, Mn1:5Ru1:5Si, intending to design a compensated ferrimagnet. The alloy Mn1:5Ru1:5Si crystallizes in an inverse Heusler (XA) structure with a small amount of anti-site disorder. Our magnetic study indicates that the alloy orders magnetically below about TN = 50 K, which is characterized by a sharp drop in magnetization. Nevertheless, the isothermal magnetization curve shows a tendency of saturation and finite coercivity at 5 K, which rules out a pure antiferromagnetic state. Interestingly, Mn1:5Ru1:5Si shows vanishingly small magnetic moment, which also rules out possibility of a pure antiferromagnetic state. The alloy shows a significant amount of exchange-bias at low temperature. The alloy fails to obey a Curie-Weiss law between 300 and 50 K, indicating short-range correlations prior to the long-range order at TN. The exchange bias possible arises from the interfacial coupling of the short range ferromagnetic clusters with the long range antiferromagnetic state. The observation of exchange bias for such a system along with a low net magnetization value, has immense potential for magneto-electric applications and switching devices. The resistivity versus temperature data of the sample indicates a metallic character, albeit with a rather large value resistivity. The resistivity data show an upturn below 25 K that follows a logarithmic behaviour. Such upturn may be due to weak localization effect due to the presence of antisite disorder and short range magnetic clusters.