Magnetic interactions in the martensitic phase of Mn rich Ni-Mn-In shape memory alloys

Abstract

The magnetic properties of Mn2Ni(1+x)In(1−x) (x = 0.5, 0.6, 0.7) and Mn(2−y)Ni(1.6+y)In0.4 (y = −0.08, −0.04, 0.04, 0.08) shape memory alloys have been studied. Magnetic interactions in the martensitic phase of these alloys are found to be quite similar to those in Ni2Mn(1+x)In(1−x) type alloys. Doping of Ni for In not only induces martensitic instability in Mn2NiIn type alloys but also affects magnetic properties due to a site occupancy disorder. Excess Ni preferentially occupies X sites forcing Mn to the Z sites of X2YZ Heusler composition resulting in a transition from ferromagnetic ground state to a state dominated by ferromagnetic Mn(Y)-Mn(Y) and antiferromagnetic Mn(Y)-Mn(Z) interactions. These changes in magnetic ground state manifest themselves in observation of exchange bias effect even in zero field cooled condition and virgin magnetization curve lying outside the hysteresis loop.