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Origin of giant magnetoresistance across the martensitic transformation for Ni44Cu2Mn43In11 alloy: Formation of phase fraction

We have studied the phase volume fraction related magnetoresistance (MR) across the first order martensite transformation (MT) of Ni44Cu2Mn43In11 alloy. Within the metastability of MT, an isothermal application of magnetic field converts the martensite into austenite. The field induced austenite phase fraction (fIA) at any temperature depends on the availability and instability of martensite phase fraction (fM ) at that temperature. This fIA is found to contribute most significantly to the observed giant MR while the contribution from pure martensite and austenite phase fraction is negligible. It is found that the net MR follows a non linear proportional relation with the fIA and the ascending and descending branch of fIA follows different power law giving rise to hysteresis in MR. Here we present a detail explanation of the observed behaviours of MR based on the existing phase fraction.