  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.
