  The irreversibility of the martensite transition in magnetic shape memory
alloys (MSMAs) with respect to external magnetic field is one of the biggest
challenges that limits their application as giant caloric materials. This
transition is a magneto-structural transition that is accompanied with a steep
drop in magnetization (i.e., 'delta M') around the martensite start temperature
(Ms) due to the lower magnetization of the martensite phase. In this
communication, we show that 'delta M' around Ms in Mn rich Ni-Mn based MSMAs
gets suppressed by two orders of magnitude in crushed powders due to the
stabilization of the martensite phase at temperatures well above the Ms and the
austenite finish (Af) temperatures due to residual stresses. Analysis of the
intensities and the FWHM of the x-ray powder diffraction patterns reveals
stabilized martensite phase fractions as 97, 75 and 90% with corresponding
residual microstrains as 5.4, 5.6 and 3% in crushed powders of the three
different Mn rich Ni-Mn alloys, namely, Mn1.8Ni1.8In0.4, Mn1.75Ni1.25Ga and
Mn1.9Ni1.1Ga, respectively. Even after annealing at 773 K, the residual stress
stabilised martensite phase does not fully revert to the equilibrium cubic
austenite phase as the magneto-structural transition is only partially restored
with reduced value of 'delta M'. Our results have very significant bearing on
application of such alloys as inverse magnetocaloric and barocaloric materials.
