  The effect of Si and Ga substitutions on the magnetic and the magnetocaloric
properties in Heusler based system Ni46Co4Mn38Sb12-xZx (Z=Si and Ga) has been
studied. From the M(T) plots it is found that Si substitution stabilizes the
austenite phase, whereas, Ga substitution stabilizes the martensite phase.
Strong metamagnetic behaviour is observed in the M(H) isotherms for Si=0.75 and
1, whereas, such a behaviour is absent in the Ga substituted alloys. Associated
with magneto-structural transition, large MCE of 58 J/kg K and 70 J/kg K is
observed for x=0.75 and 1, respectively in the case of Si. Though the MCE
observed in x=0.5 and 1 in the case of Ga is much lower, the MCE peak is found
to be quite broad.
