Abstract:
The effect of Ge substitution on the magnetic, magnetocaloric, and exchange bias properties of
Heusler alloy system Ni50Mn36Sn14-xGex (x ¼ 1, 2) has been investigated. With the increase of
Ge content, the cell volume decreases due to the smaller Ge radius and the martensitic transition
temperature increases, while the Curie temperature of the austenite phase shows a small decrease.
Metamagnetic behavior is observed in the low temperature magnetization isotherms for x ¼ 1,
whereas it is less pronounced in x ¼ 2. The maximum magnetic entropy changes associated with
the martensitic transition are 7.8 J/kg K and 2.3 J/kg K for x ¼ 1 and 2, respectively, for a field
change of 5 T. Relative cooling power is found to be more in the vicinity of the Curie
temperature of the austenite phase, compared to that at the martensitic transition temperature in
both x ¼ 1 and 2. At low temperatures, both the samples exhibit exchange bias effect, with x ¼ 2
showing higher value of exchange bias field. This is ascribed to the coexistence of ferromagnetic
and antiferromagnetic interactions in these alloys. Further, the critical behavior of the austenite
phase of both the alloys is studied and the values of the critical exponents are found to be
different from the mean field values, which is attributed to the magnetic inhomogeneity
originated due to Ge substitution.
