Influence of Si substitution on the structure, magnetism, exchange bias and negative magnetoresistance in Ni48Mn39Sn13 Heusler alloys

The effect of partial Si substitution for Sn on the structure, magnetism, magnetic entropy change, exchange bias and negative magnetoresistance in Ni48Mn39Sn13-x Si x(1 <= x <= 4) Heusler alloy systems is investigated. A small amount of Si in the Sn position influences the characteristic transition temperatures and the magnetocaloric effect. A maximum positive entropy change of 5.13 J kg(-1) K-1 is observed for a field change of 9 T in the x = 1 alloy. An increase in Si content increases the exchange bias field. The exchange bias field and the coercive field strongly depend on the Si content. For the x = 4 alloy, an exchange bias field of 354 Oe is observed. In addition, a negative magnetoresistance is observed in this alloy system, which decreases with Si content. The increase in resistivity at the martensitic transition could be attributed to the formation of superzone boundary gaps that changes the density of states near the Fermi surface.