Influence of Magnetic Field on Magnetostructural Transition in

A Mn-enriched Ni 46.4 Mn 32.8 Sn 20.8 Heusler alloy has been prepared by the induction melting and casting method. The samples used were annealed at 900oC during 72 h with a subsequent water quench. The magnetostructural transformation (MST) in the vicinity of T m=230K and T a=250K has been found, and characterized by DSC, magnetization and resistivity measurements. Changes in the crystal structure due to the MST were observed using neutron diffraction at different temperatures. The crystal structure of martensitic phase shows a good fits to the 4-layered orthorhombic martensite with a Pmma space group. The linear shift of transformation temperatures was found in the entire high magnetic field range up 14T to be dTm/dB0 = -1.50 K/T and dTa/dB0 = -1.26 K/T, whereas in the low field range we found an increase of both characteristic temperatures. The entropy changes at the MST were evaluated using the Clausius-Clapeyron relationship. The transformation-induced magnetoresistance has been measured.