Magnetoresistance and field-induced structural transitions in Ni50Mn50−xSnx Heusler alloys

Large magnetoresistance effects were observed in Ni50Mn50-xSnx Heusler alloys for concentrations 13x16. The effects occur at the respective martensitic transition temperatures (TM), which can be tuned in temperature through variations in Sn concentration. The largest observed values of the magnetoresistance (Deltarho/rhoo) were -42% for x=14 at Tapprox 250K, and -23% above room temperature (Tapprox 320K) for the sample with x=13, where the magnetic field change was DeltaH=5T. Magnetization and X-ray diffraction measurements indicate that the origin of the observed magnetoresistance is a magnetically induced magnetostructural transition from a complex 10M modulated orthorhombic phase containing some antiferromagnetic coupling to a ferromagnetic cubic L21 structure.