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

Large magnetoresistance effects were observed in Ni50Mn50−xSnx Heusler alloys for concentrations 13⩽x⩽16. 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 (Δρ/ρo) were −42% for x=14 at T≈250 K, and −23% above room temperature (T≈320 K) for the sample with x=13, where the magnetic field change was ΔH=5 T. Magnetization and X-ray diffraction measurements indicate that the origin of the observed magnetoresistance is a magnetically induced magnetostructural transition from a complex 10 M modulated orthorhombic phase containing some antiferromagnetic coupling to a ferromagnetic cubic L21 structure.