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 (T-M), which can be tuned in temperature through variations in Sn concentration. The largest observed values of the magnetoresistance (Delta rho/rho(o)) were -42% for x = 14 at T approximate to 250 K, and -23% above room temperature (T approximate to 320 K) for the sample with x = 13, where the magnetic field change was Delta H=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 L2(1) structure. (C) 2007 Elsevier B.V. All rights reserved.