Abstract: We report the study of structural and magnetic properties of Ni 50Mn 50 - xSn x(x = 11 and 12.5) and Ni 49Mn 51 - xSn x(x = 13) Heusler alloys in bulk and ribbon shape. Experimental results were obtained by differential scanning calorymetry, X-ray diffraction, and vibrating sample magnetometry techniques. The Ni-Mn-Sn system undergoes a martensitic structural transformation in a wide temperature range. For example, for Ni 49Mn 38Sn 13, the start and finish temperatures of the martensitic phase transformation for bulk alloy were M-s = 288 K and M-f = 245 K, while the ones found for austenite were A-s = 261 K and A-f = 304 K. The Curie temperature for the austenite was evaluated to be around 325 K. In the ribbon of same composition, the magnetization increases monotonically with the temperature showing an abrupt change in the slope at T = 258 K as a consequence of the martensite-austenite transformation. The complex behavior exhibited by these Heusler alloys should be ascribed to the strong coupling between magnetism and structure, being their magnetic behavior determined by the distance between Mn atoms.

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