Abstract
In this work, ribbons of composition Ni50-x Co (x) Mn38Sn12 (x = 1, 2, and 3 at%.) were produced by the melt-spinning technique. Martensitic transformation shifts to lower temperatures with increasing (a) concentration of Co or (b) the external magnetic field. Structure at room temperature of alloys with x = 1 and x = 2 is martensite (monoclinic with a 10 M modulation), whereas for the alloy with x = 3 is austenitic. The temperature shift directly reports the valence electrons concentration per atom e/a of alloys.