The effects of the addition of Co on the magnetic anisotropy in Ni 55-xFe18Ga27Cox (x = 1-6) single-variant ferromagnetic shape memory alloys have been investigated. By the addition of Co from 1 to 6 at.%, the Curie temperature TC is increased from 318 to 405K, keeping the martensitic transformation temperatures above room temperature. As a result, the value of the uniaxial magnetic anisotropy constant |Ku| at 300K increases with increasing x of the Co concentration and the martensite phase of Ni49Fe 18Ga27Co6 exhibits a relatively high value of |Ku| = 1.15 × 105Jm-3 at 300K. With increasing Co concentration, on the other hand, the c axis changes from the magnetic easy axis to the hard axis at 4.2K, that is, the sign of Ku is reversed from positive to negative between 2 and 3at.% Co. Furthermore, Ku in Ni53Fe18Ga27Co2 is positive below 100K and negative above 100K up to TC, reducing the magnetic anisotropy around 200K. From the present results, it is evident that the magnetic anisotropy of Ni55-xFe18Ga 27Cox (x = 1-6) single-variant ferromagnetic shape memory alloys is very sensitive to Co concentration and also temperature.
ASJC Scopus subject areas