Anisotropic electrical resistance in Ni 76Mn 24 and Ni 74Mn 24Pt 2 amorphous alloys

Abstract

Magnetoresistance measurements have been carried out on the amorphous Ni 76Mn 24 and Ni 76Mn 24Pt 2 thin film alloys at T = 4.2, 77 and 300 K for three different cases: (i) The applied magnetic field H parallel to the current J (longitudinal magnetoresistance); (ii) the applied field perpendicular to the current, but parallel to the film surface (Transverse magnetoresistance); (iii) the applied field perpendicular to the film surface (Normal magnetoresistance). The resistivity for H ⊥ J in a saturating magnetic field (the field H = 20 kOe is large enough to eliminate teh magneoresistance effec) has been observed to be dependent upon the direction of the field relative to the easy axis ( z-axis) along which the magnetic anisotropy has been developed as being uniazxial in character. It was determined that the resistance anisotropy exhibits the same symmetry as the uniaxial magnetic anisotropy. The relationship between the magnetic anisotrop and the ferromagnetic anisotropy in resistivity is discussed. Furthermore, replacing some Ni atoms with Pt impurities has been observed to result in a decrease of ferromagnetic anisotropy in the resistivity. Some possible reasons for this are discussed as well.