Study of magnetostriction and magnetoresistance in nickel based metallic glasses

Abstract

Metallic glass ribbons ofNi-Fe-B alloys are prepared by melt spinning technique. with composition Nigo_xFexBlowhere x=20,30,40 and 50. The thicknesses of the samples were 22f.Lm,20f.Lm,23f.Lmand 19f.Lmrespectively. The amorphousity of the samples has been checked by X-ray diffraction technique. Magnetostriction of these ribbons has been measured by resistance strain gauge technique at room temperature as a function of field and composition. The linear saturation magnetostriction of the ribbons has been determined by rotating the magnetization vector from perpendicular position to parallel position of the magnetization direction with respect to the direction of strain measurement. It is assumed that the direction of the field and the direction of magnetization practically coincides, specially for the maximum field. The direction of measurement of strain is determined from the direction of the bonded strain gauge. The magnetostrictive in amorphous alloys originate from the magneto elastic interaction associated with the local anisotropies and the local strain controlling the local direction of the magnetic moments. The saturation magneto stricti on decreases as Ni-concentration increases. The magnetoelastic energy and hence magnetostriction depends on the electrons located at the Fermi level of the alloy and is proportional to the spin-orbit energy shift at the Fermi-level. However, the observed magnetostriction has been discussed in terms of the pair model with random local axis because of the simplicity of the model. The results are interpreted in terms of domain motion and domain rotation which are spontaneously strained. Hall resistivity of amorphous Ni-Fe-B ribbons has been measured as a function Of field and change of composition. The field was varied from 0 to 4.16 KG and the composition of the ribbons was varied from 20% to 50% Fe ke,~ping the boron - concentration of 20% as constant. In the range of the field available Hall resistivity increases for all the compositions with increasing field, because the saturation field needed for attaining the maximum Hall resistivity could not be reached. The results are explained by the conventional theory.