Electric Conductivity and Resistance of Crystal Nickel

Magneto - resistance Curves for Single Crystals of Nickel.

S. Kay a found that with single crystals of nickel the longitudinal effect in every direction of the axes - tetragonal, diagonal, and trigonal - increases the resistance, and in the decreasing order (111), (110), and (100). The transverse effect gives an increase or decrease in the resistance according to the direction of the magnetic field. There is an increase with (001), and a decrease with (110) and (111). According to W. L. Webster, there is an effect with the (100) and (110) directions exactly similar to what has been found for iron (q.v.) for the magnetically corresponding directions, Fig.; but there is, in addition, a very large effect in the direction of easiest magnetization both for longitudinal and transverse phenomena. The curve for the (111) direction, where the change of resistance occurs within 5 per cent, of saturation, may be due to the acquisition, near the region of saturation, of uniformity and continuity in the magnetic direction of the crystals. This explanation involves a decrease in the resistance and not the increase actually observed.. W. L. Webster continued: In the case of the transverse phenomenon, there is also a change of resistance with magnetization along the (111) axis, but in this case it is a decrease in resistance. This suggests that both the changes that were found for this direction are akin to the changes of length in the direction of easiest magnetization that occur in nickel and iron. That is, they are due to the electrical anisotropy of nickel magnetized along its magnetic axis. If this be so, then the appearance of the curve, which is not at all what would be expected on such a view, must be due to comparatively large errors in the magnetization scale - errors particularly likely to occur for the direction of easiest magnetization. The fact that the anisotropy occurs only in nickel and not in iron must be connected with the difference in the relation between the magnetic and crystallographic axes in the two metals. In the case of iron the two sets coincide, and both have the simplest symmetry possible, whereas in nickel there are four magnetic axes which do not possess the simple symmetry of the crystal structure of this metal. There may be a further cause in that in iron there are approximately three magnetic electrons per atom, all of which have not yet been shown to have that relation to conductivity which was found for the single magnetic electron of nickel. Anomalies in the resistance of nickel in a magnetic field reported by F. Vilbig, were found by O. Stierstadt to be the result of errors mainly arising from incomplete demagnetization.

The Effect of Longitudinal (dotted) and Transverse (continuous) Fields on the Resistance for Nickel.

H. H. Potter measured the change of resistance of a nickel wire with transverse and longitudinal magnetization, and a selection of these results at different temp, is summarized in Fig. The dotted curves refer to the field parallel to the current, and the continuous curves to a field perpendicular to the current. In the neighbourhood of the Curie point, the change of resistance is independent of the field, and varies with the field and temp, in a way analogous to the variation of the magneto-caloric effect - Fig.