Electrical Resistance of Nickel and Permalloy Wires as Affected by Longitudinal Magnetization and Tension

The changes in the electrical resistance of ferromagnetic metals in magnetic fields and under mechanical stresses are abnormal in comparison with such changes in non-ferromagnetic metals. Published results for nickel and nickel-rich alloys, reviewed in detail, show wider diversity than can be ascribed to accident. A full bibliography is included.Simple cases of these magneto-resistance and elasto-resistance effects have been studied in permalloys containing from 45 to 90 percent nickel. The results of two series of experiments, in 1923 and 1929, are presented, and show that both effects have, in these ferromagnetic alloys, the same origin. This common origin can be considered as the orientation, by one means or the other, of atomic magnetic axes associated in each atom with mechanical asymmetry.The connection between these resistance effects and magnetostriction is emphasized. Conclusions are drawn as to the kinds of re-orientation involved in magnetizing and as to the relative importance in the observable effects of intra-atomic and interatomic magnetic fields. Questions for further experiment are raised.