The Hall Effect and the Nernst Effect in Magnetic Alloys

Hall Effect in Magnetic Alloys.—In the iron-copper series a maximum effect was obtained with 1.5 per cent. copper. The variation with composition is very similar to the variation of electric resistance. In the nickel-copper series the effect reaches a maximum with about 26 per cent. copper when the composition corresponds to the formula Cu${\mathrm{Ni}}_3$, and then drops suddenly to a small fraction of its maximum value. In the iron-nickel series, although the effect is positive for iron and negative for nickel, the effect increases linearly with the proportion of nickel added to iron until for 13 per cent. nickel it is six times as great as for pure iron. In certain alloys the variation of the effect with the field strength is anomalous, the effect being negative for weak fields and positive for strong ones. An explanation based on the theory of Borelius is suggested which assumes that in addition to the positive part of the effect which is proportional to the field strength there is a negative part which reaches a limiting value for strong fields.