The Hall effect has been studied in three permalloys, the composition being 84, 81 and 78 percent nickel with the remaining part iron. The observed transverse electromotive forces are unsymmetrical for the two opposite directions of the magnetic field. This dissymmetry arises from an unsymmetrical change of resistance in the transverse magnetic field. Since this change of resistance is a complex function of the magnetic field, this dissymmetry is also a complex function of the magnetic field. In each of these alloys the Hall effect is at first positive as in iron but reverses its direction and becomes negative as in nickel for sufficiently large magnetic fields. For magnetic fields less than about 11,000 gauss an increase in the concentration of iron increases the Hall effect. With an increase in the concentration of iron the maximum in the curve showing the Hall electromotive force as a function of the magnetic field shifts toward greater magnetic fields. The greater the concentration of iron, the larger is the magnetic field at which a reversal in the direction of the Hall electromotive force takes place.

Each of the Hall effect curves can be resolved into two component curves, one negative, the other positive. The negative component is a straight line, with a slope which is nearly the same for each alloy. This negative component may be attributed to the action of the magnetic field on the so-called free electrons. The positive component has the form of the corresponding curve for iron or nickel. The magnitude of this component increases with an increase in the concentration of the iron. The positive component may be attributed to the orientation of the elementary magnets by the transverse magnetic field.

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