VII. On the richardson gyro-magnetic effect

Abstract

On the assumption that the molecular magnets in a ferro-magnetic substance consist of revolving electric charges associated with inertia, and that a change in any direction of the magnetisation of such a substance consequently implies the appearance in that direction of angular momentum which was not previously there, it is to be expected, as O. W. Richardson pointed out in 1908, that this change will also be accompanied by an angular impulse of reaction of which the magnitude is therefore equal and opposite to that of the corresponding angular momentum of the revolving charges. Such an impulse has now been observed by several experimenters. It is situated in the magnetic substance itself, and its sign points to the rotation of negative electricity as its cause. Richardson showed further that if the revolving charges are of one sign only, m and e representing their masses and charges respectively, the ratio of the angular momentum to the corresponding change in magnetic moment (M) is given by the equation angular momentum/M = 2 m / e .