Note on a Variation with Frequency of the Torsional Modulus of German Silver Wire and its Relation to Gyromagnetic Measurements

A quite unmistakeable deficit of the mean gyromagnetic ratio for certain ferromagnetic substances as reported some years ago by W. Sucksmith and L. F. Bates from the mean ratio obtained for the same substances in much more elaborate investigations in the laboratories of one of us, might be explained by such a variation alone if the torsional modulus of German silver wire in rapid oscillation (dynamic modulus, $M_d$) were smaller by four or five percent than the modulus for steady twist (static modulus, $M_s$)—a result, however, which we should not expect to find. The calibrating operations of the authors referred to were carried out partly with rapid oscillations, partly with steady deflections; and they assumed (implicitly) that the two moduli were equal. We have not worked with the true static modulus, but have determined the ratio of $M_d$ for frequencies ranging approximately from 17 to 50 per second, comparable with those used in the work mentioned, to $M_d$ for periods ranging approximately from 4 sec. to 28 sec.—times doubtless quite comparable with or greater than the times required to produce steady twists in this work. We have detected no certain change of modulus in the high frequency range, or in the range of periods between 4 sec. and 28 sec. However, the modulus has been found to diminish by 1 percent in passing from oscillations with the period 5 sec. to those in the high frequency range. This unexpected diminution reduces somewhat the discrepancy that initiated the experiments described in this note, and it seems important to us for other reasons also. But much the greater part of the discrepancy must be accounted for in other ways.