Acoustic soft modes of Nb3Sn in high magnetic fields

Abstract In single crystal Nb3Sn the effect of a magnetic field upon the soft sound velocity vs (110, 1 1 0) was measured at different temperatures above the structural phase transition point. The observed quadratic variation with field is in accordance with theory. But the magnitude of the field dependence is much smaller than expected and can only be explained by existing theories if the magnetic moment of the electron would vary by as much as a factor of two within an energy interval of some 100 K.