Vibrating reed study of a magnetically reversible region in Nb and NbSe2

Vibrating reed measurements of the flexural resonances of thin cantilevered Nb foils and NbSe 2 single crystals reveal extended regions of temperature T and magnetic field H for reversible flux line (FL) motion. The peak temperature ('irreversibility line') of the reciprocal quality factor 1/Q is found to be independent of frequency for 5*10 2 <f<5*10 4 Hz, implying that the time scale of FL pinning is extremely T- and H-dependent. Extended regions of magnetic reversibility are therefore not restricted to high-T c or extremely anisotropic materials, and depend upon sample orientation with respect to the applied field.