Suppression of magnetic relaxation processes in hard superconductors by   a transverse AC magnetic field
  The effect of the transverse AC magnetic field on relaxation process in YBa$_2$Cu$_3$O$_x$ melt-textured superconductor was studied. A factor of 50 suppression of the relaxation rate could be achieved at the expense of some reduction in the maximum trapped field, with the magnetic-induction gradient being unchanged. This phenomenon is interpreted as a result of an increase of the pinning force after the action of the transverse AC magnetic field. 
L. M. Fisher, A. V. Kalinov, I. F. Voloshin, V. A. Yampol'skii