  A magnetic field relaxation at the center of a pulse-magnetized single-domain
Y-Ba-Cu-O superconductor at 78K has been studied. In case of a weak
magnetization, the magnetic flux density increases logarithmically and
normalized relaxation rate defined as S=-d(lnB)/d(lnt) is negative (S=-0.037).
When an external magnetic field magnitude increases, the relaxation rate first
decreases in absolute value, then changes sign (becomes positive, S>0) and
after reaching some maximum finally reduces to a very small value.
Non-monotonous dependence of S vs Ha is explained by a non-homogeneous local
temperature distribution during a pulse magnetization.
