EFFECTS OF MAGNETIC-FIELDS ON THE DISLOCATION UNLOCKING FROM PARAMAGNETIC CENTERS IN NONMAGNETIC CRYSTALS

Displacements of dislocations as a result of exposing the specimens to a static magnetic field (B = 0.1-2 T) in the absence of mechanical lo ading in the temperature interval T= 4.2-293 K were found and investig ated for NaCl, CsI, LiF, Zn and Al single crystals. This effect is cha racterized by the following properties: the mean dislocation path lBAR increases linearly with the time t of the magnetic treatment; the mea n dislocation velocity v is proportional to the square of the magnetic magnetic induction (v is-proportional-to B2) and inversely proportion al to the square root of the concentration of paramagnetic impurities (v is-proportional-to 1/square-root C); the effect is temperature inde pendent in the range T = 4.2-77 K and it grows only by 20%-30% with a further increase in T up to room temperature; l(t) and l(B) saturate a t large values of t and B at a level corresponding to an average dista nce between ''forest'' dislocations; an abrupt decrease in the effect is found when the frequency nu of an alternating magnetic field exceed s some critical value nu(c) is-proportional-to B2 (nu(c) almost-equal- to 15 Hz at B = 0.3 T). The phenomenon is interpreted as a result of u nlocking of dislocations from paramagnetic centers under the action of an external magnetic field and motion of dislocations in the long-ran ge internal stress field.