Effects of magnetic fields on the dislocation unlocking from paramagnetic centers in non-magnetic crystals

Abstract

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 loading in the temperature interval T=4.2–293 K were found and investigated for NaCl, CsI, LiF, Zn and Al single crystals. This effect is characterized by the following properties: the mean dislocation path l increases linearly with the time t of the magnetic treatment; the mean dislocation velocity v is proportional to the square of the magnetic magnetic induction (v∝ B2) and inversely proportional to the square root of the concentration of paramagnetic impurities (v∝ 1/√C); the effect is temperature independent 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 at large values of t and B at a level corresponding to an average distance between “forest” dislocations; an abrupt decrease in the effect is found when the frequency v of an alternating magnetic field exceeds some critical value vc ∝ B2 (vc ≈ 15 Hz at B = 0.3 T).