The influence of a magnetic field on dislocation depinning from paramagnetic obstacles is studied. It is suggested that the depinning may take place due to the following mechanism. When a kink passes an obstacle the unsaturated electron bonds of the kink and the obstacle form a radical pair. Magnetic field-induced intercombination transitions from the binding to an antibinding state of the radical pair lead to an additional population of high spin antibinding states with lower binding energy. This results in a plasticity growth. A strong dependence of the amplitude-dependent internal friction of dislocations on the magnetic field is predicted.

• Received 2 April 1996

DOI:https://doi.org/10.1103/PhysRevLett.78.2779