On the relation between thermally activated and magnetically stimulated processes during dislocation movement in InSb crystals in a magnetic field

Abstract

It is shown that, in contrast to conventional mobility of dislocations in InSb crystals, which is characterized by a thermally activated temperature dependence of velocity (v ∝ exp(-U/kT), where U is the activation energy), relaxation displacements of dislocation in the same crystals in a magnetic field in the absence of external load are described by a more complex temperature dependence. The V(T) dependence in the temperature range 120–250°C studied here exhibits a tendency to linearization in the ln v vs. 1/T coordinates only in its low-temperature part and rapidly attains saturation upon an increase in temperature. The observed decrease in the thermal sensitivity of relaxation mobility of dislocations in the magnetic field upon heating is interpreted in the framework of the model describing the detachment of a dislocation from a point defect as a sequence of two processes: (i) magnetically stimulated lowering of the barrier, U → U′ (over time τ_sp of the spin evolution in the system) and (ii) expectation of thermal fluctuation (over a time τ_th ∝ exp(U′/kT)). Thus, at low temperatures, we have

, and the total time before detachment amounts to τ_th + τ_sp ≈ τ_th. On the contrary, at high temperatures, we have

, and τ_th + τ_sp ≈ τ_sp (i.e., the motion becomes athermal). It is shown that this model correctly describes the results of measurements and makes it possible to separate the effects. In particular, it is found that the barrier height decreases from the activation energy U = 0.8 eV under a load of 10 MPa to U′ = 0.25 eV in a magnetic field of B = 0.8 T.