The influence of thermal activation and the intrinsic temperature dependence of the spin torque effect in current-induced domain wall motion

An experimental study of domain wall motion in Ni 80 Fe 20 ring structures induced by current pulses as well as conventional magnetic fields is presented. Using constrictions we demonstrate that current-induced domain wall motion can be used to displace walls into parts of the structure where no pulsed currents are flowing. Measurements at variable temperatures between 2 and 300 K show that the fields necessary for wall motion decrease with increasing temperature, which can be explained by thermal activation. For the current-induced case we find, depending on the geometry and temperature range, that the current densities necessary for displacement can increase or decrease with rising temperature. This indicates that, in addition to thermal excitations, an intrinsic temperature dependence of the efficiency of the spin torque effect is present and leads to an increase in the critical current density with increasing temperature.