Transformation of the Domain-Wall Structure in Permalloy Nanotape Under Electrical Current Pulses

Motion of the magnetic domain walls under the pulses of magnetic field or spin-polarized electric current is studied experimentally by direct visualization of the walls. The experiments are performed in the temperature range from 300 down to 6 K. Coercivity, mobility of the walls, and their variations with temperature are investigated. Wall velocity is observed to increase by orders of magnitude due to cooling from room to helium temperature in the case of current stimulated motion. The velocity becomes as high as the Walker velocity limit, about 1000 m/s. The walls are found to expand and tilt under the current pulses, which leads to their transformation into the domains with transverse magnetization.