Low Temperature Motion of Néel and Bloch Walls

The motion of Néel and Bloch walls in a quasistatic magnetic field was investigated by Lorentz microscopy in the range 4 to 300°K. Below a critical temperature (28 °K for polycrystalline Permalloy and 40°K for poly‐ and monocrystalline iron and cobalt films) the usual Barkhausen jumps of the wall motion with jump size 1 to 50 μm were abruptly quenched. The wall then moved by tiny jumps (size ≈ 0.1 or < 0.03 μm) and in a constant field. These effects – associated with the motion of Néel, Bloch, cross‐tie walls and circle Bloch lines along the walls of locked domains – were ascribed to the suppression of the diffusion and orientation after‐effect of crystal defects.