Observation of <i>s</i>-<i>d</i> exchange force between domain walls and electric current in very thin Permalloy films

Abstract

Large dc current pulses, ≂2 μs long, are sent through 30–40-nm-thick Ni87Fe13 films containing Néel walls. Wall displacements are seen for current densities ≥1.2×107 A/cm2. Displacements reverse when current sense is reversed. Walls always move in direction of charge carriers in this electronlike material. Our results agree with a theory of s-d exchange interaction between walls and 4s conduction electrons. Hydromagnetic ‘‘domain-drag’’ forces are too small in such very thin films to explain our data.