MAGNETIC DOMAIN-WALL KINKING AND THE ALEONARD-BRISSONNEAU-NEEL EXPERIMENT

Neel's theory of the Aleonard-Brissonneau experiments to determine domain wall specific surface energy gamma 0 by observing the catastrophic torsional distortion of 180 degrees domain walls that span a monocrystalline platelet carrying a current density I is reviewed. It is shown that when I>0.924 gamma 0/JL2 (J is the saturation polarisation of the platelet of thickness 2L) Neel's domain wall profiles are only metastable against kink distortions of the Graham-Neurath type. Kinked profiles with lower energy have been calculated from the same equations and boundary conditions and these provide an alternative interpretation of the catastrophic transition observed. As it is not decisively clear which interpretation is correct, a degree of ambiguity would seem to exist concerning wall energies gamma 0 deduced from the published observations.