Domain formation and long-range spin disorder in Vitroperm

ĽA. Michels1,2, J. Weissmüller1,2, R.N. Viswanath1, J.G. Barker3 und R. Hilzinger4
1Institut für Nanotechnologie, Forschungszentrum Karlsruhe, Karlsruhe, Germany
2Technische Physik, Universität des Saarlandes, Saarbrücken, Germany
3NIST Center for Neutron Research, Gaithersburg (MD), USA
4Vacuumschmelze GmbH, Hanau, Germany

We present a study of the magnetic-field dependence of the small-angle neutron scattering of the nanocrystalline melt-spun alloy Vitroperm (Fe73Si16B7Nb3Cu1), which was treated so as to exhibit a macroscopic magnetic anisotropy. For the situation in which the anisotropy axis is oriented perpendicular to the applied magnetic field Ha and perpendicular to the incoming neutron beam, we observe, upon decreasing the applied field starting from the magnetically saturated state, a change in the magnetic scattering contrast. In particular, we observe a gradual variation from the well known ``sin2J-law'', which is characteristic for the magnetic small-angle neutron scattering of saturated particles in a non-magnetic matrix, to a dominating ``cos2J-pattern'', which is ascribed to the onset of the formation of domains normal to Ha. The field dependence of the ratio of the scattering intensities parallel and perpendicular to Ha suggests (at the remanent state) the existence of magnetic correlations on a length scale of 100  nm and above.