•A. Michels^1,2, J. Weissmüller^1,2, R.N. Viswanath¹, J.G. Barker³ und R. Hilzinger^4
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 H_a 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 ``sin<sup>2</sup>J-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 H_a. The field dependence of the ratio of the scattering intensities parallel and perpendicular to H_a suggests (at the remanent state) the existence of magnetic correlations on a length scale of 100  nm and above.