Measurement of a magnetic-field dependent correlation length in nanocrystalline Ni using small-angle neutron scattering

We have analyzed magnetic-field dependent small-angle neutron scattering data on nanocrystalline electrodeposited Ni by means of the correlation function of the spin misalignment. The approach yields a correlation length lC of the spin misalignment that is a measure for the characteristic dimension of regions in which the magnetic moments are misaligned coherently into a common direction. We find that lC varies strongly with the applied magnetic field Hi with values extending from about 50 nm (larger than the value for uniformly magnetized grains) at small Hi to about 10 nm (considerably smaller than the grain size) at large applied fields.