Günther, A.; Bick, J.-P.; Szary, P.; Honecker, D.; Dewhurst, C.D.; Keiderling, U.; Feoktystov, A.V.; Tschoepe, A.; Birringer, R.; Michels, A.: Magnetic field dependent small-angle neutron scattering on a Co nanorod array: evidence for intraparticle spin misalignment. Journal of Applied Crystallography 47 (2014), p. 992-998
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The structural and magnetic properties of a cobalt nanorod array have been studied by means of magnetic field dependent small-angle neutron scattering (SANS). Measurement of the unpolarized SANS cross section d/d of the saturated sample in the two scattering geometries where the applied magnetic field H is either perpendicular or parallel to the wavevector ki of the incoming neutron beam allows one to separate nuclear from magnetic SANS, without employing the usual sector-averaging procedure. The analysis of the SANS data in the saturated state provides structural parameters (rod radius and centre-tocentre distance) that are in good agreement with results from electron microscopy. Between saturation and the coercive field, a strong field dependence of d/d is observed (in both geometries), which cannot be explained using the conventional expression of the magnetic SANS cross section of magnetic nanoparticles in a homogeneous nonmagnetic matrix. The origin of the strong field dependence of d/d is believed to be related to intradomain spin misalignment, due to magnetocrystalline and magnetoelastic anisotropies and magnetostatic stray fields.