Abstract
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 dΣ/dΩ 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-to-centre distance) that are in good agreement with results from electron microscopy. Between saturation and the coercive field, a strong field dependence of dΣ/dΩ 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 dΣ/dΩ is believed to be related to intradomain spin misalignment, due to magnetocrystalline and magnetoelastic anisotropies and magnetostatic stray fields.
Highlights
As a consequence of their interesting magnetic properties, magnetic transition-metal nanorod arrays are attracting much scientific attention (Fert & Piraux, 1999; Sellmyer et al, 2001; Kou et al, 2011; Greaves et al, 2012)
The experimental differential Small-angle neutron scattering (SANS) cross sections dÆ=d of the Co nanorod array for the two scattering geometries are shown in Fig. 5 for selected applied magnetic fields between
With decreasing magnetic field, scattering due to transverse spin components emerges at smaller q and a maximum intensity can be observed at the coercive field 0Hc 1⁄4 À0:05 T (Fig. 5a, right)
Summary
As a consequence of their interesting magnetic properties, magnetic transition-metal nanorod arrays are attracting much scientific attention (Fert & Piraux, 1999; Sellmyer et al, 2001; Kou et al, 2011; Greaves et al, 2012). It is their pronounced magnetic shape anisotropy which largely determines the magnetization process in these systems and which renders them potential candidates for perpendicular magnetic storage media (Ross et al, 1999; Greaves et al, 2012). Cryst. (2014). 47, 992–998 research papers magnetic SANS cross section, which assumes uniformly magnetized particles
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