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See detailField-Induced Spin Helix Chirality in Nanocrystalline Ho
Szary, Philipp UL; Bick, Jens-Peter UL; Kaiser, Daniel UL et al

Poster (2014, November)

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See detailNeutronenstreuuntersuchungen zur magnetischen Mikrostruktur Nd-Fe-B-basierter Nanokomposite
Bick, Jens-Peter UL

Doctoral thesis (2014)

Exchange-coupled magnetic nanocomposites are considered to be promising candidates for future permanent magnet applications. These nanocomposites consist of a hard magnetic phase (based on rare-earth ... [more ▼]

Exchange-coupled magnetic nanocomposites are considered to be promising candidates for future permanent magnet applications. These nanocomposites consist of a hard magnetic phase (based on rare-earth metal alloys), which provides high magnetic anisotropy and which is exchange coupled to a soft magnetic rare earth free phase, which provides a high saturation magnetization and Curie-temperatur. For suitable microstructures one could achieve on the one hand side dramatically increased energy products, in comparison to state-of-the-art Dy-Nd-Fe-B magnets. On the other hand side – due to the reduced amount of rare earth metals – expenses could be saved significantly. The understanding of the coercivity mechanisms in these materials is crucial for the development of nanocomposite permanent magnets. In the present work, the magnetization reversal of a two-phase Nd2Fe14B/Fe3B nanocomposite has been studied by means of magnetic small angle neutron scattering (SANS). This technique exclusively provides access to information of the magnetic microstructure in the bulk of the material and on the relevant length scales of 1 − 100 nm. Direct Fourier-transformation allowed the calculation of the correlation function of the spin misalignment C(r). From this data, the correlation length lc has been obtained. The parameter lc is a measure for the spatial extent of magnetization inhomogeneities. The field dependence of lc indicates a magnetization reversal process, which is widely governed by homogeneous rotation of the magnetization within the hard magnetic Nd2Fe14B particles. In addition, in terms of a micromagnetic approach, the exchange stiffness constant A was determined experimentally. [less ▲]

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See detailField-induced spin helix chirality in nanocrystalline Ho
Szary, Philipp UL; Bick, Jens-Peter UL; Malyeyev, Artem et al

Poster (2014, April)

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See detailExchange-stiffness constant of a Nd-Fe-B based nanocomposite determined by magnetic neutron scattering
Bick, Jens-Peter UL; Suzuki, Kiyonori; Gilbert, Elliot et al

in Applied Physics Letters (2013), 103

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See detailAutocorrelation function of the spin misalignment in magnetic small-angle neutron scattering: application to nanocrystalline metals
Michels, Andreas UL; Bick, Jens-Peter UL

in Journal of Applied Crystallography (2013), 46

Real-space magnetic small-angle neutron scattering data from nanocrystalline cobalt and nickel have been analysed in terms of a recently developed micromagnetic theory for the autocorrelation function of ... [more ▼]

Real-space magnetic small-angle neutron scattering data from nanocrystalline cobalt and nickel have been analysed in terms of a recently developed micromagnetic theory for the autocorrelation function of the spin misalignment [Michels (2010). Phys. Rev. B, 82, 024433]. The approach provides information on the exchange-stiffness constant and on the mean magnetic ‘anisotropy-field’ radius. [less ▲]

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See detailMagnetization reversal in Nd-Fe-B based nanocomposites as seen by magnetic small-angle neutron scattering
Bick, Jens-Peter UL; Honecker, Dirk UL; Döbrich, Frank UL et al

in Applied Physics Letters (2013), 102(2), 0224151-0224155

We have studied the magnetization-reversal process of a Nd2Fe14B/Fe3B nanocomposite using small-angle neutron scattering. Based on the computation of the autocorrelation function of the spin misalignment ... [more ▼]

We have studied the magnetization-reversal process of a Nd2Fe14B/Fe3B nanocomposite using small-angle neutron scattering. Based on the computation of the autocorrelation function of the spin misalignment, we have estimated the characteristic size lC of spin inhomogeneities around the Nd2Fe14B nanoparticles. The quantity lC approaches a constant value of about 12.5 nm ( ∼ average Nd2Fe14B particle radius) at 14 T and takes on a maximum value of about 18.5 nm at the coercive field of −0.55 T. The field dependence of lC can be described by a model that takes into account the convolution relationship between the nuclear and the magnetic microstructure. [less ▲]

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See detailInfluence of crystallite size and temperature on the antiferromagnetic helices of terbium and holmium metal
Michels, Andreas UL; Bick, Jens-Peter UL; Birringer, R. et al

in Physical Review. B, Condensed Matter and Materials Physics (2011), 83

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