References of "Kohlbrecher, J"
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See detailMagnetic microstructure of a textured Nd-Fe-B sintered magnet characterized by small-angle neutron scattering
Périgo, E.A.; Mettus, Denis UL; Gilbert, E.P. et al

in Journal of Alloys & Compounds (2016), 661

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See detailPorosity-induced spin disorder in nanocrystalline inert-gas condensed iron
Michels, Andreas UL; Elmas, M.; Döbrich, Frank UL et al

in Europhysics Letters [=EPL] (2009), 85

We report magnetization and magnetic neutron scattering measurements on nanocrystalline Fe which was prepared by means of the inert-gas condensation technique. Depending on the compaction pressure applied ... [more ▼]

We report magnetization and magnetic neutron scattering measurements on nanocrystalline Fe which was prepared by means of the inert-gas condensation technique. Depending on the compaction pressure applied during the synthesis procedure (0.5–1.8 GPa), the resulting Fe samples contain porosity with volume fractions between about 20–35%. We provide evidence that the spin disorder which is associated with porosity has a strong influence on magnetic properties, and it gives rise to a characteristic clover-leaf–shaped angular anisotropy in the elastic-magnetic-scattering cross-section. [less ▲]

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See detailGrain-boundary-induced spin disorder in nanocrystalline gadolinium
Döbrich, Frank UL; Elmas, M.; Ferdinand, A. et al

in Journal of Physics : Condensed Matter (2009), 21(15), 1560031-1560035

Based on experimental magnetic-field-dependent neutron scattering data, we have calculated the autocorrelation function of the spin misalignment of nanocrystalline 160gadolinium. The analysis suggests the ... [more ▼]

Based on experimental magnetic-field-dependent neutron scattering data, we have calculated the autocorrelation function of the spin misalignment of nanocrystalline 160gadolinium. The analysis suggests the existence of two characteristic length scales in the spin system: the smaller one is about 5 nm and is attributed to the defect cores of the grain boundaries, whereas the larger length scale is of the order of the average crystallite size D = 21 nm and presumably describes the response of the magnetization to the magnetic anisotropy field of the individual crystallites. [less ▲]

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See detailSpin disorder at Gd grain boundaries
Döbrich, Frank UL; Elmas, M.; Ferdinand, A. et al

in Europhysics News (2009), 40/3

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See detailSpin structure of nanocrystalline gadolinium
Michels, Andreas UL; Döbrich, Frank UL; Elmas, M. et al

in Europhysics Letters [=EPL] (2008), 81

We report on magnetic-field–dependent small-angle neutron scattering (SANS) experiments on nanocrystalline inert-gas condensed bulk Gd, which was synthesized using the low-capturing isotope 160Gd. The ... [more ▼]

We report on magnetic-field–dependent small-angle neutron scattering (SANS) experiments on nanocrystalline inert-gas condensed bulk Gd, which was synthesized using the low-capturing isotope 160Gd. The angular dependency of the scattering cross-section is in very good agreement with recent theoretical predictions. Rather unexpected for this type of material, we observe a "clover-leaf–shaped" anisotropy in the SANS signal, the origin of which is attributed to the existence of longitudinal magnetization fluctuations associated with atomic site disorder and modified coupling inside the defect cores of grain boundaries. [less ▲]

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See detailCharacterisation of the polarised neutron beam at the small angle scattering instrument SANS-I with a polarised proton target
Aswal, V. K.; van den Brandt, B.; Hautle, P. et al

in Nuclear Instruments & Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment (2008), 586

A transmission neutron polariser (Fe/Si supermirror) has been successfully implemented in the small angle neutron scattering instrument SANS-I at the SINQ neutron source. The polariser is needed for ... [more ▼]

A transmission neutron polariser (Fe/Si supermirror) has been successfully implemented in the small angle neutron scattering instrument SANS-I at the SINQ neutron source. The polariser is needed for investigations of magnetic nanostructures as well as for spin contrast variation techniques relying on the spin-dependent neutron scattering length of polarised nuclei. The V-shaped polariser is installed in the first section of the collimator system of the SANS instrument and its performance is optimised for neutrons with a wavelength between 0.5 and 1.0 nm. For a precise polarisation analysis of a beam with selectable incident divergence, such as in SANS experiments, an opaque spin filter is ideal. We used a solid polarised proton target exploiting the strong spin-dependent neutron scattering cross-section of hydrogen and determined the neutron beam polarisation to a precision of 0.5% for different collimations in a broad wavelength band. [less ▲]

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See detailCreating local contrast in small-angle neutron scattering by dynamic nuclear polarization
van den Brandt, B.; Glattli, H.; Hautle, P. et al

in Journal of Applied Crystallography (2007), 40(s), 106-110

Low-resolution small-angle neutron scattering measurements can benefit from polarized protons to generate scattering contrast profiles. In a recently developed technique, time-resolved polarized SANS ... [more ▼]

Low-resolution small-angle neutron scattering measurements can benefit from polarized protons to generate scattering contrast profiles. In a recently developed technique, time-resolved polarized SANS tries to make use of spatial polarization gradients created around paramagnetic centres at the onset of dynamic nuclear polarization. The time constants which describe the build-up of polarization around the paramagnetic centre and the subsequent diffusion of polarization in the solvent were determined by analysing the temporal evolution of the nuclear polarization. The possible use and the limitations of this technique as a spectroscopic tool are discussed. [less ▲]

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See detailTemperature dependence of dipole-field scattering in Nanoperm
Michels, Andreas UL; Vecchini, C.; Moze, O. et al

in Journal of Magnetism & Magnetic Materials (2007), 316(2), 448-450

We present small-angle neutron scattering (SANS) data for the temperature variation of the recently observed dipole-field-induced spin-misalignment scattering in the soft magnetic nanocomposite Nanoperm ... [more ▼]

We present small-angle neutron scattering (SANS) data for the temperature variation of the recently observed dipole-field-induced spin-misalignment scattering in the soft magnetic nanocomposite Nanoperm (Fe89Zr7B3Cu1). The associated clover-leaf-shaped angular anisotropy of the SANS pattern, which is due to spin disorder arising from dipolar stray fields of the iron nanoparticles, persists up to several hundred Kelvin above the decoupling point of the intergranular amorphous matrix phase. This observation, in conjunction with the q-dependence of the scattering, suggests the existence of long-range magnetic correlations between the iron particles through the paramagnetic matrix, in agreement with previous investigations. The characteristic wavelength of the dipole-field-induced spin disorder appears to be temperature independent. [less ▲]

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See detailEffect of magnetic field annealing on the soft magnetic properties of nanocrystalline materials
Ito, N.; Michels, Andreas UL; Kohlbrecher, J. et al

in Journal of Magnetism & Magnetic Materials (2007), 316(2), 458-461

The effects of static- and rotating-magnetic-field annealing on the magnetic softness and the magnetization alignments in nanocrystalline Fe84Nb6B10 have been investigated by means of DC magnetometry and ... [more ▼]

The effects of static- and rotating-magnetic-field annealing on the magnetic softness and the magnetization alignments in nanocrystalline Fe84Nb6B10 have been investigated by means of DC magnetometry and small-angle neutron scattering (SANS). At the remanent state, the SANS pattern obtained from the static-field annealed sample exhibited an enhanced SANS signal in the direction normal to the uniaxial anisotropy (Ku) field direction, indicating a well-developed long-range magnetization alignment along the direction of Ku. Contrarily, the SANS pattern for the rotating-field annealed sample is virtually isotropic at zero field, reflecting the lack of anisotropic magnetization alignments. The soft magnetic properties of nanocrystalline Fe84Nb6B10 are improved dramatically by rotating-field annealing due to the suppression of Ku. [less ▲]

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See detailDipolar correlations in a nanocomposite: A neutron scattering study of Nanoperm Fe89Zr7B3Cu
Michels, Andreas UL; Vecchini, C.; Moze, O. et al

in Physical Review. B, Condensed Matter and Materials Physics (2006), 74(13), 1344071-13440713

We present results for the magnetic-field, temperature, and neutron-polarization dependence of the small-angle neutron scattering intensity in the soft magnetic iron-based nanocomposite Nanoperm ... [more ▼]

We present results for the magnetic-field, temperature, and neutron-polarization dependence of the small-angle neutron scattering intensity in the soft magnetic iron-based nanocomposite Nanoperm (Fe89Zr7B3Cu). An unusual “clover-leaf-shaped” intensity distribution on the detector is attributed to the dipolar stray fields around the nanosized iron particles, which are embedded in an amorphous magnetic matrix of lesser saturation magnetization. The dipole field induces spin disorder, correlating the spin misalignment of neighboring particles and matrix over several particle spacings. The clover-leaf-shaped anisotropy is observed over a wide range of applied magnetic field and momentum transfer. It persists up to several hundred degrees Kelvin above the Curie temperature of the matrix phase, indicating that some degree of magnetic coupling persists even when the matrix is paramagnetic. [less ▲]

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See detailTime-resolved nuclear spin-dependent small-angle neutron scattering from polarised proton domains in deuterated solutions
van den Brandt, B.; Glättli, H.; Grillo, I. et al

in European Physical Journal B -- Condensed Matter (2006), 49(2), 157-165

We have investigated the process of dynamic proton polarisation by means of time-resolved polarised small-angle neutron scattering (SANS) on frozen solutions of EHBA-CrV molecules in glycerol-water ... [more ▼]

We have investigated the process of dynamic proton polarisation by means of time-resolved polarised small-angle neutron scattering (SANS) on frozen solutions of EHBA-CrV molecules in glycerol-water mixtures as a function of the concentration of EHBA-CrV and for different degrees of deuteration of the solvent. In the EHBA-CrV complex, the spins of the 20 protons which surround the paramagnetic CrV can be oriented using the method of dynamic nuclear polarisation (DNP), thereby offering the possibility to create locally a nuclear spin-dependent contrast for SANS. The time constants which describe the build-up of polarisation around the paramagnetic centre and the subsequent diffusion of polarisation in the solvent were determined by analysing the temporal evolution of the nuclear polarisation, which in turn was obtained by fitting a core-shell model to the time-dependent SANS curves. The results on the spin dynamics obtained using the scattering function of a core-shell could be independently confirmed by evaluating the integrated SANS intensity. A thermodynamic one-centre model is presented which is able to reproduce the observed dependence of the proton polarisation times on the proton concentration of the solvent. [less ▲]

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See detailHigh-accuracy measurement of the spin-dependent neutron scattering length of the deuteron
van den Brandt, B.; Hautle, P.; Kohlbrecher, J. et al

in Proceedings of the 16th International Spin Physics Symposium and Workshop on Polarized Electron Sources and Polarimeters (2005)

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See detailAn experimental approach to the dynamics of nuclear polarisation
van den Brandt, B.; Glättli, H.; Grillo, I. et al

in Nuclear Instruments & Methods in Physics Research Section A (2004), 526

In the past 3 years a series of experiments have shed new light on the mechanism of dynamic nuclear polarisation (DNP). Time-resolved polarised small-angle neutron scattering and nuclear magnetic ... [more ▼]

In the past 3 years a series of experiments have shed new light on the mechanism of dynamic nuclear polarisation (DNP). Time-resolved polarised small-angle neutron scattering and nuclear magnetic resonance have been used simultaneously to study the nuclear polarisation build-up around paramagnetic centres during DNP. This approach, which aims at visualising the nuclear polarisation process on a microscopic scale, shall be exemplified and the experimental techniques used described in some detail. [less ▲]

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