Characteristic magnetic length-scales in Vitroperm - Combining Kerr microscopy and small-angle neutron scattering

Grob, A.; Saranu, S.; Herr, U.; Michels, Andreas; Viswanath, R. N.; Weißmüller, J.

doi:10.1002/pssa.200405533

Cited by 18 publications

(22 citation statements)

References 18 publications

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“…[5]) suggest that the internal magnetic field necessary to saturate these materials is indeed several orders of magnitude smaller than the above estimate for the demagnetizing field, it can be expected that in the SANS experiment the transition between a single domain and a multi-domain structure occurs in an applied-field range of roughly 20-30 mT. In a recent SANS investigation, which also used a sample of non-ellipsoidal shape [5], the estimated value for the volume-averaged magnetometric demagnetizing field was in excellent agreement with the observed onset of domain formation and was independently confirmed by Kerr microscopy [9]. Fig.…”

Section: Resultssupporting

confidence: 66%

Small angle neutron scattering investigations of spin disorder in nanocomposite soft magnets

Vecchini

Može

Suzuki

et al. 2006

Journal of Alloys and Compounds

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Section: Resultssupporting

confidence: 66%

Small angle neutron scattering investigations of spin disorder in nanocomposite soft magnets

Vecchini

Može

Suzuki

et al. 2006

Journal of Alloys and Compounds

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“…The terms in Eqs. (15) and (16) which contain the Fourier coefficient M z (q) ∝ ∆M model the influence of the two-phase magnetic microstructure on the magnetic SANS and are not contained in the corresponding expressions for the single-phase case (compare Eqs. (2.15) in Ref.…”

Section: Micromagnetic Modelmentioning

confidence: 99%

“…43,44 In the derivation of Eqs. (15) and (16) terms of higher than linear order in M x or M y have been neglected, in-cluding terms such as 27 Besides this small-misalignment approximation, we have introduced two further approximations: (i) The exchange interaction is assumed to be homogeneous, i.e., jumps in A between the two magnetic phases have not been taken into account. Such an approximation is permissable as long as exchange fluctuations are not too large, in particular, for soft magnetic materials.…”

Section: Micromagnetic Modelmentioning

confidence: 99%

“…[39][40][41] For the following discussion of magnetic SANS it is of interest to consider special projections of Eqs. (15) and (16) into the plane of the 2D detector. The two scattering geometries which are of particular relevance to experiment have the external magnetic field H 0 either perpendicular or parallel to the wave vector k 0 of the incoming neutron beam.…”

Section: Micromagnetic Modelmentioning

confidence: 99%

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Theory of magnetic small-angle neutron scattering of two-phase ferromagnets

Honecker

Michels

2013

Phys. Rev. B

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Based on micromagnetic theory we have derived analytical expressions for the magnetic smallangle neutron scattering (SANS) cross section of a two-phase particle-matrix-type ferromagnet. The approach-valid close to magnetic saturation-provides access to several features of the spin structure such as perturbing magnetic anisotropy and magnetostatic fields. Depending on the applied magnetic field and on the magnitude Hp of the magnetic anisotropy field relative to the magnitude ∆M of the jump in the longitudinal magnetization at the particle-matrix interface, we observe a variety of angular anisotropies in the magnetic SANS cross section. In particular, the model explains the "clover-leaf"-shaped angular anisotropy which was previously observed for several nanostructured magnetic materials, and it provides access to the magnetic interaction parameters such as the average exchange-stiffness constant. It is also shown that the ratio Hp/∆M decisively determines the asymptotic power-law exponent and the range of spin-misalignment correlations.

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“…When the average grain size D is less than the exchange length = ( / ) K l AK 1 (where A and K 1 denote the exchange constant and anisotropy energy constant, respectively), the spin system decorates an effective anisotropy which is averaged over many grains. Small angle neutron scattering (SANS) is a suitable technique to study the micromagnetic structure of these materials at the nanometer scale [2][3][4][5][6][7]. However, the interpretation of the scattering curves is not always straightforward due to effects such as sample inhomogeneities resulting from phase separation in the case of Vitroperm, or residual porosity.…”

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confidence: 99%

Micromagnetic structures of nanocrystalline ferromagnetic materials – comparison of simulation and experiment

Saranu

Grob

Weißmüller

et al. 2008

Physica Status Solidi (a)

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The micromagnetic structure of nanocrystalline ferromagnetic materials is characterized by local fluctuations induced by the randomly varying magnetocrystalline anisotropy of the individual grains. Micromagnetic simulations may improve the understanding of the relevant features and the interpretation of the experimental observations of the magnetic structure. In this study we investigate the magnetic structure of nanocrystalline FeSi and Co model systems with average grain sizes of 20 nm to 60 nm. Small angle neutron scattering (SANS) is a suitable technique to study the micromagnetic structures of nanocrystalline materials at the nanometer scale. The simulated SANS curves for the FeSi model systems are compared with the experimental SANS curves of Vitroperm samples. It is found that the scattering at high fields is dominated by the local anisotropy fluctuations which can be well reproduced by the simulations. The simulations of the nanocrystalline hcp Co show that the stray fields resulting from the local magnetic fluctuations should lead to an observable contrast in magnetic force microscopy (MFM) images. We show that the contrast observed in the real MFM images of thin nanocrystalline hcp Co films compares well with the simulated image contrast with respect to magnitude and length scale of the observed fluctuations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Characteristic magnetic length-scales in Vitroperm - Combining Kerr microscopy and small-angle neutron scattering

Cited by 18 publications

References 18 publications

Small angle neutron scattering investigations of spin disorder in nanocomposite soft magnets

Small angle neutron scattering investigations of spin disorder in nanocomposite soft magnets

Theory of magnetic small-angle neutron scattering of two-phase ferromagnets

Micromagnetic structures of nanocrystalline ferromagnetic materials – comparison of simulation and experiment

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