MAGNETIC SMALL-ANGLE NEUTRON SCATTERING ON BULK METALLIC GLASSES

Scientific Conference (2017, July 03)

Magnetic small-angle neutron scattering on bulk metallic glasses

Scientific Conference (2016, March 08)

Bulk metallic glasses (BMG) are amorphous solids which are very well known for their excellent mechanical properties. In this contribution, we focus on their magnetic behavior and we discuss the influence ... [more ▼]

Bulk metallic glasses (BMG) are amorphous solids which are very well known for their excellent mechanical properties. In this contribution, we focus on their magnetic behavior and we discuss the influence of mechanical deformation on the magnetic microstructure as seen by magnetic-field-dependent small-angle neutron scattering (SANS). This technique allows one to investigate the spin distribution in the bulk of the material and on the nanometer length scale. We present and compare the results of unpolarized SANS on various BMG samples (as-cast, aged, deformed) and we analyze the SANS cross section in real space by computing the correlation function. [less ▲]

Small-angle neutron scattering of nanocrystalline gadolinium and holmium with random paramagnetic susceptibility

in Journal of Physics : Condensed Matter (2015), 27

Magnetization reversal in Nd-Fe-B based nanocomposites as seen by magnetic small-angle neutron scattering

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 ▲]

Synthesis and characterization of uniaxial ferrogels with Ni nanorods as magnetic phase

in Journal of Magnetism and Magnetic Materials (2011), 323

In the present study, the rotation of magnetic nanorods in a soft hydrogel matrix induced by a homogeneous magnetic field is investigated. Magnetic nanorods of ≈151.2 nm length and ≈17.7 nm diameter are ... [more ▼]

In the present study, the rotation of magnetic nanorods in a soft hydrogel matrix induced by a homogeneous magnetic field is investigated. Magnetic nanorods of ≈151.2 nm length and ≈17.7 nm diameter are synthesized via current-pulsed electrodeposition of nickel into porous aluminum oxide-templates. The nanorods are processed towards a stable colloidal dispersion by dissolution of the alumina template in aqueous NaOH to which PVP (polyvinyl-pyrrolidone) is added as surfactant. These suspensions are used to prepare gelatine-based ferrogels of different shear modulus with either isotropic or uniaxial orientation-distribution of the nanorods. While magnetization measurements of rigid ferrogels mainly reflect the magnetic properties of the nickel nanorods, the magnetization behavior of soft ferrogels is significantly influenced by a field-induced rotation of the nickel nanorods in the low compliant matrix. A particular analysis of magnetization measurements on uniaxial ferrogels enables to quantify the rotation angle of the nanorods with respect to their initial orientation under the influence of a transversal homogeneous magnetic field. The analysis of the field-dependent rotation also allows to estimate the local shear modulus of the matrix which is demonstrated by an investigation of room temperature ageing process of the ferrogel. [less ▲]

Magnetic-field-dependent optical transmission of nickel nanorod colloidal dispersions

in Journal of Applied Physics (2009), 106

Aqueous dispersions of nickel nanorods, ~13 nm in diameter and 40–160 nm in length, were synthesized using ac electrodeposition into porous alumina templates. The nanorods in suspension can be aligned by ... [more ▼]

Aqueous dispersions of nickel nanorods, ~13 nm in diameter and 40–160 nm in length, were synthesized using ac electrodeposition into porous alumina templates. The nanorods in suspension can be aligned by modest magnetic fields, which leads to a change in the optical transmittance of the dispersion. Optical transmission measurements with polarized and unpolarized light as a function of magnetic field were performed on suspensions of different particle concentration and varying aspect ratio of the nanoparticles. The experimental results were compared with a theoretical model in which the optical absorption of the nanorods is calculated from the polarizability of prolate ellipsoids in the quasistatic approximation. The magnetic field dependence is introduced in terms of the static orientational distribution function of magnetic moments in an external field. In addition, the relaxation dynamics of the optical transmission was studied, which allowed us to determine the rotational diffusion coefficient of the nanorods in suspension. [less ▲]