Magnetic Guinier law

in IUCrJ (2020), 7

Small-angle scattering of x-rays and neutrons is a routine method for the determination of nanoparticle sizes. The so-called Guinier law represents the low-q approximation for the small-angle scattering ... [more ▼]

Small-angle scattering of x-rays and neutrons is a routine method for the determination of nanoparticle sizes. The so-called Guinier law represents the low-q approximation for the small-angle scattering curve from an assembly of particles. The Guinier law has originally been derived for nonmagnetic particle-matrix-type systems, and it is successfully employed for the estimation of particle sizes in various scientific domains (e.g., soft matter physics, biology, colloidal chemistry, materials science). An important prerequisite for it to apply is the presence of a discontinuous interface separating particles and matrix. Here, we introduce the Guinier law for the case of magnetic small-angle neutron scattering (SANS) and experimentally demonstrate its applicability for the example of nanocrystalline cobalt. It is well- known that the magnetic microstructure of nanocrystalline ferromagnets is highly nonuniform on the nanometer length scale and characterized by a spectrum of continuously varying long-wavelength magnetization fluctuations, i.e., these systems do not manifest sharp interfaces in their magnetization profile. The magnetic Guinier radius depends on the applied magnetic field, on the magnetic interactions (exchange, magnetostatics), and on the magnetic anisotropy-field radius, which characterizes the size over which the magnetic anisotropy field is coherently aligned into the same direction. In contrast to the nonmagnetic conventional Guinier law, the magnetic version can be applied to fully dense random-anisotropy-type ferromagnets. [less ▲]

Effect of grain-boundary diffusion process on the geometry of the grain microstructure of Nd−Fe−B nanocrystalline magnets

in Physical Review Materials (2019), 3(084410),

Magnetic Guinier Law

Poster (2019, June)

We introduce the Guinier law for the case of magnetic SANS and provide an analysis of experimental data on a Nd-Fe-B-based nanocomposite and on a rare-earth-free MnBi permanent magnet. The robustness of ... [more ▼]

We introduce the Guinier law for the case of magnetic SANS and provide an analysis of experimental data on a Nd-Fe-B-based nanocomposite and on a rare-earth-free MnBi permanent magnet. The robustness of this novel approach is discussed and the quantities derived are analyzed in the framework of the existing research literature. [less ▲]

Magnetic small-angle neutron scattering

in Reviews of Modern Physics (2019), 91

Erratum: Third-order effect in magnetic small-angle neutron scattering by a spatially inhomogeneous medium [Phys. Rev. B 91, 054404 (2015)]

in Physical Review. B, Condensed Matter and Materials Physics (2019), 99

Magnetic neutron scattering on nanomagnets

Scientific Conference (2018, September 26)

Magnetic neutron scattering on bulk ferromagnets

Presentation (2018, July 12)

Magnetic neutron scattering studies on magnetic materials

Scientific Conference (2018, March 11)

Effect of annealing conditions on the microstructure and magnetic properties of sintered Nd-Fe-B magnets as seen by magnetic smallangle neutron scattering

in Materials Research Express (2018), 5

Magnetic SANS as a probe to disclose internal interfaces and the spin structure of nanoparticles

Scientific Conference (2017, October 11)