40 research outputs found
Dipolar spin-misalignment correlations in inhomogeneous magnets: comparison between neutron scattering and micromagnetic approaches
In inhomogeneous bulk ferromagnets, the dominating sources of spin disorder
are related to spatial variations of (i) the magnitude of the local saturation
magnetization and of (ii) the magnitude and/or direction of the magnetic
anisotropy field. For the particular example of a porous ferromagnet, where the
magnetization inhomogeneity is at maximum, we demonstrate, by means of
experimental neutron scattering data and micromagnetic simulations, the
anisotropic character of magnetization fluctuations induced by the dipolar
interaction
Nonlinear magnetic vortex dynamics in a circular nanodot excited by spin-polarized current
We investigate analytically and numerically nonlinear vortex spin torque oscillator dynamics in a circular magnetic nanodot induced by a spin-polarized current perpendicular to the dot plane. We use a generalized nonlinear Thiele equation including spin-torque term by Slonczewski for describing the nanosize vortex core transient and steady orbit motions and analyze nonlinear contributions to all forces in this equation. Blue shift of the nano-oscillator frequency increasing the current is explained by a combination of the exchange, magnetostatic, and Zeeman energy contributions to the frequency nonlinear coefficient. Applicability and limitations of the standard nonlinear nano-oscillator model are discussed.This work was supported in part by the Spanish MINECO grant FIS2010-20979-C02-01. KYG acknowledges support by IKERBASQUE (the Basque Foundation for Science)
Comment on "Origin of Surface Canting within Nanoparticles"
We comment on the Letter "Origin of surface canting within
nanoparticles" by K.L. Krycka et al. [Phys. Rev.
Lett. , 147203 (2014)]
Towards understanding of magnetization reversal in Nd-Fe-B nanocomposites: analysis by high-throughput micromagnetic simulations
We demonstrate how micromagnetic simulations can be employed in order to characterize and
analyze the magnetic microstructure of nanocomposites. For the example of nanocrystalline
Nd-Fe-B, which is a potential material for future permanent-magnet applications, we have
compared three different models for the micromagnetic analysis of this material class: (i) a
description of the nanocomposite microstructure in terms of Stoner-Wohlfarth particles with
and without the magnetodipolar interaction; (ii) a model based on the core-shell representation
of the nanograins; (iii) the latter model including a contribution of superparamagnetic clusters.
The relevant parameter spaces have been systematically scanned with the aim to establish
which micromagnetic approach can most adequately describe experimental data for this
material. According to our results, only the last, most sophisticated model is able to provide
an excellent agreement with the measured hysteresis loop. The presented methodology is
generally applicable to multiphase magnetic nanocomposites and it highligths the complex
interrelationship between the microstructure, magnetic interactions, and the macroscopic
magnetic properties