skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: A new scaling approach for the mesoscale simulation of magnetic domain structures using Monte Carlo simulations

Authors:
; ;
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1396877
Grant/Contract Number:
AC05-00OR22725
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Journal of Magnetism and Magnetic Materials
Additional Journal Information:
Journal Volume: 432; Journal Issue: C; Related Information: CHORUS Timestamp: 2017-10-04 15:57:05; Journal ID: ISSN 0304-8853
Publisher:
Elsevier
Country of Publication:
Netherlands
Language:
English

Citation Formats

Radhakrishnan, B., Eisenbach, M., and Burress, T. A.. A new scaling approach for the mesoscale simulation of magnetic domain structures using Monte Carlo simulations. Netherlands: N. p., 2017. Web. doi:10.1016/j.jmmm.2017.01.064.
Radhakrishnan, B., Eisenbach, M., & Burress, T. A.. A new scaling approach for the mesoscale simulation of magnetic domain structures using Monte Carlo simulations. Netherlands. doi:10.1016/j.jmmm.2017.01.064.
Radhakrishnan, B., Eisenbach, M., and Burress, T. A.. Thu . "A new scaling approach for the mesoscale simulation of magnetic domain structures using Monte Carlo simulations". Netherlands. doi:10.1016/j.jmmm.2017.01.064.
@article{osti_1396877,
title = {A new scaling approach for the mesoscale simulation of magnetic domain structures using Monte Carlo simulations},
author = {Radhakrishnan, B. and Eisenbach, M. and Burress, T. A.},
abstractNote = {},
doi = {10.1016/j.jmmm.2017.01.064},
journal = {Journal of Magnetism and Magnetic Materials},
number = C,
volume = 432,
place = {Netherlands},
year = {Thu Jun 01 00:00:00 EDT 2017},
month = {Thu Jun 01 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.jmmm.2017.01.064

Citation Metrics:
Cited by: 1work
Citation information provided by
Web of Science

Save / Share:
  • A new scaling approach has been proposed for the spin exchange and the dipole–dipole interaction energy as a function of the system size. The computed scaling laws are used in atomistic Monte Carlo simulations of magnetic moment evolution to predict the transition from single domain to a vortex structure as the system size increases. The width of a 180° – domain wall extracted from the simulated structures is in close agreement with experimentally values for an F–Si alloy. In conclusion, the transition size from a single domain to a vortex structure is also in close agreement with theoretically predicted andmore » experimentally measured values for Fe.« less
  • A detailed description is provided of a new worm algorithm, enabling the accurate computation of thermodynamic properties of quantum many-body systems in continuous space, at finite temperature. The algorithm is formulated within the general path integral Monte Carlo (PIMC) scheme, but also allows one to perform quantum simulations in the grand canonical ensemble, as well as to compute off-diagonal imaginary-time correlation functions, such as the Matsubara Green function, simultaneously with diagonal observables. Another important innovation consists of the expansion of the attractive part of the pairwise potential energy into elementary (diagrammatic) contributions, which are then statistically sampled. This affords amore » complete microscopic account of the long-range part of the potential energy, while keeping the computational complexity of all updates independent of the size of the simulated system. The computational scheme allows for efficient calculations of the superfluid fraction and off-diagonal correlations in space-time, for system sizes which are orders of magnitude larger than those accessible to conventional PIMC. We present illustrative results for the superfluid transition in bulk liquid {sup 4}He in two and three dimensions, as well as the calculation of the chemical potential of hcp {sup 4}He.« less
  • Existing approaches for prediction of the tensor permeability of polycrystalline ferrites may not provide reasonable estimates of demagnetized permeability below the spin resonance (i.e., low-field loss region) or in cases of partial magnetization. We propose an approach which solves the coupled Landau-Lifshitz-Gilbert equation for the dynamic magnetic fields including the minimization of free energy to determine the equilibrium magnetization direction. Unlike previous models, we employ a Monte-Carlo approach to easily calculate the (ensemble) averages of permeability over various domain/grain structures and magnetic anisotropy conditions. Material differences, such as those resulting from different preparation methods, are expressed by using probability densitymore » functions (p.d.f.) for anisotropy angle (easy axis angle), grain demagnetization factor (ng), and domain demagnetization factor (nd). Effects on the permeability tensor of grain and domain demagnetization factors and anisotropy field relative to saturation magnetization are discussed for the partially magnetized states for polycrystalline ferrites. It is found that the grain structure (i.e., grain demagnetization distribution) has a smaller effect on the frequency dependent permeability than does the same distribution of domains (i.e., domain demagnetization distribution).« less
  • Recently, a pump beam size dependence of thermal conductivity was observed in Si at cryogenic temperatures using time-domain thermal reflectance (TDTR). These observations were attributed to quasiballistic phonon transport, but the interpretation of the measurements has been semi-empirical. Here, we present a numerical study of the heat conduction that occurs in the full 3D geometry of a TDTR experiment, including an interface, using the Boltzmann transport equation. We identify the radial suppression function that describes the suppression in heat flux, compared to Fourier's law, that occurs due to quasiballistic transport and demonstrate good agreement with experimental data. We also discussmore » unresolved discrepancies that are important topics for future study.« less
  • A novel way to attain three dimensional fluence rate maps from Monte-Carlo simulations of photon propagation is presented in this work. The propagation of light in a turbid medium is described by the radiative transfer equation and formulated in terms of radiance. For many applications, particularly in biomedical optics, the fluence rate is a more useful quantity and directly derived from the radiance by integrating over all directions. Contrary to the usual way which calculates the fluence rate from absorbed photon power, the fluence rate in this work is directly calculated from the photon packet trajectory. The voxel based algorithmmore » works in arbitrary geometries and material distributions. It is shown that the new algorithm is more efficient and also works in materials with a low or even zero absorption coefficient. The capabilities of the new algorithm are demonstrated on a curved layered structure, where a non-scattering, non-absorbing layer is sandwiched between two highly scattering layers.« less