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

Title: Dynamic origin of stripe domains in cobalt bars.

Abstract

Based on dynamical calculations, we theoretically study the nucleation of stripe domains in single-crystal Co bars. Three different stripe domain structures at remanence are obtained in micromagnetic simulations depending on different field histories. We show that the nucleation of all three stripe domains are related to soft mode instabilities. When the field is along the long axis of the bar, the remanent stripe domain structure is shown to be generated by a standing-wave mode, that has the same spatial structure as the stripes at remanence and goes soft at a second-order phase transition where the stripe domains emerge. For the other two directions of the field, we find that the symmetry of soft modes is consistent with the change in symmetry of the ground state but in these cases the phase transition is first order.

Authors:
; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC); OUS
OSTI Identifier:
1000654
Report Number(s):
ANL/MCS/CP-118796
Journal ID: 0304-8853; TRN: US201101%%352
DOE Contract Number:
DE-AC02-06CH11357
Resource Type:
Conference
Resource Relation:
Journal Name: J. Magn. Magn. Mater.; Journal Volume: 2; Journal Issue: 310 ; Mar. 2007; Conference: 17th International Conference on Magnetism (ICM); Aug. 20, 2006 - Aug. 25, 2006; Kyoto, Japan
Country of Publication:
United States
Language:
ENGLISH
Subject:
36 MATERIALS SCIENCE; COBALT; DOMAIN STRUCTURE; GROUND STATES; MAGNETISM; NUCLEATION; ORIGIN; SIMULATION; SPIN; SYMMETRY; PHASE TRANSFORMATIONS

Citation Formats

Yan, M., Leaf, G., Kaper, H., Novosad, V., Vavassori, P., Camley, R. E., Grimsditch, M., Univ. of Ferrara, and Univ. of Colorado. Dynamic origin of stripe domains in cobalt bars.. United States: N. p., 2007. Web. doi:10.1016/j.jmmm.2006.10.1127.
Yan, M., Leaf, G., Kaper, H., Novosad, V., Vavassori, P., Camley, R. E., Grimsditch, M., Univ. of Ferrara, & Univ. of Colorado. Dynamic origin of stripe domains in cobalt bars.. United States. doi:10.1016/j.jmmm.2006.10.1127.
Yan, M., Leaf, G., Kaper, H., Novosad, V., Vavassori, P., Camley, R. E., Grimsditch, M., Univ. of Ferrara, and Univ. of Colorado. Thu . "Dynamic origin of stripe domains in cobalt bars.". United States. doi:10.1016/j.jmmm.2006.10.1127.
@article{osti_1000654,
title = {Dynamic origin of stripe domains in cobalt bars.},
author = {Yan, M. and Leaf, G. and Kaper, H. and Novosad, V. and Vavassori, P. and Camley, R. E. and Grimsditch, M. and Univ. of Ferrara and Univ. of Colorado},
abstractNote = {Based on dynamical calculations, we theoretically study the nucleation of stripe domains in single-crystal Co bars. Three different stripe domain structures at remanence are obtained in micromagnetic simulations depending on different field histories. We show that the nucleation of all three stripe domains are related to soft mode instabilities. When the field is along the long axis of the bar, the remanent stripe domain structure is shown to be generated by a standing-wave mode, that has the same spatial structure as the stripes at remanence and goes soft at a second-order phase transition where the stripe domains emerge. For the other two directions of the field, we find that the symmetry of soft modes is consistent with the change in symmetry of the ground state but in these cases the phase transition is first order.},
doi = {10.1016/j.jmmm.2006.10.1127},
journal = {J. Magn. Magn. Mater.},
number = 310 ; Mar. 2007,
volume = 2,
place = {United States},
year = {Thu Mar 01 00:00:00 EST 2007},
month = {Thu Mar 01 00:00:00 EST 2007}
}

Conference:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this conference proceeding.

Save / Share:
  • No abstract prepared.
  • No abstract prepared.
  • Two- and three-dimensional time dependent explicit finite difference methods are used to analyze the stress field around cracks subjected to dynamic tensile loads. Several different notch radii of a notched central crack in a rectangular bar are studied. Both plane strain and plane stress loadings are included. The stress field around a through-the-thickness crack in a section of a cylindrical pipe loaded by a sudden application of pressure is calculated. The plastic strain field around an edge crack in a bar is calculated in plane strain and plane stress geometry. It is pointed out that complex models of material behaviormore » can be easily incorporated into the calculation, but it is the simple elastic material with a sharp crack that places the greatest demands on the calculational procedures. Extrapolation methods are used to determine dynamic stress conditions at the tip of sharp cracks in elastic materials. For rounded cracks, or a crack blunted by plastic flow, the dynamic stress state at a crack tip can be calculated directly.« less
  • The microstructure of two commercial 2:17 precipitation hardened rare-earth magnets has been examined and compared with the magnetic properties. Transmission electron microscope studies on Sm(Co,Fe,Cu,Hf)/sub 7/ /sub 25/, Hicorex 99C show a fine cellular microstructure with 2:17 rhombohedral cells surrounded by coherent 1:5 hexagonal cell boundaries. In Sm(Co,Fe,Cu,Zr)/sub 7/ /sub 22/, TDK REC-26 the cells are much coarser and 1:3 phase thin lamellae are superimposed on the cellular structure. X-ray energy dispersive analysis shows a higher Cu content in the cell boundaries. Lorentz electron microscopy shows wavy domain walls in both cases indicating that the domain walls are pinned atmore » the cell boundaries. The higher Cu content of the cell boundaries dilutes the magnetic properties of the SmCo/sub 5/, phase and produces a large domain wall energy gradient across the cell boundary leading to the observed high coercivities.« less
  • Fracture permeability is of primary importance to producibility of coalbed methane. To evaluate controls on fracture (cleat) patterns in coal beds in the Upper Cretaceous Fruitland Formation in the San Juan basin, the authors studied fractures in the coal and adjacent sandstones in 11 cores and 90 outcrop stations along the basin margin and mapped fractures in selected areas. Cleats are perpendicular to bedding, planar, usually uniform in strike within an outcrop or core, and arranged in closely spaced subparallel sets. Face cleats are the first formed (and generally most prominent) fractures; butt cleats formed later, and most cases strikemore » perpendicular to the face cleat. Timing of cleat development is constrained by the age of cleats relative to dated folds and the burial history of the Fruitland Formation. Where beds ar reoriented by folds, cleats remain orthogonal to bedding, indicating that they formed prior to fold development during the early Tertiary. Cleat crosscuts bedding-parallel coal compaction fabrics, indicating that cleat formed later. Cleat development was contemporaneous with orogenesis in the Cordilleran belt, in progress during late Campanian time. Patterns reflect lateral stresses associated with northeast- and southeast-directed Cordilleran orogenic movements. Domains may represent separate deformation events or contemporaneous paleostress provinces. Contrasts in cleat development in individual domains can affect hydraulic fracture treatment or cavity completion. The prevalence of strongly developed face and butt cleat in the domain-boundary region and resulting increased coal friability may increase the success of cavity completions in this areas.« less