Show simple item record

dc.contributor.authorCOEY, JOHN MICHAEL DAVID
dc.date.accessioned2009-08-12T10:17:55Z
dc.date.available2009-08-12T10:17:55Z
dc.date.issued2008
dc.date.submitted2008en
dc.identifier.citationL. Berger, Y. Labaye, M. Tamine, J.M.D. Coey 'Ferromagnetic nanoparticles with strong surface anisotropy: Spin structures and magnetisation processes' in Physical Review B - Condensed Matter and Materials Physics, 77, (10), 2008, no. 104431en
dc.identifier.otherYen
dc.identifier.otherY
dc.identifier.urihttp://hdl.handle.net/2262/31671
dc.descriptionPUBLISHEDen
dc.description.abstractMonte Carlo simulations are used to investigate the effect of surface anisotropy on the spin configurations and hysteresis loops of ferromagnetic nanoparticles. Spherical particles of radius ?a are composed of N atoms located on a simple cubic lattice with interatomic spacing a. The particles have 2???13. A classical Heisenberg model is assumed, with surface and bulk anisotropy. When surface anisotropy is positive there are two types of ground states separated by a large energy barrier: a ?throttled? configuration with reduced magnetization for intermediate values of surface anisotropy and a ?hedgehog? configuration with zero magnetization in the strong surface anisotropy limit. Beyond a threshold, surface anisotropy of either sign induces ?111? easy axes for the net magnetization. Easy-axis hysteresis loops are then square, with a continuous approach to saturation, and the effective anisotropy is deduced either from the switching field or from the initial slope of the perpendicular magnetization curve. The hedgehog state shows a stepwise magnetization curve involving ? discrete configurations, and it passes to a throttled configuration before saturating. The hysteresis loop has the unusual feature that it involves a state in the first quadrant, which lies on the reversible initial magnetization curve; it is possible to recover the zero-field cooled state after saturation. A survey of the exchange and anisotropy parameters for a range of ferromagnetic materials indicates that the effects of surface anisotropy on the spin configuration should be most evident in nanoparticles of ferromagnetic actinide compounds such as US, and rare-earth metals and alloys with Curie points below room temperature; the effects in nanoparticles of 3d ferromagnets and their alloys are usually insignificant, with the possible exception of FePt.en
dc.description.sponsorshipThis work was supported by the France-Ireland scientific exchange scheme, and by Science Foundation Ireland.en
dc.format.extentart no: 104431en
dc.format.extent1343775 bytes
dc.format.mimetypeapplication/pdf
dc.language.isoenen
dc.publisherAmerican Physcial Societyen
dc.relation.ispartofseriesPhysical Review B - Condensed Matter and Materials Physicsen
dc.relation.ispartofseries77en
dc.relation.ispartofseries10en
dc.rightsYen
dc.subjectPhysicsen
dc.titleFerromagnetic nanoparticles with strong surface anisotropy: Spin structures and magnetisation processesen
dc.contributor.sponsorScience Foundation Ireland
dc.type.supercollectionscholarly_publicationsen
dc.type.supercollectionrefereed_publicationsen
dc.identifier.peoplefinderurlhttp://people.tcd.ie/jcoey
dc.identifier.rssurihttp://dx.doi.org/10.1103/PhysRevB.77.104431


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record