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Magnetic moments of Fe clusters embedded in an Fe-Co alloy
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
2006 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 74, no 10, 104422- p.Article in journal (Refereed) Published
Abstract [en]

Motivated by the search for high moment materials, we present first-principles calculations of the magnetic moments for Fe clusters embedded in an Fe-Co alloy as well as in a pure Co matrix. Both spin and orbital contributions have been calculated with the use of a real-space linear muffin-tin orbital method within the atomic sphere approximation. The cluster sizes considered range from 1 to 51 atoms. We find an enhancement of the spin moments of the atoms close to the interface between the cluster and the embedding matrix. The spin moment enhancement is decreasing with increasing Fe content in the surrounding matrix. The slightly lower magnetic moments for the Fe clusters embedded in the Fe rich matrices can nevertheless result in a material with an enhanced saturation magnetization due to the higher moments in the matrix. We argue that the largest average magnetic moments for embedded Fe clusters are obtained for an Fe0.5Co0.5 alloy in the matrix surrounding the clusters.

Place, publisher, year, edition, pages
2006. Vol. 74, no 10, 104422- p.
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-94293DOI: 10.1103/PhysRevB.74.104422ISI: 000240872000066OAI: oai:DiVA.org:uu-94293DiVA: diva2:168094
Available from: 2006-04-12 Created: 2006-04-12 Last updated: 2012-03-14Bibliographically approved
In thesis
1. A Theoretical Study of Magnetism in Nanostructured Materials
Open this publication in new window or tab >>A Theoretical Study of Magnetism in Nanostructured Materials
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A first-principles linear scaling real-space method for investigating non-collinear magnetic behaviour of nanostructured materials has been developed. With this method, the magnetic structures of small supported transition metal clusters have been examined. The geometric constraints imposed on the clusters by the underlying surface is found to cause non-collinear behaviour for V, Cr, and Mn clusters on Cu(111). Fe clusters supported on Cu and Ni have been studied and both spin and orbital moments are found to be enhanced for the Fe atoms, which is attributed to the recuced symmetry present at the surface. Atoms in Co clusters have been found to order antiferromagnetically, and some times in a non-collinear fasion, when deposited on a W surface. Small clusters of fcc Fe embedded in Cu have been examined and a new type of ordering, not present in larger fcc Fe systems was found.

Several theoretical studies of Fe and Co based nanostructures consisting of multilayers or embedded clusters have been conducted, with the aim of predicting high moment materials for use in data storage applications. In agreement with previous experiments an enhancement of the magnetic moment is found compared to the magnetic moment of bcc Fe. The enhancement has been shown to be caused by increased spin moments for Fe atoms in close proximity with Co atoms, and this enhancement depends on the number of Co neighbours. As a result of these studies, a possible method of increasing the magnetic moment of cluster based materials has been proposed.

Fermi surface analysis have been performed both on bulk materials, in order to investigate mechanisms for stabilizing non-collinear magnetic states, and in layered structures where the effect of the Fermi surface on the interlayer exchange coupling has been investigated.

In addition to the development of a real-space electronic structure method for non-collinear magnetism, a density matrix purification method has been implemented in the framework of linear muffin-tin orbitals.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2006. x + 78 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 167
Keyword
Physics, magnetism, clusters, non-collinear, multilayers, first-principles theory, electronic structure, high-moment materials, exchange interactions, linear scaling methods, Fysik
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-6763 (URN)91-554-6527-7 (ISBN)
Public defence
2006-05-05, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2006-04-12 Created: 2006-04-12 Last updated: 2012-03-27Bibliographically approved

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Bergman, AndersEriksson, Olle

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