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XANES studies of Mn K and L-3,L-2 edges in the (Ga,Mn) As layers modified by high temperature annealing
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2008 (English)In: Acta Physica Polonica. A, ISSN 0587-4246, E-ISSN 1898-794X, Vol. 114, no 2, 357-366 p.Article in journal (Refereed) Published
Abstract [en]

Ga1-xMnx As is commonly considered as a promising material for microelectronic applications utilizing the electron spin. One of the ways that allow increasing the Curie temperature above room temperature is to produce second phase inclusions. In this paper Gal-,Mn.As samples containing precipitations of ferromagnetic MnAs are under consideration. We focus on the atomic and electronic structure around the Mn atoms relating to the cluster formation. The changes in the electronic structure of the Mn, Ga and As atoms in the (Ga,Mn)As layers after high temperature annealing were determined by X-ray absorption near edge spectroscopy. The experimental spectra were compared with the predictions of ab initio full multiple scattering theory using the FEFF 8.4 code. The nominal concentration of the Mn atoms in the investigated samples was 6% and 8%. We do not observe changes in the electronic structure of Ca and As introduced by the presence of the Mn atoms. We find, in contrast, considerable changes in the electronic structure around the Mn atoms. Moreover, for the first time it was possible to indicate the preferred interstitial positions of the Mn atoms.

Place, publisher, year, edition, pages
2008. Vol. 114, no 2, 357-366 p.
National Category
Physical Sciences
URN: urn:nbn:se:uu:diva-149514ISI: 000258163200007OAI: oai:DiVA.org:uu-149514DiVA: diva2:405087

Conference Information: 7th National Meeting of the Synchrotron Radiation Users Poznan, POLAND, SEP 24-26, 2007

Available from: 2011-03-21 Created: 2011-03-20 Last updated: 2016-04-29
In thesis
1. X-ray Absorption Spectroscopy on Nano-Magnet Arrays and Thin Films: Magnetism and Structure
Open this publication in new window or tab >>X-ray Absorption Spectroscopy on Nano-Magnet Arrays and Thin Films: Magnetism and Structure
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The magnetic and structural properties of nano magnet arrays and ferromagnetic thin films are investigated. Circular x-rays are used and extensive use is made in this Thesis of the X-ray Magnetic Circular Dichroism (XMCD) technique. By means of the XMCD magneto-optic sum rules the values of the orbital and spin moments are determined. In the case of the nano magnet arrays studied, the XMCD technique is used in a spatially resolved mode using Photo Electron Emission Microscopy (PEEM) after circular light excitation. The Extended X-ray Absorption Fine Structure (EXAFS) is studied in both the Co K- and L-edges.

In situ Co L-edge X-ray XMCD spectroscopy measurements are presented, in combination with spectro-microscopy results, on Co/Pt and Co/Au based nano-dot arrays, of typical dot lateral size 250×100 nm2, on self organized Si0.5Ge0.5. The Co is only a few atomic layers thick. The dot arrays display a high degree of lateral order and the individual dots, in several cases, exhibit a stable magnetic moment at 300 K. It is found possible to characterize the spin reorientation of these dot arrays. For both systems the in- versus out-of-plane orbital moment anisotropy, is not always related with an out-of-plane magnetization and the occurrence of a spin reorientation. By performing Co K-edge EXAFS measurements the local atomic structure around the Co atoms is characterized. The feasibility of a high precision quantitative structural analysis of L-EXAFS is studied on the system Au/Co/Au/W(110). The spin reorientation transition is studied as a function of the Co thickness and Au cap thickness. The L-edge EXAFS indicates that this reorientation is correlated to a lattice expansion in the perpendicular direction.

High precision angle dependent XMCD work is performed on a high temperature exchange bias system. Pinned or frozen magnetic moments are studied within an exchange biased NiFe ferromagnet at the NiFe/FeMn, ferromagnet/antiferromagnet interface by XMCD and complemented by x-ray resonant reflectivity experiments, at the Ni, Fe and Mn L-edges. The Mn L-edge XMCD MnSb and of (Ga, Mn)As layers modified by high temperature annealing is studied. For MnSb an enhanced value is obtained versus theoretical calculations. This result can be explained by means of the enhanced surface to volume ratio for the samples studied. For (Ga, Mn)As differences are found in the local environment of the Mn atoms upon annealing.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2010. 61 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 710
self organization, nano-magnet, xmcd, exafs, peem, magnetism
National Category
Condensed Matter Physics Condensed Matter Physics
Research subject
Physics of Matter
urn:nbn:se:uu:diva-112824 (URN)978-91-554-7712-7 (ISBN)
Public defence
2010-03-05, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Available from: 2010-02-11 Created: 2010-01-20 Last updated: 2011-07-08Bibliographically approved

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