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Investigation of interface properties of Ni/Cu multilayers by high kinetic energy photoelectron spectroscopy
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
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2009 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 80, no 9, 094104Article in journal (Refereed) Published
Abstract [en]

High kinetic-energy photoelectron spectroscopy (HIKE) or hard x-ray   photoelectron spectroscopy has been used to investigate the alloying of   Ni/Cu (100) multilayers. Relative intensities of the corelevels and   their chemical shifts derived from binding energy changes are shown to   give precise information on physicochemical properties and quality of   the buried layers. Interface roughening, including kinetic properties   such as the rate of alloying, and temperature effects on the processes   can be analyzed quantitatively. Using HIKE, we have been able to   precisely follow the deterioration of the multilayer structure at the   atomic scale and observe the diffusion of the capping layer into the   multilayer structure which in turn is found to lead to a segregation in   the ternary system. This is of great importance for future research on   multilayered systems of this kind. Our experimental data are   supplemented by first-principles theoretical calculations of the   core-level shifts for a ternary alloy to allow for modeling of the   influence of capping materials on the chemical shifts.

Place, publisher, year, edition, pages
2009. Vol. 80, no 9, 094104
Keyword [en]
ab initio calculations, alloying, chemical shift; copper, diffusion, interface structure, magnetic multilayers, nickel, X-ray photoelectron spectra
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-108327DOI: 10.1103/PhysRevB.80.094104ISI: 000270383000027OAI: oai:DiVA.org:uu-108327DiVA: diva2:235387
Available from: 2009-09-15 Created: 2009-09-15 Last updated: 2017-01-16Bibliographically approved
In thesis
1. New Materials for Spintronics: Electronic structure and magnetism
Open this publication in new window or tab >>New Materials for Spintronics: Electronic structure and magnetism
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Materials exhibiting new functionalities due to interdependent electric (e.g. conductivity) and magnetic properties are potentially interesting for spintronics applications. We have investigated electronic and magnetic properties by means of x-ray spectroscopies and SQUID magnetometry in several magnetic materials, often in the form of thin films, which have shown promising properties for applications.

One of the main subjects has been studies of inter-diffusion between layers in multilayer structures, which is an important factor for spin-dependent transport and magnetic properties. These studies have been performed by high kinetic (HIKE) photoemission spectroscopy where high photon energies increase the bulk sensitivity in comparison to soft x-ray photoemission spectroscopy. Cu/Ni multilayers were studied mainly as a model system and revealed a diffusion process that was dependent on layer thicknesses and capping materials. CoFeB/MgO/CoFeB, which is used as a magnetic field sensor in hard drives, has recently been shown to exhibit a perpendicular magnetic anisotropy (PMA) switchable by electric fields. We have studied both the interface quality and magnetic properties of thin CoFeB layers exhibiting PMA. Layered structures of full Heusler alloys Co2MnGe/Rh2CuSn have been proposed as a promising candidate for current-perpendicular-to-plane giant magneto-resistance sensors. Using HIKE,we have shown that diffusion of atoms, mainly Mn, occurs at temperatures lower than what is used in device fabrication, which likely contributes to the limited magneto-resistance values obtained.

Lately, a large body of research has been performed on semiconductors doped with transition metal elements with the hope to find a ferromagnetic semiconductor at room temperature, a foundation for new devices combining spin and charge in their functionality. We have investigated Co and Fe doping in ZnO for different concentrations of the dopants and different annealing temperatures. The Co and Fe atoms are shown to forms clusters for which antiferromagnetic interactions are dominating.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. 66 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 897
Keyword
Spintronics, X-ray photoemission, XPS, XMCD, XAS, magnetic semiconductors, HIKE, HAXPES, multilayer, monte carlo, magnetism
National Category
Condensed Matter Physics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-167415 (URN)978-91-554-8275-6 (ISBN)
Public defence
2012-03-16, Polhemsalen, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2012-02-24 Created: 2012-01-27 Last updated: 2012-09-18Bibliographically approved

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Knut, RonnyMarcellini, MorenoAndersson, GabriellaSvensson, SvanteKaris, Olof

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