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The influence of the distribution of the inherent ordering temperature on the ordering in layered magnets
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
2009 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 79, no 14, 144426- p.Article in journal (Refereed) Published
Abstract [en]

We study the influence of gradients in the inherent ordering temperature of coupled layered magnets on the overall magnetic ordering. The gradients were accomplished by growing Fe(001) layers with thicknesses ranging from two to three monolayers, all separated by   seven monolayers of V(001). Two types of gradient superstructures were grown: one with the highest and one with the lowest inherent ordering temperature in the center of the samples. The superstructure with the thinnest outermost Fe layers exhibits lower ordering temperature,  demonstrating the importance of the sequence of the layers. Both these   structures order at temperatures significantly lower than a superlattice with a constant thickness of the Fe layers (three monolayers). The results highlight the intricate collective aspects of  the magnetic ordering in layered magnets, which are not captured by current models in magnetism research.

Place, publisher, year, edition, pages
2009. Vol. 79, no 14, 144426- p.
Keyword [en]
antiferromagnetic materials, ferromagnetic materials, iron, magnetic multilayers, monolayers, vanadium
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-96976DOI: 10.1103/PhysRevB.79.144426ISI: 000265943200088OAI: oai:DiVA.org:uu-96976DiVA: diva2:171730
Available from: 2008-04-02 Created: 2008-04-02 Last updated: 2015-03-10Bibliographically approved
In thesis
1. Magnetic Ordering in Layered Magnets
Open this publication in new window or tab >>Magnetic Ordering in Layered Magnets
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The preparation of layered magnets needs the knowledge of growth techniques which are focused on the growth of Fe/V(001) superlattices. Such films have been structurally investigated by X-rays reflectivity and diffraction.

The magnetic investigations have been carried out by magneto-optic Kerr effect (MOKE), Superconducting Quantum Interference Device (SQUID) magnetometry and polarized neutron reflectivity (PNR). This latter technique has been used in cooperation with the Institute Laue Langvin (Grenoble, France) and Ruhr Universität (Bochum, Germany).

The cross-over in universality class is shown in a series of layered magnets where a δ-doping layer of Fe has been embedded between two layers of Pd showing that the magnetization depends on the effective magnetic thickness of the polarized Pd. A model for the cross-over has been developed in terms of magnetic excitations.

The interlayer exchange coupling (IEC) mediated by a non-magnetic spacer has been reviewed focusing the attention on the recent theoretical and experimental works based on Fe/V(001) superlattices.

The IEC can be tailored at will by reversibly alloying of the spacer with H: this has been proved in Fe/V(001) double layers showing that in the two dimensional limit, the universality class is not affected by the coupling.

The magnetic order-disorder transitions in Fe/V(001) superlattices do not seem to belong to any universality class. A phenomenological model which accounts for the effective coupling at the boundaries has been developed.

The influence of the inherent ordering temperatures of single magnetic layers has been investigated in Fe/V(001) superlattices proving that the weakest ferromagnetic layer affects the overall magnetic ordering.

A new kind of layered magnet has been developed to increase the effect of the boundaries. PNR measurements show that the universality class depends on which length-scale is investigated.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2008. 88 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 418
Keyword
Physics, Magnetic thin films and superlattices, Magnetic phase transitions, Polarized neutron reflectometry, Fysik
Identifiers
urn:nbn:se:uu:diva-8604 (URN)978-91-554-7147-7 (ISBN)
Public defence
2008-04-24, Polhemssalen, Ångströmlaboratoriet, Lagerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2008-04-02 Created: 2008-04-02 Last updated: 2010-03-08Bibliographically approved

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Hjörvarsson, BjörgvinWolff, Maximilian

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