Scanning tunneling microscopy observations of single-crystal Fe∕ MgO∕ Fe magnetic tunnel junctions

Department of Materials Engineering Science, Graduate School of Engineering Science, Core Research for Evolutional Science and Technology (CREST), Osaka University, 560-8531, Toyonaka, Osaka, Japan; Japan Science and Technology Agency, 332-0012, Kawaguchi, Saitama, Japan; Core Research for Evolutional Science and Technology (CREST), NanoElectronics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 305-8568, Tsukuba, Ibaraki, Japan; Japan Science and Technology Agency, 332-0012, Kawaguchi, Saitama, Japan
Journal of Applied Physics (Impact Factor: 2.19). 04/2006; 99(8). DOI: 10.1063/1.2170069

ABSTRACT Scanning tunneling microscopy observations of a single-crystal Fe001 / MgO001 /Fe001 magnetic tunnel junction which shows a large tunnel magnetoresistance effect were performed. Step-and-terrace structures of an epitaxial MgO barrier layer, which are very similar to surfaces of a bottom Fe underlayer, were observed. This indicates that the MgO terraces were grown flatly on each terrace of the Fe electrode. It is supposed that these atomically flat terraces enable a coherent tunneling of electrons through magnetic tunnel junctions. © 2006 American Institute of Physics.

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    ABSTRACT: Using ultrahigh vacuum high resolution scanning probe microscopy, we investigated the growth and magnetic properties of epitaxial Fe films grown on MgO(001) at different substrate deposition temperatures. On room temperature substrates, Fe forms interconnected grains and for 14 nm films produce very large magnetic domains. The domain walls are comprised of a rich variety of Néel, Bloch, and cross ties with interesting characteristics. On high temperature substrates, Fe grows by pyramidal island formation, with well-defined single atomic step terraces. The magnetic properties are dependent on the film thickness, which determines the amount of exchange coupling between the islands. The magnetic structure varies from complex patterns at low coverage to well ordered magnetic ripples and domain walls at higher coverage. The detailed explanation will be shown in this paper.
    Journal of Applied Physics 05/2007; 101(9):09D123-09D123-3. · 2.19 Impact Factor
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    ABSTRACT: A calculation of the coherent and ballistic phonon transport via thin nanojunctions between bcc lattices is presented. The model system A/B/A consists of a finite number of bcc (001) atomic layers of an element B sandwiched between two bcc semi-infinite crystal lattices of another element A oriented in the same (001) plane. It is applied to the Fe/Co/Fe nanojunction and to the inverse Co/Fe/Co nanojunction. The theoretical calculations of the ballistic phonon transmission via the nanojunction are carried out using the matching method. The possible experimental measurements of this ballistic transmission in comparison with theoretical results should be a useful probe for the determination of alloying force constants across the interface between two such elements. The full bcc dynamics of this system is under study.

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