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Spin structures in micro-patterned highly spin-polarized materials

Mathias Kläui 1Mikhail Fonin 1Dirk Backes 1,2Christine Hartung 1Alexander Biehler 1Lutz Heyne 1Aranxta Fraile-Rodriguez 2Frithjof Nolting 2Laura Heyderman 2Andrea Locatelli 3Onur Mentes 3

1. Universität Konstanz, Universitätsstr. 10, Konstanz 78457, Germany
2. Paul Scherrer Institut (PSI), WLGA, Villigen PSI 5232, Switzerland
3. Sincrotrone Trieste, Basovizza 34012, Italy


Highly spin-polarized materials have become the focus of intense research due to their possible applications in spintronic devices and their exciting magnetotransport properties [1]. 100% spin-polarized materials where the density of states exhibits a gap in one spin channel, are commonly called half-metallic ferromagnets and one of the most prominent examples is magnetite (Fe3O4) [2].

Spin-dependent transport properties are in general strongly dependent on the spin polarization but in the usual geometry (multilayer pillar elements), interfaces can play a crucial role for magnetoresistance and spin transfer torque effects and often the polarization at interfaces is strongly reduced compared to the bulk value.

In order to make use of the high bulk spin polarization for spin transfer torque effects, single layer elements can be used, where the complications of interfaces are avoided. In such single layer elements, the interplay between currents and domain-walls leads to domain-wall magnetoresistance [3] and strong currents have been predicted to displace domain walls due to the spin transfer torque effect [3,4].

Before such devices can be envisaged, the spin structures of the domain walls has to be determined. We use high resolution X-ray magnetic circular dichroism photoemission electron microscopy to image the spin structure in highly spin - polarized magnetite (Fe3O4) patterned elements. Due to the cubic anisotropy, the domain wall spin structures strongly differ from those usually observed in permalloy [5]. In addition to head-to-head domain walls, also 90° domain walls are observed and the exact spin structure depends on the orientation of the magnetization with respect to the magnetocrystalline anisotropy axes.

[1] K. Dörr, J. Phys. D 39, R125 (2006).

[2] M. Fonin et al., J. Phys. Cond. Mat. (in press 2007)

[3] C. H. Marrows, Adv. Phys. 54, 585 (2005)

[4] M. Kläui et al., PRL 94, 106601 (2005)

[5] M. Laufenberg et al., APL 88, 52507 (2006)


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Presentation: Poster at E-MRS Fall Meeting 2007, Symposium I, by Mathias Kläui
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-05-04 12:34
Revised:   2009-06-07 00:44