Reversible temperature-driven domain transition in bistable Fe magnetic nanostrips grown on Ru(0001)

A. Quesada, M. Monti, I. P. Krug, N. Rougemaille, F. Nickel, D. M. Gottlob, H. Doganay, A. T. N’Diaye, G. Chen, A. Serrano, K. F. McCarty, J. F. Fernández, C. M. Schneider, A. K. Schmid, and J. de la Figuera

Phys. Rev. B 92, 024416 – Published 15 July 2015

Abstract

High-aspect-ratio Fe nanostrips are studied with real-space micromagnetic imaging methods. We experimentally demonstrate reversible switching from essentially homogeneous single-domain states at room temperature to multidomain diamond states at elevated temperature. This temperature-dependent magnetic bistability can be understood and modeled by accounting for the temperature dependence of the magnetocrystalline, shape, and magnetoelastic anisotropies. These results show how the transition temperature between two magnetic domain states can be tailored by controlling epitaxial strain and particle geometry, which may generate new opportunities for magnetic memory and logic device design.

Received 27 April 2015
Revised 29 June 2015

DOI:https://doi.org/10.1103/PhysRevB.92.024416

Authors & Affiliations

A. Quesada^1,*, M. Monti², I. P. Krug^3,4, N. Rougemaille^5,6, F. Nickel³, D. M. Gottlob³, H. Doganay³, A. T. N’Diaye⁷, G. Chen⁸, A. Serrano¹, K. F. McCarty⁹, J. F. Fernández¹, C. M. Schneider³, A. K. Schmid⁸, and J. de la Figuera²

¹Instituto de Cerámica y Vidrio, CSIC, 28049 Madrid, Spain
²Instituto de Química Física “Rocasolano,” CSIC, 28006 Madrid, Spain
³Research Center Jülich GmbH, Peter Grünberg Institute PGI 6, JARA FIT, D-52425 Jülich, Germany
⁴Institute for Optics und Atomic Physics, Technical University Berlin, D-10632 Berlin, Germany
⁵CNRS, Institut NÉEL, F-38042 Grenoble, France
⁶Université Grenoble Alpes, Institut NÉEL, F-38042 Grenoble, France
⁷Lawrence Berkeley National Laboratory, Advanced Light Source, Berkeley, California 94720, USA
⁸Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
⁹Sandia National Laboratories, Livermore, California 94550, USA

^*Author to whom all correspondence should be addressed: a.quesada@icv.csic.es

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Vol. 92, Iss. 2 — 1 July 2015

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Images

Figure 1
(a), (b) XMCD-PEEM gray scale images ( $11 μ m$ field of view) at the $L_{3}$ x-ray absorption edge, where pixel brightness is proportional to the magnitude of the component of the magnetization vector along the incident photon beam direction. Imaging the same area at (a) 300 K and (b) 750 K shows temperature-dependent transition of several nanostrips from essentially single-domain C states to diamond multidomain states. oommf micromagnetic simulations show corresponding local spin directions of the single-domain C state (c) and the diamond multidomain state (d) (photon direction indicated by arrow/symbol in upper right corners).
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Figure 2
(a) Microspectroscopy from an individual nanostrip (x-ray absorption shown in red). Dichroic spectra (in blue) from a nanostrip show that the Fe $L_{3}$ edge has a shape corresponding to elemental Fe, rather than to an iron oxide. (b) shows dichroic spectra at the Fe $L_{3}$ edge corresponding to $F e_{3} O_{4}$ (reproduced from Ref. [26], with permission). (c) LEEM image ( $20 μ m$ field of view) showing the formation of nanowires on $Ru (0001)$ and highlighting the $60^{\circ} + / - 5^{\circ}$ angles between relative orientations of strips and the $+ / - 5^{\circ}$ angles between the strips and the underlying compact directions of the sketched hexagonal $Ru (0001)$ . (d) Microdiffraction from an individual nanostrip. The sum of a series of LEED patterns collected at different energies (from 15 to 50 eV) shows fixed diffraction spots from flat parts of the surface as well as streaks due to a family of diffraction spots that move as a function of energy. The moving diffraction spots originate from edge facets. The red arrow indicates the long axis direction of the nanostrip, perpendicular to the lines of motion of the streaked LEED spots.
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Figure 3
(a) Plot summarizing domain state measurements on nanostrips as a function of temperature and width. Red/blue triangle symbols indicate experimentally observed multidomain/single-domain configurations, respectively. Yellow star symbols indicate the transition critical width calculated from micromagnetic simulations, in good agreement with the experimental data. Two XMCD-PEEM images ( $6 μ m \times 4 μ m$ field of view) are inserted to highlight each state. (b) Internal energy as a function of temperature calculated by micromagnetic simulations corresponding to single- and multidomain configurations for nanostrips with three different widths (472, 336, and 268 nm) and constant aspect ratio of 8.
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