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216 results on '"Fruchart, O."'

55. Domain wall pinning in cylindrical nanowires with modulation in diameter: analytical and micromagnetic models

Author

Fernández-Roldán, José A., Gusakova, D., Toussaint, J., Pérez del Real, Rafael, Chubykalo-Fesenko, O., Fruchart, O., and Vázquez Villalabeitia, Manuel

Abstract

Poster presented at the International Magnetics Conference (INTERMAG Europe 2017), held in Dublin (Ireland) on April 24-28th, 2017., Magnetic nanowires (NWs) play an important role in several future technologies such as magnetic recording, magnetic sensors or bio applications [1]. Control over the magnetization is essential in technologies where reversal process takes place via nucleation/propagation and pinning/depinning of domain wall (DW). This concerns concepts such as race track memory or logic devices [2]. So far, for ease of fabrication and detection, research has been mostly focused on lithographically prepared nanostrips, where DWs can be artificially nucleated and subsequently pinned [3]. The use of cylindrical nanowires is the route towards 3D memory devices[4]. A renewed attention towards cylindrical nanowires is due to their specific characteristics which theoretically allow a larger variety of magnetic topologies for DWs than in nanostrips, particularly Bloch-point walls, or the absence of the Walker limit for the DW motion [5,6]. Recent studies have reported the domain structure and magnetization reversal in individual nanowires by experimental (e.g., MFM, MOKE, PEEMS/XRCD) methods and micromagnetic simulations [7,8]. The modeling shows that demagnetization process in these cases takes place by domain wall motion mechanisms. Cylindrical nanowires are typically grown by electrochemical route with designed diameter in the range 15 to 200 nm. Recently, NWs with tailored longitudinal modulations in diameter or compositionally multisegmented (multilayer) NWs have been fabricated and characterized. A particular objective of such modulations is to achieve control for motion and pinning of DWs to be shifted [9]. The understanding of the corresponding magnetization configuration and the DW pinning at the modulations are essential for the development of such novel technologies. Several types of magnetic domains can appear in NWs, namely, with longitudinal, transverse or circumferential magnetization. On the other hand, transverse or azimuthal vortex, (that is Bloch-point like), domain walls can be found. In the present study nanowires with different diameters and composition have been considered where transverse or vortex domain walls can be nucleated. We investigate particularly the influence of diameter modulations. Two kinds of cylindrical nanowires have been simulated by micromagnetics: i) FeCo NWs with fcc polycrystalline structure and diameter modulations between 40 and 130 nm, and ii) FeNi NWs with diameter modulations between 20 and 50 nm. Our results show that FeCo NWs are characterized by vortex magnetization configurations. Different vortex chiralities were obtained depending on the polycrystalline structure distribution. The switching field depends on the difference of segments diameter and the chirality of the nucleated DWs along the nanowire constrictions. Pinning of domain walls at the diameter transitions is analysed for given chirality patterns and diameter values. Figure 1 shows the hysteresis loops and the corresponding DW chiralities in the simulated NW with particular distribution of grain structure. In the case of FeNi nanowires transverse domain walls are formed. Here we provide a simple analytic model for the DW pinning at the diameter transition under a uniform applied field. A flat transverse DW is assumed creating magnetic charges uniformly confined within a sphere of the same radius as that of the NW and centered at the DW position. This model leads to a scaling law for the depinning field and pinning potential, which fairly agrees with the results obtained in the micromagnetic simulations. Figure 2 shows the final position of the DW for different applied fields, H, obtained from micromagnetic simulations and analytical model for a nanowire with diameters 20 and 10 nm. The dependence of the DW width with the modulation size (height and width) was also numerically studied.

Published
2017

57. Soft x-ray resonant magnetic reflectivity study of thin films and multilayers

Author

Tonnerre, J.M., Seve, L., Barbara-Dechelette, A., Bartolome, F., Raoux, D., Chakarian, V., Kao, C.C., Fischer, H., Andrieu, s., and Fruchart, O.

Subjects
X-rays -- Scattering, Magnetic resonance -- Usage, Thin films -- Magnetic properties, Physics
Abstract

The use of x-ray resonant magnetic scattering (XRMS) has been developed, particularly in the soft x-ray range, to measure resonant magnetic reflectivity on thin films and multilayers in a transverse geometry. All experimental characteristics of the angular and energy reflectivity curves have been reproduced, along with the asymmetry ratio. This was applied to FexMn(sub1-x) alloy films.

Published
1998

62. X-ray photoelectron emission microscopy in combination with x-ray magnetic circular dichroism investigation of size effects on field-induced Neel-cap reversal

Author

Cheynis, F., Rougemaille, N., Belkhou, R., Toussaint, J.-C., and Fruchart, O.

Subjects
Circular dichroism -- Analysis, Magnetic fields -- Analysis, Dielectric films -- Structure, Dielectric films -- Magnetic properties, Thin films -- Structure, Thin films -- Magnetic properties, X-ray microscopy -- Usage, Physics
Abstract

X-ray photoelectron emission microscopy in combination with x-ray magnetic circular dichroism is used for examining the effect of an applied magnetic field on Neel caps. The results have not shown any correlation between the value of the reversal field and geometrical features of the dots.

Published
2008

63. Magnetic properties of self-organized lateral arrays of (Fe, Ag)/Mo(110) nanostripes

Author

Borca, B., Fruchart, O., and Meyer, C.

Subjects
Iron compounds -- Chemical properties, Iron compounds -- Magnetic properties, Silver compounds -- Chemical properties, Silver compounds -- Magnetic properties, Molybdenum -- Chemical properties, Molybdenum -- Magnetic properties, Electrophoretic deposition -- Analysis, Physics
Abstract

Self-organized arrays of laterally alternating (Fe, Ag) nanostripes with a period of 3.5 nm were fabricated on Mo(110)/[Al.sub.2][O.sub.3](1120) by sequential deposition of Fe and Ag on Mo(110). The arrays were found to display a strong in-plane uniaxial anisotropy along [001], the directions of the wires, resulting from a balance between dipolar, interface and magnetoelastic anisotropy.

Published
2006

66. Magnetic properties of self-organized lateral arrays of (Fe,Ag)/Mo(110) nanostripes.

Author

Borca, B., Fruchart, O., and Meyer, C.

Subjects
*NANOSTRUCTURED materials, *MAGNETIC properties, *MAGNETISM, *IRON, *SILVER, *MOLYBDENUM
Abstract

We report the fabrication of self-organized arrays of Fe nanostripes with a lateral period of 3.5 nm by sequential deposition of Fe and Ag on Mo(110). The wires display a strong in-plane uniaxial magnetic anisotropy along their length and are superparamagnetic above TB=185±15 K. The large value of nucleation volumes, which is inferred from the analysis of the thermal dependence of coercivity below TB, suggests the existence of interactions between the wires. [ABSTRACT FROM AUTHOR]

Published
2006
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69. Magnetic field-induced domain wall motion in cylindrical nanowires

Author

Wartelle, A., primary, Thirion, C., additional, Afid, R., additional, Jamet, S., additional, Da Col, S., additional, Cagnon, L., additional, Toussaint, J., additional, Bachmann, J., additional, Bochmann, S., additional, Locatelli, A., additional, Mentes, T., additional, and Fruchart, O., additional

Published
2015
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71. XMCD-PEEM magnetic imaging beyond domains: internal degree of freedom in domain walls

Author

Cheynis, F, Masseboeuf, Aurélien, Fruchart, O, Toussaint, Jc, Rougemaille, N, Belkhou, R, Bayle-Guillemaud, P, Marty, A, Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), and Masseboeuf, Aurélien

Subjects
[PHYS]Physics [physics], ComputingMilieux_MISCELLANEOUS, [PHYS] Physics [physics]
Abstract

International audience

Published
2009

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