http://perso.neel.cnrs.fr/olivier.fruchart/ http://perso.neel.cnrs.fr/olivier.fruchart/ Institut Néel, Grenoble, France. Magnetic domain walls in cylindrical nanowires – From opportunities for fundamental science towards 3D storage media? Institut NEEL Grenoble - France The research leading to these results has received funding from the European Unions's 7th Framework Programme under grant agreement n°309589 (M3d) O. Fruchart et al. Sincrotrone Elettra Trieste - Italy Friederich-Alexander Universität Erlangen-Nürnberg - Germany Smart Membranes GmbH Halle – Germany
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Olivier Fruchart – Seminar Labex NIE – Strasbourg, 27 May 2015 – p.3
Institut Néel, Grenoble, France http://perso.neel.cnrs.fr/olivier.fruchart/slides
Current technology for magnetic data storage
S. Takenoiri, J. Magn. Magn. Mater. 321, 562 (2009)
B. C. Stipe, Nature Photon. 4, 484 (2010)
Compromise : time stability, writability, readibilityRelies on progress of technology and science
Magnetic bits on Hard Disk Drive
Co-based hard disk media : bits 50nm and below
Underlying microstructure
Gains in areal density
500nm
Olivier Fruchart – Seminar Labex NIE – Strasbourg, 27 May 2015 – p.4
Institut Néel, Grenoble, France http://perso.neel.cnrs.fr/olivier.fruchart/slides
Hard disk drives over time – Cornerstones
1956 RAMAC, IBM, first HDD
19981986 Discovery of GMR GMR in read heads
Olivier Fruchart – Seminar Labex NIE – Strasbourg, 27 May 2015 – p.5
Institut Néel, Grenoble, France http://perso.neel.cnrs.fr/olivier.fruchart/slides
Growth rate is seriously slowing downMajor bottlenecks aheadAny 2D-based storage design will sooner or later face a limit in areal density, imposer by fundamental bottlenecks
Olivier Fruchart – Seminar Labex NIE – Strasbourg, 27 May 2015 – p.27
Institut Néel, Grenoble, France http://perso.neel.cnrs.fr/olivier.fruchart/slides
Flat strips
Generalized phase diagram – From strips to wires
Motivation :Provide a unified picture of domain walls in (nearly) one-dimensional systems
Transverse and vortex
Cylindrical wires
Transverse and Bloch-point walls
Confusion between Bloch-point and vortex
Emergence of square or rectangular wires
P. Sergelius et al., Nanotech. 25,504002 (2014)Top-down + bottom-up / Planar templates
Open issues
400nm Span strips to wiresClear and simple classificationMay Bloch-point walls be found in rectangular wires ?
Olivier Fruchart – Seminar Labex NIE – Strasbourg, 27 May 2015 – p.28
Institut Néel, Grenoble, France http://perso.neel.cnrs.fr/olivier.fruchart/slides
Generalized phase diagram – From strips to wiresTopology of the transverse – vortex wall family
Square side : 30nm Square side : 44nm
Transverse and vortex walls share topology
May be shortened to 'vortex' or 'transverse' if dominating feature
Do not use 'vortex' for 'Bloch-point'
Review chapter : S. Jamet et al., in Magnetic Nano- and Microwires: Design, synthesis, properties and applications, M. Vázquez Ed., Woodhead, in press. (arXiv:1412.0679)
Olivier Fruchart – Seminar Labex NIE – Strasbourg, 27 May 2015 – p.29
Institut Néel, Grenoble, France http://perso.neel.cnrs.fr/olivier.fruchart/slides
Circulation of magnetization Quantify curling→
Imaging the general character of curling
Quantify curling in the Transverse/Vortex wall
Transverse
/Vortex
End domain Bloch-Point wall Diameter modulation
divM≈−dM z
d z
Driving force for curling :spread volume charges
z
Transverse
Second-order transition for D≈7Δd
Olivier Fruchart – Seminar Labex NIE – Strasbourg, 27 May 2015 – p.30
Institut Néel, Grenoble, France http://perso.neel.cnrs.fr/olivier.fruchart/slides
Review chapter : S. Jamet et al., in Magnetic Nano- and Microwires: Design, synthesis, properties and applications, M. Vázquez Ed., Woodhead, in press. (arXiv:1412.0679)
Extensive coverage of the width/thickness space
Bloch-point walls should exist away from disk or square cross-section
Olivier Fruchart – Seminar Labex NIE – Strasbourg, 27 May 2015 – p.31
Institut Néel, Grenoble, France http://perso.neel.cnrs.fr/olivier.fruchart/slides
Simulations
Experiments
Quantify domain wall length
500nm
Diameter 95nm
WireWire
Shadow
Diameter 70nm
Wire
Shadow
Sharp increase of lengthwith diameter
Analytics
Physics : balance exchange and dipolar energies
Energy : E ∼AR2 /Δd Wall length :L∼R2 /Δd
Confirmation of scaling law for wall length L∼R2 /ΔdReview chapter : S. Jamet et al., in Magnetic Nano- and Microwires: Design, synthesis, properties and applications, M. Vázquez Ed., Woodhead, in press. (arXiv:1412.0679)