O. Fruchart 1 1. SPINTEC, Univ. Grenoble Alpes / CNRS / CEA-INAC, France 2. Institut NÉEL, Univ. Grenoble Alpes / CNRS, France www.spintec.fr email: olivier.fruchart@cea.fr Slides: http://fruchart.eu/slides Curvilinear magnetism – Київ , Україна – 23-24 May 2019
Note: 3D devices make the decision! Fundamentals: curved and 3D magnetism K. T. Park et al., IEEE J. Sol. State Circuits 50 (1), 204 (2015) Dreams for a 3D storage device R. Streubel, J.Phys.D: Appl.Phys. 49, 363001 (2016) S. S. P. Parkin, Science 320, 190 (2008) + patents (IBM) A. Fernandez-Pacheco, Nat. Comm. 8, 15756 (2017) Olivier FRUCHART 23 May 2019 Domain wall motion in cylindrical nanowires Curvilinear magnetism – Київ, Україна
HDD: staggering areal density Technologies go 3D blog.dshr.org | www.insic.org SSD HDD vs Flash Cross-over in 2016 1Gb/mm2 → 600Gb/in2... 24-layer 3D NAND Flash Magnetic mass storage may only K. T. Park et al., remain for niche applications IEEE J. Sol. State Circuits 50 (1), 204 (2015) Olivier FRUCHART 23 May 2019 Domain wall motion in cylindrical nanowires Curvilinear magnetism – Київ, Україна
Field-driven case Current-driven case M. Hayashi et al., PRL 98, 037204 (2007) G. S. D. Beach et al., Nat. Mater 4, 741 (2005) Physics: dynamic transformation of domain walls Average speed does not exceed much 100 m/s Olivier FRUCHART 23 May 2019 Domain wall motion in cylindrical nanowires Curvilinear magnetism – Київ, Україна
Dzyaloshinskii-Moriya interaction Ferrimagnetic materials + Spin-Hall currents Field-driven Kim et al., Nat. Mater. 16, 1187 (2017) I.. M. Miron et al., Nat. Mater. 10, 419 (2011) A. Thiaville et al., EPL100, 57002 (2012) Current-driven Is direct spin-transfer in ferromagnets not compatible with fast DW motion? L. Caretta et al., Nat. Nanotech. 13, 1154, (2018) Olivier FRUCHART 23 May 2019 Domain wall motion in cylindrical nanowires Curvilinear magnetism – Київ, Україна
Motivation Domain walls in wires Expectations Olivier FRUCHART 23 May 2019 Domain wall motion in cylindrical nanowires Curvilinear magnetism – Київ, Україна
DOMAIN WALLS IN CYLINDERS What is a Bloch point? Topology of domain walls in 1D Transverse Vortex Néel Bloch Magnetization texture with local vanishing of magnetization R. Feldkeller, Z. Angew. Physik 19, 530 (1965) W. Döring, Transverse-Vortex (TVW) Bloch-point (BPW) J. Appl. Phys. 39, 1006 (1968) H. Forster, JAP91, 6914 (2002); A. Thiaville, Spin dynamics in confined magnetic structures III, 101, (2006). Review : S. Jamet, in Magnetic Nano- and Microwires, M. Vázquez Ed., Woodhead (2015) (arXiv:1412.0679) Transverse and vor ortex wall lls for or IP IP have same top opology: subject to o Walk lker fie field ld Blo Bloch-poin int walls lls have e a dif ifferent top opology Olivier FRUCHART 23 May 2019 Domain wall motion in cylindrical nanowires Curvilinear magnetism – Київ, Україна
BLOCH-POINT WALLS DYNAMICS LLG equation d𝐧 d𝑢 = − 𝛿 0 𝐧 × 𝐈 + 𝛽𝐧 × d𝐧 d𝑢 ‘Once - only’ Walker event Magnonic limit Tubes (similar to wires) H H R. Hertel, JPCM 28, 483002 (2016) Br Broad th theoreti tical l back ckground Locked Unstable A. Thiaville, Spin dynamics No o exp xperimental rep eport in confined magnetic structures III, (2006) Olivier FRUCHART 23 May 2019 Domain wall motion in cylindrical nanowires Curvilinear magnetism – Київ, Україна
MOTION OF WALLS UNDER CURRENT LLG equation d𝐧 d𝑢 = − 𝛿 0 𝐧 × 𝐈 + 𝛽𝐧 × d𝐧 d𝑢 − 𝐯 ∙ 𝛂 𝐧 + 𝛾𝐧 × 𝐯 ∙ 𝛂 𝐧 Precession Damping Adiabatic Non-adiabatic Strips: Walker breakdown Cylinders: no Walker 𝑤 𝑡𝑢𝑓𝑏𝑒𝑧 ~ 𝛾 BPW 𝛽 𝐾 velocity velocity 𝑤 𝑥𝑏𝑚𝑙𝑓𝑠 ∝ 𝐾 TVW BPW TW current current W=0 W=∞ W R. Wieser et al., Phys. Rev. B 82, 144430 (2010) Magnetically-soft materials: 𝛾 > 𝛽 Olivier FRUCHART 23 May 2019 Domain wall motion in cylindrical nanowires Curvilinear magnetism – Київ, Україна
Motivation Domain walls in wires Expectations Synthesis Olivier FRUCHART 23 May 2019 Domain wall motion in cylindrical nanowires Curvilinear magnetism – Київ, Україна
Standard Diameter engineering Anodization of aluminum -> template Atomic layer deposition to reduce inner diameter at constant pitch S. Da Col et al., APL 98, 112501 (2011) H. Masuda, Science 268, 1466-1468 (1995) Sequences of anodization/ALD/etching Electroplating -> Magnetic wires Simple metals and alloys : Co, Ni, S. Bochmann, JAP 124, 163907 (2018) Fe 20 Ni 80 , Co 20 Ni 80 Pulsed anodization S. Da Col et al., APL 98, 112501 (2011) Olivier FRUCHART 23 May 2019 Domain wall motion in cylindrical nanowires Curvilinear magnetism – Київ, Україна
Motivation Identify walls Domain walls in wires Expectations Synthesis Olivier FRUCHART 23 May 2019 Domain wall motion in cylindrical nanowires Curvilinear magnetism – Київ, Україна
XMCD-PEEM TECHNIQUE X-Ray Magnetic Circular Dichroism Photo-Emission Electron Microscopy Element selectivity Magnetic sensitivity Synchrotron-based Secondary electrons -> surface sensitive 25nm resolution in best case Olivier FRUCHART 23 May 2019 Domain wall motion in cylindrical nanowires Curvilinear magnetism – Київ, Україна
IMAGE BOTH WIRES AND SHADOW Locate walls Image domain walls FeNi FeNi Beam along wire Beam across wire Non-trivial patterns Need for modeling Olivier FRUCHART 23 May 2019 Domain wall motion in cylindrical nanowires Curvilinear magnetism – Київ, Україна
MODELING SHADOW XMCD-PEEM SHADOW XMCD-PEEM SIMULATION OF CONTRAST Example: Bloch-point wall S. Jamet et al., PRB92, 144428 (2015) Olivier FRUCHART 23 May 2019 Domain wall motion in cylindrical nanowires Curvilinear magnetism – Київ, Україна
TWO WALL TOPOLOGIES OBSERVED Bloch-point walls Transverse walls Experiment Experiment Simulation Simulation WIRE SHADOW Breaking of symmetry Orthoradial curling Symmetry with respect to Also imaged with electron plane perpendicular to axis holography: N. Bizière et al., Nanolett. 13, 2053 (2013) S. Da-Col et al., Phys. Rev. B (R) 89, 180405, (2014) Olivier FRUCHART 23 May 2019 Domain wall motion in cylindrical nanowires Curvilinear magnetism – Київ, Україна
Motivation Identify walls Domain walls in wires Move walls under field Expectations Synthesis Olivier FRUCHART 23 May 2019 Domain wall motion in cylindrical nanowires Curvilinear magnetism – Київ, Україна
MOVE DOMAIN WALLS - QUASISTATICS FeNi Material improvement – Annealing Quasistatic motion fcc[111] SEM fcc[200] Larger gr La grain in si size AFM Less Less strain di distributio ion MFM Pinning field and density decreased S. Da-Col, Appl. Phys. Lett. 109, 062406 (2016) TEM – No clear correlation with structure M. Staňo et al., J. Phys. Conf. Series (2017) B. Trapp, in preparation Pioneering with MFM: Y. Henry et al., EPJB 20, 35 (2001) Olivier FRUCHART 23 May 2019 Domain wall motion in cylindrical nanowires Curvilinear magnetism – Київ, Україна
DYNAMICS – SELECTION OF CIRCULATION CoNi Modulated diameter to keep domain walls in wire Focus on wire Focus on shadow Selection of circulation (to be confirmed) Not ot a 100 100% cor orrelation Final Initial Field pulse Field pulse Olivier FRUCHART 23 May 2019 Domain wall motion in cylindrical nanowires Curvilinear magnetism – Київ, Україна
DYNAMICS – DOMAIN WALL TRANSFORMATION BPW CW BPW CW TW Initialized +16mT +16mT TW BPW CCW TW -16mT -16mT THE DARK SIDE BPW CCW TW Fe 20 Ni 80 , 140nm -24mT BPW CW 2µm BPW CW +12mT +12mT BPW CCW Initialized +16mT Switch circulation -16mT BPW CW BPW CW No topological TW protection +24mT -12mT -12mT A. Wartelle, PRB99, 024433 (2019) Olivier FRUCHART 23 May 2019 Domain wall motion in cylindrical nanowires Curvilinear magnetism – Київ, Україна
DW TRANSFORMATION - SIMULATIONS How does topology change? Position Topological number BPW TVW Parametric model Driv Driven by y dy dynamics TVW -> BP BPW: induction tube twis ists s and un an unwinds BP BPW -> TVW: sti till ll un unclear Simulations Op Opens com omputatio ional an and material scie science ch challe lenges A. Wartelle, PRB99, 024433 (2019) Olivier FRUCHART 23 May 2019 Domain wall motion in cylindrical nanowires Curvilinear magnetism – Київ, Україна
Motivation Identify walls Domain walls in wires Move walls under field Expectations Move walls under current Synthesis Olivier FRUCHART 23 May 2019 Domain wall motion in cylindrical nanowires Curvilinear magnetism – Київ, Україна
Recommend
More recommend
