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Optimierung des Schaltvorgangs in mesoskopischen magnetischen Strukturen

English title Optimizing magnetization switching in mesoscopic magnetic structures
Applicant Raabe Jörg
Number 125039
Funding scheme Project funding (Div. I-III)
Research institution Paul Scherrer Institut
Institution of higher education Paul Scherrer Institute - PSI
Main discipline Condensed Matter Physics
Start/End 01.09.2010 - 31.08.2013
Approved amount 245'315.00
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Keywords (17)

data storage; switching; XMCD; vortex; PolLux; Swiss Light Source; Paul Scherrer Institut; thin film; permalloy; electron beam lithography; genetic algorithm; magnetism; nano-scale materials; x-rays; data storage; microscopy; materials science

Lay Summary (English)

Lead
Lay summary
Magnetic bits are used for data storing. Depending on their orientation (up or down) they represent a bit (1 or 0). Understanding and optimizing how such magnetic bits are switched is important for advancing magnetic data storage.We study magnetic platelets of about 0.001mm diameter containing a vortex. This is a tiny region (~10 nm) where the magnetic field points either into or out-of the plane (1 or 0). The orientation of the magnetic field is measured using x-ray magnetic circular dichroism (XMCD). These vortices can be switched by applying a magnetic field pulse. Varying the strength, direction, duration and shape of the pulse we attempt to optimize the switching, i.e minimize the time and energy needed, while maximizing the switching probability.The experiments use an x-ray microscope (PolLux) at the Swiss Light Source, Paul Scherrer Institut. Samples are thin film structures (circles, rectangles, ellipses) fabricated out of a soft magnetic material (permalloy) using electron beam lithography.For optimization we use a genetic algorithm where initially a large number of random magnetic field pulses are tested. Those pulses most successful in inducing switching are taken into the next iteration (survival of the fittest) and are partially mixed amongst each other (cross-breeding) and partially randomly modified (mutation). After a large number of iterations (generations) the optimum pulse shape should have evolved. This will be done for a large range of sizes, shapes, materials of the magnetic platelets to understand the mechanisms limiting the switching.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
A single probe for imaging photons, electrons and physical forces
Pilet Nicolas, Lisunova Yuliya, Lamattina Fabio, Stevenson Stephanie E., Pigozzi Giancarlo, Paruch Patrycja, Fink Rainer H., Hug Hans J., Quitmann Christoph, Raabe Joerg (2016), A single probe for imaging photons, electrons and physical forces, in NANOTECHNOLOGY, 27(23), 235705.
Nanoscale switch for vortex polarization mediated by Bloch core formation in magnetic hybrid systems
Wohlhueter Phillip, Bryan Matthew Thomas, Warnicke Peter, Gliga Sebastian, Stevenson Stephanie Elizabeth, Heldt Georg, Saharan Lalita, Suszka Anna Kinga, Moutafis Christoforos, Chopdekar Rajesh Vilas, Raabe Joreg, Thomson Thomas, Hrkac Gino, Heyderman Laura Jane (2015), Nanoscale switch for vortex polarization mediated by Bloch core formation in magnetic hybrid systems, in NATURE COMMUNICATIONS, 6, 7836.
Topologically confined vortex oscillations in hybrid [Co/Pd](8)-Permalloy structures
Heldt Georg, Bryan Matthew T., Hrkac Gino, Stevenson Stephanie E., Chopdekar Rajesh V., Raabe Joerg, Thomson Thomas, Heyderman Laura J. (2014), Topologically confined vortex oscillations in hybrid [Co/Pd](8)-Permalloy structures, in APPLIED PHYSICS LETTERS, 104(18), 182401.
Dynamic stabilization of nonequilibrium domain configurations in magnetic squares with high amplitude excitations
Stevenson S.E., Moutafis C., Heldt G., Chopdekar R.V., Quitmann C., Heyderman L. J., Raabe J. (2013), Dynamic stabilization of nonequilibrium domain configurations in magnetic squares with high amplitude excitations, in PHYSICAL REVIEW B, 87(5), 054423.
Direct observation of antiferromagnetically oriented spin vortex states in magnetic multilayer elements
Wintz S, Strache T, Korner M, Fritzsche M, Marko D, Monch I, Mattheis R, Raabe J, Quitmann C, McCord J, Erbe A, Fassbender J (2011), Direct observation of antiferromagnetically oriented spin vortex states in magnetic multilayer elements, in APPLIED PHYSICS LETTERS, 98(23), 232511-232511.
Nanostructure characterization by a combined x-ray absorption / scanning force microscopy system
Pilet Nicolas, Raabe Joerg, Stevenson Stephanie E., Romer Sara, Bernard Laetitia, McNeill Christopher R., Fink Rainer H., Hug Hans J., Quitmann Christoph, Nanostructure characterization by a combined x-ray absorption / scanning force microscopy system, in Nanotechnology, 23(47), 475708.

Collaboration

Group / person Country
Types of collaboration
Forschungszentrum Dresden / Rossendorf Germany (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Exchange of personnel

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Third Joint Users’ Meeting at PSI Poster Dynamic stabilization of nonequilibrium domain configurations in magnetic squares with high amplitude excitations 18.09.2013 Villigen - PSI, Switzerland Raabe Jörg; Stevenson Stephanie Elizabeth;
Annual Meeting of the Swiss Phyical Society Poster Dynamic stabilization of nonequilibrium domain configurations in magnetic squares with high amplitude excitations 03.09.2013 Linz, Austria Raabe Jörg; Stevenson Stephanie Elizabeth;
Joint European Magnetic Symposia JEMS 2012 Talk given at a conference Magnetisation dynamics in mesoscopic structures studied with x-ray microscopy 09.09.2012 Parma, Italy, Italy Raabe Jörg; Stevenson Stephanie Elizabeth;


Associated projects

Number Title Start Funding scheme
150632 Ion Miller for Magnetic Nanostructures Research with Large Facilities 01.03.2014 R'EQUIP
137509 Novel exchange-coupled composite nanomagnets 01.06.2012 Project funding (Div. I-III)
172517 Topological multilayer spin textures for nanoscale magnon emission and propagation 01.03.2018 Project funding (Div. I-III)

Abstract

Magnetic structures with micron and sub-micron dimensions have properties different from anything we know in the macroscopic world. Because their dimensions are larger but comparable to the quantum mechanical exchange length, their magnetic configuration is simple and can fully be controlled by their size, shape and material: they are mesoscopic.Such particles are the basis for modern data storage in the computer industry. In each write step their configuration is switched from one stable state (1) to another (0). Switching of the magnetization is a non-linear and potentially chaotic process; the details and the underlying mechanisms are poorly understood and hotly debated in the literature.We suggest using x-ray microscopy to image the switching process with sub-micron spatial and sub-nanosecond temporal resolution. We will first identify magnetic eigenmodes of the mesoscopic structures. To switch the magnetization we will then resonantly (sine wave) excite such modes, a subsequent short field burst (single or few cycle pulse) will then induce switching.Our understanding of the physics of such mesoscopic magnetic structures and their eigenmodes will allow optimization of the switching in terms of speed and energy consumption as well as long term stability. The experiments will be accompanied by micromagnetic simulations helping to interpret the results.We request funding for a PhD student. The student will become part of the team already working successfully on magnetization dynamics at the Swiss Light Source (SLS). He/she will collaborate with specialists in nano-fabrication at Paul Scherrer Institut (PSI) and with colleagues preparing samples in different collaborating universities. The academic host institution will be ETH-Zürich.For the generation of switching pulses of arbitrary shape and duration we request funding of an arbitrary waveform generator (bandwidth >7.5 GHz).The emphasis of the project is on understanding the dynamics of mesoscopic magnetic structures, but it may as well produce know-how for applications. Initially conventional materials like permalloy will be used, because these provide extremely well controllable magnetic properties and can be switched reproducibly. Once proven successful, the project can be extended to more advanced materials and effects like spin torque switching. Furthermore, the question lends itself to application of advanced optimization methods like genetic algorithms, allowing optimization in complex multi parameter space.The investigations will profit from the planned performance upgrade of the SLS and ongoing improvements in x-ray optics which will provide ~10 ps temporal resolution (low alpha-mode) and sub 10 nm spatial resolution in the near future.
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