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PhD thesis, Claudiu Daniel Stanciu

PhD thesis, Claudiu Daniel Stanciu. Radboud University Nijmegen, The Netherlands (2004 - 2008) (now working at Océ Technologies). Over 110 years of Magnetic Recording. The first working magnetic recorder ( 1898 ). The first magnetic tape ( 1928 ). Telegraphone (by Valdemar Poulsen).

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PhD thesis, Claudiu Daniel Stanciu

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  1. PhD thesis, Claudiu Daniel Stanciu Radboud University Nijmegen, The Netherlands (2004 - 2008) (now working at Océ Technologies)

  2. Over 110 years of Magnetic Recording The first working magnetic recorder (1898) The first magnetic tape (1928) Telegraphone (by Valdemar Poulsen) Magnetophon (Fritz Pfleumer) The first hard disk drive – HDD (1955) The first magnetic core memory (late 1940’s) IBM 5MB memory storage (IBM)

  3. Magnetic Recording Devices Today The first hard disk drive – HDD (1955) 5MB memory storage (IBM) Hard disk drive – HDD (2010) 5GB memory storage

  4. Magnetic Bits 0 1 1 0 Magnetic domains in a HDD - black areas - white areas MagneticData Storage Hard Disk Drive(HDD)

  5. FAST! Challenges in Magnetic Data Storage Higher and higher bit density Higher and higher data storage speed SMALLER magnetic areas(tinier magnets) FASTER switching speedof the tiny magnets “By 2012, just two disks will provide the same storage capacity as the human brain!”Robert Birge (Syracuse University) ~ 10 Terabyte This thesis focuses on the speed of the magnetization switching

  6. How to Switch a Magnet…? ?

  7. Conventional Magnetic Data Storage The conventional way of reversing magnetizationis by applying an external magnetic field. 1 0 1 1 0 1 0 1

  8. Final state How Fast a Magnet can beSwitched…? Today, the time it takes to switch a magnet in is ~ 700ps The speed of this process is proportionalwith the strength of the applied magnetic field. The switching speed may be as high as desiredprovided sufficiently high fields are available!? ~ 700ps Is there any speed limit? Initial state

  9. The Ultimate Speed Limit: a few Picoseconds In 2004… 3 km long Stanford Linear Accelerator in California The shortest and strongest magnetic field on the Earth Magnetic field pulses: 2.3 picoseconds, 3 Tesla “No matter how short and strong the magnetic-field pulse, magnetic recording cannot be made ever faster than picoseconds.”

  10. New Challenge in Magnetic Data Storage Find novel ways to reverse magnetization faster than picoseconds

  11. The dream What if light could reverse Magnetization? Use Light Pulse: One of the shortest man-made event No Magnetic Field! Opto-Magnetic Recording Light could not only transfer but store the information too Unimaginable storage speeds: 100THz and more

  12. Opto-magnetism ? s(-) dM s(+) dM Inverse Faraday effect Magneto-Optics Opto-Magnetism Magnetization changes the polarization of light Controlling magnetization by light Magneto-optics qF ~Mz E E Mz Faraday effect Spins Photons

  13. Is all-optical magnetization reversal feasible? “The amount of the photons involved in the experiments is far not enough to contribute a significant angular momentum.” “In metals, electron-electron scattering appears to make coherent manipulation of magnetization difficult if not impossible.” “… one cannot expect to induce coherent electron spin dynamics in metals with laser pulses of 30 fs duration.” J. Stohr, H. C. Siegmann Magnetism: From Fundamentals to Nanoscale Dynamics, Springer 2006

  14. Ultrafast opto-magnetic recording…? Speed limit? Not enough photons? Electron-electron scattering a problem? Literature says: Ultrafast opto-magnetic recording is IMPOSSIBLE!

  15. …we never say NEVER…

  16. Magneto-Optical image GdFeCo thin film Experimental set-up Amplified Ti:Sapphirelaser, 1 KHz, 40 fs and 800 nm Linear polarized laser pulses Quarter wave plate Circularly polarized laser pulses Metallic amorphous alloy GdFeCo typically used in data storage Magneto-Optical microscope Before laser excitation

  17. Opto-magnetic recording 40 fs pulses at 1kHz Material: GdFeCo, Hext = 0 s+ s- 100mm C.D. Stanciu et al,, Phys. Rev. Lett. 98, 207401 (2007) C.D. Stanciu et al., Phys. Rev. Lett. 99, 047601 (2007)

  18. Each domain is written with a single 40 fs laser pulse Opto-magnetic recording With a single 40 fs laser pulse? Sweeping the pulsed laser beam at high speed across the sample Braking the speed limit of magnetic recording with an effect previously believed impossible!

  19. Ultrafast Opto-Magnetic Recording Traditional Magnetic Recording Switching Magnets with Magnetic Field Switching Magnets with Light Pulses Writing time ~1 ns ~ 100 THz ~ 1 GHz Writing time ~10 fs ~50.000 faster than the actual speed of a Hard Disk Drive

  20. Femtosecond is one quadrillionth of a second, and 40 femtoseconds is all it takes for a bit of data to be written to a magnetic material. Thank you for your attention! & Thank you UMICORE and FWO! Acknowledgements: @ Radboud University Nijmegen, Nijmegen, The Netherlands: Scientific: Dr. F. Hansteen Dr. A. V. Kimel Dr. A. Kirilyuk Prof. Dr. Th. Rasing Technical: Albert van Etteger Tonnie Toonen @ Nihon University, Tokyo, Japan: Dr. A. Tsukamoto Prof. Dr. A. Itoh @ Seagate Research, USA: Dr. Julius Hohlfeld Dr. Adnan Rebei Financial support: ◦The European network DYNAMICS ◦ Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO) ◦NanoNed: Nano-Spintronics ◦Stichting voor Fundamenteel Onderzoek der Materie (FOM) ◦Grant-in-Aid for Scientific Research of the Ministry of Education, Culture, Sports, Science and Technology in Japan ◦ Seagate Research

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