phd thesis, claudiu daniel stanciu

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

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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). - PowerPoint PPT Presentation

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Page 1: PhD thesis,  Claudiu Daniel Stanciu

Radboud University Nijmegen

PhD thesis, PhD thesis, Claudiu Daniel StanciuClaudiu Daniel Stanciu

Radboud University Nijmegen, The Netherlands (2004 - 2008)Radboud University Nijmegen, The Netherlands (2004 - 2008)(now working at Océ Technologies)(now working at Océ Technologies)

Page 2: PhD thesis,  Claudiu Daniel Stanciu

Radboud University Nijmegen

Over 110 years Over 110 years of Magnetic Recordingof Magnetic Recording

Telegraphone (by Valdemar Poulsen)

The first working magnetic recorder (1898)

The first hard disk drive – HDD (1955)

5MB memory storage (IBM)

The first magnetic tape (1928)

Magnetophon (Fritz Pfleumer)

The first magnetic core memory (late 1940’s)

IBM

Page 3: PhD thesis,  Claudiu Daniel Stanciu

Radboud University Nijmegen

Magnetic Recording Devices Magnetic Recording Devices TodayToday

The first hard disk drive – HDD (1955)

5MB memory storage (IBM)

Hard disk drive – HDD (2010)

5GB memory storage

Page 4: PhD thesis,  Claudiu Daniel Stanciu

Radboud University Nijmegen

MagneticMagnetic DataData Storage Storage

Hard Disk Drive(HDD) 0 1 1 0

Magnetic Bits

Magnetic domains in a HDD

- black areas- black areas - white areas- white areas

Page 5: PhD thesis,  Claudiu Daniel Stanciu

Radboud University Nijmegen

ChallengesChallenges in Magnetic Data Storage in Magnetic Data StorageHigher and higher bit density Higher and higher data storage speed

FASTER switching speedof the tiny magnets

SMALLER magnetic areas(tinier magnets)

This thesis focuses on the speed of the magnetization switchingThis thesis focuses on the speed of the magnetization switching

“By 2012, just two disks will provide the same storage capacity as the human brain!”

Robert Birge (Syracuse University)

~ 10 Terabyte ~ 10 Terabyte

FAST!FAST!

Page 6: PhD thesis,  Claudiu Daniel Stanciu

Radboud University Nijmegen

??

How to How to SwitchSwitch a Magnet…? a Magnet…?

Page 7: PhD thesis,  Claudiu Daniel Stanciu

Radboud University Nijmegen

ConventionalConventional Magnetic Data Magnetic Data StorageStorage

11 00 11 00 0011 11 11

The conventional way The conventional way of reversing magnetizationof reversing magnetization

is by applying an external magnetic field.is by applying an external magnetic field.

Page 8: PhD thesis,  Claudiu Daniel Stanciu

Radboud University Nijmegen

Initial Initial statestate

Final Final statestate

How FastHow Fast a Magnet a Magnet can becan be SwitchedSwitched……??

Today, the time it takes to switch a magnet in is ~ 700ps

The The speedspeed of this process is of this process is proportionalproportional withwith the strength of the strength of the applied magnetic fieldthe applied magnetic field..

The switching speed The switching speed may be as high as desiredmay be as high as desired

provided sufficiently high fields are available!?provided sufficiently high fields are available!?~ 700ps

Is there any speed limit?Is there any speed limit?

Page 9: PhD thesis,  Claudiu Daniel Stanciu

Radboud University Nijmegen

““No matter how short and strong the magnetic-field pulse, No matter how short and strong the magnetic-field pulse, magnetic recording cannot be made ever faster than picoseconds.”magnetic recording cannot be made ever faster than picoseconds.”

The Ultimate Speed Limit: The Ultimate Speed Limit: a few Picosecondsa few Picoseconds

Magnetic field pulses: 2.3 picoseconds, 3 Tesla

3 km long Stanford Linear Accelerator in California

The shortest and strongest magnetic field on the Earth

In 2004…In 2004…

Page 10: PhD thesis,  Claudiu Daniel Stanciu

Radboud University Nijmegen

New ChallengeNew Challenge in Magnetic Data Storage in Magnetic Data Storage

Find novel waysFind novel ways to reverse magnetization to reverse magnetization

faster than picosecondsfaster than picoseconds

Page 11: PhD thesis,  Claudiu Daniel Stanciu

Radboud University Nijmegen

The dreamThe dream

What if light could reverse What if light could reverse Magnetization?Magnetization?

Opto-MagneticOpto-MagneticRecordingRecording

Use Light Use Light PulsePulse: One of : One of the the shortest shortest man-made man-made

eventevent

Unimaginable Unimaginable storage storage speeds:speeds:

100THz and 100THz and moremore

Light could not only Light could not only transfer but store transfer but store the information toothe information too

Page 12: PhD thesis,  Claudiu Daniel Stanciu

Radboud University Nijmegen

Magnetization changes the polarization of lightMagnetization changes the polarization of light

SpinsSpins PhotonsPhotons

Controlling magnetization by lightControlling magnetization by light

Magneto-OpticsMagneto-OpticsOpto-MagnetismOpto-Magnetism

??Opto-magnetismOpto-magnetism

MM

MM

(-)(-)

(+)(+)

Inverse Faraday effectInverse Faraday effect

Magneto-opticsMagneto-optics

EE

EE

F F ~M~Mzz

MMzz

Faraday effectFaraday effect

Page 13: PhD thesis,  Claudiu Daniel Stanciu

Radboud University Nijmegen

Is all-optical magnetization reversal feasible?Is all-optical magnetization reversal feasible?

““The amount of the photons involved in the experiments The amount of the photons involved in the experiments is far not enough to contribute a significant angular momentum.”is far not enough to contribute a significant angular momentum.”

““In metals, electron-electron scattering appears to make coherent In metals, electron-electron scattering appears to make coherent manipulation of magnetization difficult if not impossible.”manipulation of magnetization difficult if not impossible.”

J. Stohr, H. C. Siegmann J. Stohr, H. C. Siegmann Magnetism: From Fundamentals to Nanoscale Dynamics,Magnetism: From Fundamentals to Nanoscale Dynamics, Springer 2006 Springer 2006

“… “… one cannot expect to induce coherent electron spin one cannot expect to induce coherent electron spin dynamics in metals with laser pulses of 30 fs duration.”dynamics in metals with laser pulses of 30 fs duration.”

Page 14: PhD thesis,  Claudiu Daniel Stanciu

Radboud University Nijmegen

Ultrafast opto-magnetic recording…?Ultrafast opto-magnetic recording…?

Speed limit?Speed limit?

Not enough photons?Not enough photons?

Electron-electron scattering a problem?Electron-electron scattering a problem?

Literature says:Literature says:Ultrafast opto-magnetic recording is IMPOSSIBLE!Ultrafast opto-magnetic recording is IMPOSSIBLE!

Page 15: PhD thesis,  Claudiu Daniel Stanciu

Radboud University Nijmegen

……we never say we never say NEVERNEVER……

Page 16: PhD thesis,  Claudiu Daniel Stanciu

Radboud University Nijmegen

Experimental set-upExperimental set-up

Metallic amorphous alloyMetallic amorphous alloyGdFeCoGdFeCo

typically used intypically used indata storagedata storage

Circularly polarizedCircularly polarizedlaser pulseslaser pulses

Quarter waveQuarter waveplateplate

Linear polarizedLinear polarizedlaser pulseslaser pulses

Magneto-OpticalMagneto-Opticalmicroscopemicroscope

Amplified Ti:Sapphire Amplified Ti:Sapphire laserlaser, 1 KHz, , 1 KHz, 40 fs40 fs and 800 nm and 800 nm

Before laserBefore laserexcitationexcitation

GdFeCo thin filmGdFeCo thin film

Magneto-Optical imageMagneto-Optical image

Page 17: PhD thesis,  Claudiu Daniel Stanciu

Radboud University Nijmegen

Opto-magnetic recordingOpto-magnetic recording

100100mm

HHextext = 0 = 0Material: GdFeCo,Material: GdFeCo,40 fs pulses at 1kHz40 fs pulses at 1kHz

C.D. Stanciu et al,, C.D. Stanciu et al,, Phys. Rev. Lett. 98, 207401 (2007) Phys. Rev. Lett. 98, 207401 (2007) C.D. Stanciu et al., C.D. Stanciu et al., Phys. Rev. Lett. 99, 047601 (2007)Phys. Rev. Lett. 99, 047601 (2007)

Page 18: PhD thesis,  Claudiu Daniel Stanciu

Radboud University Nijmegen

Sweeping the pulsed laser beam at high speed across the sampleSweeping the pulsed laser beam at high speed across the sample

Each domain is written with a Each domain is written with a singlesingle 40 fs laser pulse 40 fs laser pulse

Braking the speed limit of magnetic recording with an Braking the speed limit of magnetic recording with an effect previously believed impossible!effect previously believed impossible!

With a single 40 fs laser pulse?With a single 40 fs laser pulse?

Opto-magnetic recordingOpto-magnetic recording

Page 19: PhD thesis,  Claudiu Daniel Stanciu

Radboud University Nijmegen

Writing time ~ 1 ns

Switching Magnets with Magnetic FieldSwitching Magnets with Magnetic Field

~ 1 GHz

Switching Magnets with Light PulsesSwitching Magnets with Light Pulses

Writing time ~10 fs ~ 100 THz

Traditional Magnetic RecordingTraditional Magnetic RecordingUltrafast Opto-Magnetic RecordingUltrafast Opto-Magnetic Recording

~50.000 faster than the actual speed of a Hard Disk Drive

Page 20: PhD thesis,  Claudiu Daniel Stanciu

Radboud University Nijmegen

Femtosecond Femtosecond is one quadrillionth of a second, is one quadrillionth of a second, and 40 femtoseconds and 40 femtoseconds

is all it takes for a bit of data to be written is all it takes for a bit of data to be written to a magnetic materialto a magnetic material.

Thank you for your attention!

&

Thank you UMICORE and FWO!