Olivier FRUCHART Univ. Grenoble Alpes / CEA / CNRS, SPINTEC, France - - PowerPoint PPT Presentation

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Olivier FRUCHART Univ. Grenoble Alpes / CEA / CNRS, SPINTEC, France - - PowerPoint PPT Presentation

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Olivier FRUCHART Univ. Grenoble Alpes / CEA / CNRS, SPINTEC, France Olivier FRUCHART SPM for magnetism ESM2019, Brno, Czech Republic Quizz #0 Dipolar energy is positive Dipolar energy results Dipole-dipole energy may from dipole-dipole

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Olivier FRUCHART

  • Univ. Grenoble Alpes / CEA / CNRS, SPINTEC, France
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Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

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Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

Quizz #0

ℰd = 1 2 𝜈0 ම

𝒲

𝐈d

𝟑 d𝒲

Dipolar energy is positive Dipolar energy results from dipole-dipole energy Dipole-dipole energy may be negative ℰ = −2 𝜈0𝜈1𝜈2 4𝜌𝑠3

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Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

Quizz #1

ℰ = −2 𝜈0𝜈1𝜈2 4𝜌𝑠3 ℰ = + 𝜈0𝜈1𝜈2 4𝜌𝑠3

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Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

Quizz #2

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Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

Numerous and complex shape of domains

Magnetic domains

History: Weiss domains

Magnetic length scales

Exchange

𝐹 = 𝐵 𝜖𝑛𝑗 𝜖𝑦𝑘

2

+ 𝐿 sin2 𝜄

Anisotropy

J/m J/m3 Anisotropy exchange length Δu = 𝐵/𝐿 1 nm → 100 nm

Hard Soft

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Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

Samples made with lithography or ex situ OK ? Need for sample preparation ? Compatible with various environments ? (temperature, field etc.)

Versatility Access

Large-scale instrument or in-lab ? Expensive or cheap ?

Imaging speed

Sample preparation needed ? How much time for one image ?

What is probed

Surface or volume technique ? Sensitivity ? Magnetization, stray field, other ?

No No univ iversal tech echnique Many cri criteria to to be be bala lanced

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Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

  • G. Binnig, H. Rohrer, C. Gerber & E. Weibel Tunneling through a

controllable vacuum gap Appl. Phys. Lett. 40, 178 (1982)

1982 : inventing the scanning tunneling microscope

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Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

  • G. Binnig, H. Rohrer, C. Gerber & E. Weibel Tunneling through a

controllable vacuum gap Appl. Phys. Lett. 40, 178 (1982)

1982 : inventing the scanning tunneling microscope

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Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

https://www.nobelprize.org

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Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

Topography – Large scale High resolution and sensitivity

Self-organized growth of magnetic dots (Co)

  • O. Fruchart et al., Phys. Rev. Lett. 23 (14), 2769 (1999)

350 x 350 nm

100 x 100 nm

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Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

Spectroscopy → Elemental information High resolution and sensitivity

Dots embedded in Au matrix

100 x 100 nm

TOPOGRAPHY SPECTROSCOPY

  • 0.8

1 2

  • 0.4

Sample voltage (V) dI/dV (nA/V)

0.4 0.8

Co Au

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SLIDE 13

Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

Mapping surface quantum well states Atom manipulation

For magnetism: H. Oka et al., Spin-polarized quantum confinement in nanostructures: Scanning tunneling microscopy, Rev. Mod. Phys. 86, 1127- 1168 (2014) Fe atoms on Copper, low temperature http://research.physics.berkeley.edu/crommie

  • D. Eigler, Nature (1990)

Xe atoms, low temperature

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Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

Courtesy: W. Wulfhekel

Spectroscopic principle

Same principle as tunneling magnetoresistance (TMR) in the solid state

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Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

  • R. Wiesendanger et al., Rev. Mod. Phys. 81, 1495 (2009)

First hints: apparent height of AF atomic steps on Cr(001)

CrO2 tip

Spectroscopy: the Cr(001) surface

  • M. Kleibert et al., Phys. Rev. Lett. 85, 4606 (2000)
  • R. Wiesendanger et al.,
  • Phys. Rev. Lett. 65, 247 (1990)

100nm Fe-coated W tip

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Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

Modulation technique (deprecated)

  • H. Ding at al., Europhys. Lett. 57, 100 (2002)

Co(0001) – Micro-domain wall ac modulation of magnetization of soft bulk tip Lock-in detection of tunneling current

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Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

Antiferromagnetic Fe/W(001)

  • M. Bode et al., Nat. Mater. 5,

477-481 (2006) One monolayer Fe

Current-assisted switching

  • S. Krause et al., Science 317,

1537 (2007) 1ML Fe(110)/W(110)

Skyrmions, write & delete

  • N. Romming et al., Science

341, 636 (2013)

  • R. Wiesendanger et al., Rev. Mod. Phys. 81, 1495 (2009)
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Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

Principle

  • P. Turban, H. Marie, Rennes

Au[2.2nm]/Fe[1]/Au[ 2.6]/Fe[1.6]/GaAs Sen Sensitive to to transport Hig High contrast Hig High spa spatial reso esolu lution (5-10 10 nm nm?) Not

  • t so

so ver ersatil ile

Assets

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SLIDE 19

Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

Probing Mechanical force -> Topography, tribology ( adhesion etc.) Magnetic force

  • >

magnetic domains Electric forces -> ferroelectric domains, semiconductor memory cells etc. Detecting Laser deflection / interference Capacitance Key elements of an Atomic Force Microscope (AFM)

  • G. Binnig et al., Phys. Rev. Lett. 56, 930-933 (1986)
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Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

Inertia Damping Spring External force Seek solutions for Reference angular velocity Quality factor

Mechanical excitation of cantilevers Notations Amplitude Dephasing

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Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

Attractive force with Red shift Repulsive force Blue shift

Tip-sample interaction treated as perturbation Phase shift

Mere renormalization:

Forces monitored th through phase e shift ift Not

  • tice my con
  • nven

ention : dec ecreasin ing phase 𝑛 ሷ 𝑨 + Γ ሶ 𝑨 + 𝑙𝑨 = 𝐺

𝑨(𝑨)

𝐺

𝑨 𝑨 = 𝐺 𝑨0 + 𝑨 − 𝑨0 𝜖𝑨𝐺 𝑨

𝜀𝜒 = − 𝑅 𝑙 𝜖𝑨𝐺

𝑨

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Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

First report : Review :

  • Y. Martin et al., Appl. Phys. Lett. 50, 1455 (1987)
  • R. Proksch et al., Modern techniques for characterizing

magnetic materials, Springer, p.411 (2005)

Two-pass technique

Fe dot (25nm), 2.5x1 microns

Topography Magnetism

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Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

𝐹1,2 = −𝜈0𝜈2. 𝐼d 𝐹1,2 = −𝜈0 𝜈𝑦. 𝐼d,𝑦 + 𝜈𝑧. 𝐼d,𝑧 + 𝜈𝑨. 𝐼d,𝑨 𝜀𝜒 = 𝑅 𝑙 𝜈0𝜈𝑗𝜖𝑨

2𝐼d,𝑗

𝐹1,2 = 𝜈0𝜏. 𝜚 𝐺

𝑨 = −𝜈0𝜏𝐼d,𝑨

𝜀𝜒 = 𝑅 𝑙 𝜈0𝜏𝜖𝑨𝐼d,𝑨

Tip is a dipole Tip is a monopole In In practice, a com

  • mbin

ination of

  • f both
  • th mod
  • del

els is is bes est suit ited ed (d (dip ipole le is is more im important) t) MFM is is sen ensit itiv ive to to som

  • me deri

erivative( e(s) of

  • f th

the str tray field field fr from th the sample le

Quantitative analysis, see e.g.: H. Hug, J. Appl. Phys. 83, 5609 (1998) and followers

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Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

Ultimate spatial resolution: 20nm ?

1x1 µm

Definition-depen enden ent: FWHM, variance, 85 85% etc. Make statis istic ics: ob

  • bje

ject, ori

  • rientati

tion etc. Advan anced: modelin ing, dec econvoluti tion

FePt, epitaxial (4nm)

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SLIDE 25

Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

Spatial resolution Sensitivity Non-invasive 1x1 µm

Tri ricks lie lie in in tip tips All ll matters: sen ensit itiv ivity, resolution, in invasivity, , coe

  • erciv

ivity…

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Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

Courtesy: O. Klein, Grenoble

Principle: measure ferromagnetic resonance with MFM

Measures the longitudinal (static) moment Magnetic biasing of the sample with the stray field of tip allows some kind of imaging

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Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

  • O. Klein et al., Phys. Rev. B 78, 144410 (2008)

Example: FMR spectra of a permalloy disk with diameter 1000nm

Measurements Simulation of FMR modes

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Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

  • L. Rondin et al., Nat. Comm. 4, 2279 (2013)

Principle: spectroscopy of a Nitrogen-Vacancy center in a diamond nanocrystal

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Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

Square Fe20Ni80 dot Signature of flux-closure

5 𝜈𝑛

  • L. Rondin et al., Nat.
  • Comm. 4, 2279 (2013)

Micromagnetics Sensitivity: image antiferromagnetic domains

Hig High sen sensit itivity Poss

  • ssib

ibly qu quantitative in n fi field Qu Quantitativ ive rec econstruction of

  • f

mag agnetiz izatio ion pa pattern no not t straig ightforw rward Imag Imaging un under hig high mag agnetic fi field no not t pos possib ible

Assets

  • P. Appel et al., Nano Lett. 19, 1682 (2019)

Cr203 200nm thin film

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Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

Courtesy: M. Miron, Grenoble

Near-field optics Implementation for magnetic microscopy

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Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

Courtesy: M. Miron, Grenoble

Out-of-plane magnetization

Rea easonable spa spatial reso esolu lution Co Compatible wit ith tim ime reso esolu lutio ion Ha Hardly ly qu quantitative

Assets

AFM Ultrathin Pt/Co/Pt film P-SNOM

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SLIDE 32

Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

No Sp-STM SEMPA SPLEEM TEM XMCD

  • PEEM

XMCD- microscopy (Fresnel ZP) Resolution In-field Versatile* Dynamics <1nm 10nm 10nm 1-2nm 25nm → 10nm 15nm YES local No? Limited No? YES No Limited UHV Limited Yes Limited Part No No Part Yes Yes Element- sensitive Limited Limited Yes Yes MFM

𝑛𝑗

15nm Limited YES Part

Hd

Limited

m m 𝑛𝑦,𝑧 𝑛k 𝑛k

NV 5-10 nm Limited Yes No

Hd

Sensitivity Sensitivity High Med High Med High Low High High No BEMM 1-5nm Med YES No No No

𝑛𝑗

SNOM 50-100nm? Med YES Limited Yes No

unsure

Limited

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Olivier FRUCHART – SPM for magnetism ESM2019, Brno, Czech Republic

[1] Handbook of magnetism and advanced magnetic materials, H. Kronmüller and S. S. P. Parkin Eds., Wiley (2007). VOLUME 3: Novel Techniques for Characterizing and Preparing Samples [2] Magnetic microscopy of nanostructures, Oepen Ed., Springer (2005) [3] Modern techniques for characterizing magnetic materials, Y. Zhu Ed., Springer (2005) [4] Magnetic domains, A. Hubert, R. Schäfer, Springer (1999, reed. 2001

More extensive slides on: http://magnetism.eu/esm/repository-topics.html#techniques Lecture notes from undergraduate lectures, plus various slides on microscopy (MFM etc.): http://fruchart.eu/olivier/slides/

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www.spintec.fr | email: olivier.fruchart@cea.fr