O. Fruchart SPINTEC, Univ. Grenoble Alpes / CNRS / CEA-INAC, France - PowerPoint PPT Presentation

O. Fruchart SPINTEC, Univ. Grenoble Alpes / CNRS / CEA-INAC, France www.spintec.fr email: olivier.fruchart@cea.fr Slides: http://fruchart.eu/slides The European School on Magnetism 2017

ESM2017: 10 th Oct Olivier FRUCHART Characterization techniques for nano-sized systems Cargèse, France

What is measured? Environmental conditions Magnetization, induction, Temperature stray field? Field: magnetic field, electric Elemental resolution Electric current, light etc. Direct or indirect? Strain Quantitative or not? Additional measuring techniques Versatility Which specifications? Magnetization: 1D, 2D, 3D Sample preparation needed Depth resolution: surface or volume? Time per one measurement Lateral resolution In situ / ex situ Sensitivity Large-scale or in-lab? Time/Spectral resolution Expensive or cheap? ESM2017: 10 th Oct Olivier FRUCHART Characterization techniques for nano-sized systems Cargèse, France

Magnetic domains Magnetic length scales Numerous and complex shape of domains Magnetic energy 2 𝐹 = 𝐵 𝜖𝑛 𝑗 + 𝐿 sin 2 𝜄 𝜖𝑦 𝑘 Exchange Anisotropy J/m 3 J/m Anisotropy exchange length Δu = 𝐵/𝐿 1 nm → 100 nm History: Weiss domains Hard Soft ESM2017: 10 th Oct Olivier FRUCHART Characterization techniques for nano-sized systems Cargèse, France

Magnetic bits on hard disk drive Underlying microstructure 10 nm magnetic grain Co-based hard disk media : bits 50nm and below S. Takenoiri, J. Magn. Magn. Mater. 321, 562 (2009) B. C. Stipe, Nature Photon. 4, 484 (2010) ESM2017: 10 th Oct Olivier FRUCHART Characterization techniques for nano-sized systems Cargèse, France

Precessional magnetization dynamics Pioneering experiment of precessional magnetization reversal See lecture Christian Back d𝐧 d𝑢 = 𝛿 0 𝐧 × 𝐈 + 𝛽𝐧 × d𝐧 d𝑢 𝛿 0 = 𝜈 0 𝛿 < 𝟏 Gyromagnetic ratio 𝛿 𝑡 = 28 GHz/T 𝛽 > 0 Damping C. Back et al., Science 285, 864 (1999) coefficient >1 μs : th ther ermall lly-activated magnetization proces esses 1 ns ns : precession of of magnetizati tion 1 ps ps : ultr ltrafast dem emagn gneti tization ESM2017: 10 th Oct Olivier FRUCHART Characterization techniques for nano-sized systems Cargèse, France

Spatial resolution Physical phenomenon Global (magnetometry) Probing magnetic field / induction Local (example: small sensors) Light-matter interaction Microscopy Electron-matter interaction Scanning probe Full field Criteria for measurement techniques Probing magnetic stray fields Techniques with light-matter interaction Techniques with electron-matter interaction ESM2017: 10 th Oct Olivier FRUCHART Characterization techniques for nano-sized systems Cargèse, France

1982 : inventing the scanning tunneling microscope G. Binnig, H. Rohrer, C. Gerber & E. Weibel Tunneling through a controllable vacuum gap apl 40, 178 (1982) ESM2017: 10 th Oct Olivier FRUCHART Characterization techniques for nano-sized systems Cargèse, France

1982 : inventing the scanning tunneling microscope G. Binnig, H. Rohrer, C. Gerber & E. Weibel Tunneling through a controllable vacuum gap apl 40, 178 (1982) ESM2017: 10 th Oct Olivier FRUCHART Characterization techniques for nano-sized systems Cargèse, France

https://www.nobelprize.org ESM2017: 10 th Oct Olivier FRUCHART Characterization techniques for nano-sized systems Cargèse, France

Probing The Atomic Force Microscope (AFM) Mechanical force -> Topography, tribology ( adhesion etc.) Electric forces -> ferroelectric domains, semiconductor memory cells etc. Magnetic force -> magnetic domains Detection Laser deflection / interference Capacitance G. Binnig et al., Phys. Rev. Lett. 56, 930 (1986) ESM2017: 10 th Oct Olivier FRUCHART Characterization techniques for nano-sized systems Cargèse, France

Work under forced ac excitation Amplitude The cantilever as an oscillator 𝑅 = 10/ 2 with: Mere renormalization: 𝑅 = 1/ 2 𝜕/𝜕 0 Probing forces with the phase shift Phase Attractive: red shift ift 𝑅 = 10/ 2 Rep epuls lsiv ive: blu lue shift ift 𝑅 = 1/ 2 𝜕/𝜕 0 𝜕/𝜕 0 ESM2017: 10 th Oct Olivier FRUCHART Characterization techniques for nano-sized systems Cargèse, France

Example Operation: two-pass technique First pass: measure topography Second pass: measure magnetism NB: other measurement modes exist 2x2 µm, Pd\Co\Au multilayer, 80mT (co-existence of stripes and bubbles) Y. Zhu Ed., Modern techniques for charact- erizing magnetic materials, Springer (2005) http://olivier.fruchart.eu/slides Sample courtesy: C. Bouard, P. Warin ESM2017: 10 th Oct Olivier FRUCHART Characterization techniques for nano-sized systems Cargèse, France

What is measured? Environmental conditions Stray field? Temperature Indirect? Field: magnetic field, electric Hardly quantitative Electric current, light etc. Strain Additional measuring techniques Versatility Which specifications? Depth resolution: surface/volume No sample preparation needed Lateral resolution: 25-50nm Time per measurement: few mn Sensitivity: medium (1nm thickness) Ex situ Time/Spectral resolution: slow In-lab, cheap May influence sample ESM2017: 10 th Oct Olivier FRUCHART Characterization techniques for nano-sized systems Cargèse, France

Based on: transmission electron microscopy Example The Fresnel mode Y. Zhu Ed., Modern techniques for charact- erizing magnetic materials, Springer (2005) Skyrmion lattice in Fe 0.5 Co 0.5 Si Hig Highlig ights gr gradients of of magn gneti tization: X. Z. Yu et al., Nature 465, 901 (2010) dom omain in walls lls, vor ortices etc. c. Probes in induction: magnetization + str tray field field 2D maps may be be rec econstructed < 5nm nm spatia tial resolu lution ESM2017: 10 th Oct Olivier FRUCHART Characterization techniques for nano-sized systems Cargèse, France

The Foucault mode High Highlig ights magnetic ic dom omain ins 2D 2D map aps of of in induction may be e rec econstru ructed ed <5nm sp <5n spatia tial res esolution Imaging courtesy: A. Masseboeuf ESM2017: 10 th Oct Olivier FRUCHART Characterization techniques for nano-sized systems Cargèse, France

Based on: transmission electron microscopy Principle Highli ligh ghts is isolin ines of of z component of of vector pot oten enti tial 2D maps of of induction may be be reconstructed <1 <1-2nm sp spatia tial l res esolu lution H. S. Park et al., Nat. Nanotech 9, 337 (2014) ESM2017: 10 th Oct Olivier FRUCHART Characterization techniques for nano-sized systems Cargèse, France

Principle Gather 2D set of images at different ( θ , ψ ) tilts Reconstruct 3D magnetization pattern with iteration algorithm Note: no bijection, unlike the structural case T. Tanigaki et al., Nanolett 15, 1309 (2015) 3D maps of of induction may be be rec econstructed ed <2 <2nm spatia tial res esolution Cu Cutting edge Still debated… ESM2017: 10 th Oct Olivier FRUCHART Characterization techniques for nano-sized systems Cargèse, France

What is measured? Environmental conditions Induction Temperature No elemental resolution Field: magnetic field, electric Direct Electric current, light etc. Quantitative Strain Additional measuring techniques Versatility Which specifications? Magnetization: 1D-3D Sample preparation needed Depth resolution: integrated, <100nm Time per measurement: seconds Lateral resolution: <5nm In situ / ex situ Sensitivity: >1nm Large-scale or in-lab? Time resolution: cutting-edge Expensive or cheap? ESM2017: 10 th Oct Olivier FRUCHART Characterization techniques for nano-sized systems Cargèse, France

Example Measurement of of str tray fie field ld High sensiti tivity (local (l magnetometer) May be be turned ed in into scannin ing probe Versatil ile for measurement, not ot for or fabrication Med ediu ium dynamics Patterned magnetic dot on a Hall cross M. Rahm et al., Appl. Phys. Lett. 82, 4110 (2003) ESM2017: 10 th Oct Olivier FRUCHART Characterization techniques for nano-sized systems Cargèse, France

Principle Example Resonant excitation J.-P. Tetienne et al., JAP 115, 17D501 (2014) of an NV center in diamond with triplet state: sensitive to Zeeman splitting Mounted on AFM tip + scanning + confocal microscope Pt\Co(6Å)\AlOx stack L. Rondin et al., Nat. Comm 4, 2279 (2013) Difference between Néel & Bloch walls Extreme se sensit sitiv ivity (µT (µT) Probes Dzyaloshinskii- Needs mod odeli ling (s (str tray fie field ld + quanti tization axis xis) Moriya physics ESM2017: 10 th Oct Olivier FRUCHART Characterization techniques for nano-sized systems Cargèse, France

Criteria for measurement techniques Probing magnetic stray fields Techniques with light-matter interaction Techniques with electron-matter interaction ESM2017: 10 th Oct Olivier FRUCHART Characterization techniques for nano-sized systems Cargèse, France