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Magnetic Force Microscopy using Quartz Tuning Fork

Magnetic Force Microscopy using Quartz Tuning Fork. Yongho Seo Center for Near-field Atom-photon technology, Seoul Nation University, Rep. of Korea & Department of Physics, University of Virginia Kyungho Kim, Hyunjun Jang, Wonho Jhe School of Physics and

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Magnetic Force Microscopy using Quartz Tuning Fork

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  1. Magnetic Force Microscopy using Quartz Tuning Fork Yongho Seo Center for Near-field Atom-photon technology, Seoul Nation University, Rep. of Korea & Department of Physics, University of Virginia Kyungho Kim, Hyunjun Jang, Wonho Jhe School of Physics and Center for Near-field Atom-photon technology, Seoul Nation University, Rep. of Korea

  2. Quartz Tuning Fork as a Force Sensor Quartz Crystal Tuning fork Micro-machined Cantilever - optical deflection - laser diode - photo diode - optical alignment - addition actuator - Self actuating - Self sensing - No light - No alignment

  3. Force Sensitivity of Quartz Tuning Fork Cantilever Tuning Fork f ~ 10 - 100 kHz k ~ 1 - 100 N/m Q ~ 102 ~ 10 nm dithering f ~ 32 - 100 kHz k ~ 103 - 105 N/m Q ~ 104 (106 in vacuum) < 1 nm dithering Force sensitivity (Qf/k) 1/2 • Low force sensitivity • Low thermal noise due to high stiffness • High resolution by small dithering amplitude

  4. Previous works : MFM using tuning fork Hal Edwards, et. al. (1997) Todorovic and Schultz (1998)

  5. Tuning Fork based Electrostatic force microscopy • Ferroelectrics • surface charge in Semiconductor f = 32.768 KHz k = 1300 N/m Q = 1300 L = 2.2 mm, t = 190 mm, w = 100 mm

  6. EFM images using Tuning Fork Surface polarization images of PZT film poling Line drawing dot 7 x 7 mm2 0.9 x 0.9 mm2 7 x 7 mm2 4 x 4 mm2 Y. Seo, et al, Appl. Phys. Lett. 80 4324, (2002).

  7. Tuning Fork Based Magnetic Force Microscopy MFM contrast - magnetic force gradient between tip and sample Force gradient Frequency shift Phase shift Magnetic force - very weak force (~pN) Lift mode - keep constant gap between tip and sample (~10 nm) - to avoid the strong short range topographic contrast

  8. Approach Curve of MFM Approach Withdraw Shear force Attractive force f = 0.1 Hz 0.01 Hz 1 mHz high S/N ratio high frequency Sensitivity < 3 mHz

  9. Tip Manufacture Electrochemical Etching - Co or Ni wire H3PO4 H3PO4 Pt Co, Ni D = 100 mm 10 mm

  10. Tip Attachment -Attach the wire to the tuning fork and make a tip -Use home-made micromanipulator Pt Silver paint Co, Ni H3PO4 Tuning fork

  11. Tip & Tuning Fork epoxy Co or Ni tip L = 2.2 mm, t = 190 mm, w = 100 mm spring constant, k = 1300 N/m

  12. Shear Mode MFM Advantage of the shear mode MFM • Perpendicularly • recorded sample • longitudinally • polarized tip • - monopole approximation

  13. Magnetic Force Microscopy Images (a) shear mode, Co tip, perpendicular (b) shear mode, Co tip, parallel dithering (c) shear mode, Ni tip (d) tapping mode 100 Mbit / Inch2 hard disk 30 x 30 mm2 30 x 30 mm2 30 x 30 mm2 30 x 30 mm2

  14. Lift Height & Dithering Amplitude Height (h) dependency Amplitude (a) dependency Tip h a Sample 3 x 1 mm2 13 x 3 mm2

  15. High Resolution Tuning Fork Based MFM 1 Gbit/inch2 hard disk Dithering Amplitude : 20 nm lift height : 50 nm Spatial resolution : 50 nm 2 x 2 mm2

  16. Summary • MFM using Tuning Fork • High resolution. • low power dissipation at low temperature. • No laser : dark environment. • Cryogenic experiment (Vortex in superconductor).

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