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High Sensitivity Magnetic Field Sensor Technology

High Sensitivity Magnetic Field Sensor Technology. David P. Pappas National Institute of Standards & Technology Boulder, CO. Market analysis - magnetic sensors. 2005 Revenue Worldwide - $947M Growth rate 9.4%. Application. Type.

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High Sensitivity Magnetic Field Sensor Technology

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  1. High Sensitivity Magnetic Field Sensor Technology David P. Pappas National Institute of Standards & Technology Boulder, CO

  2. Market analysis - magnetic sensors • 2005 Revenue Worldwide - $947M • Growth rate 9.4% Application Type “World Magnetic Sensor Components and Modules/Sub-systems Markets” Frost & Sullivan, (2005)

  3. Outline • High sensitivity applications • Noise & signal measurement • Description of various types of sensors • Addition of flux concentrators • Summary

  4. Magneto-encephalography Bio-magnetic tag detection Magneto- Cardiography Magnetic RAM Mars Global Explorer (1998) North Caroline Department of Cultural Resources “Queen Anne’s Revenge” shipwreck site Beufort, NC Applications • Health Care • Geophysical • Astronomical • Archeology • Non-destructive evaluation (NDE) • Data storage

  5. B-Field Ranges & Frequencies Industrial 1 nT 1 nT Geophysical Geophysical Industrial/NDE Magneto- cardiography Magneto- cardiography Magnetic field Range 1 pT 1 pT B-field Range Magnetic Anomaly Magnetic Anomaly Magneto- encephalography Magneto- encephalography 1 fT 1 fT 1 1 100 100 10,000 10,000 0.0001 0.0001 0.01 0.01 Frequency (Hz) Frequency (Hz) F.L. Fagaly Magnetics Business & Technology Summer 2002 Adapted from “Magnetic Sensors and Magnetometers”, P. Ripka, Artech, (2001)

  6. Magnetic field strength: H-field in A/m What is actually measured? Magnetic induction field, B (flux density) What are we measuring?Systèm International d’Unitès r (m) I (A) B = m0 H B-field in tesla (T)

  7. B-fields… • Induce currents in conductors • Affect scattering of electrons in matter • Change phase of currents flowing in superconductors • Create energy level splittings in atoms => Use these effects to build a toolbox for field detection in important applications

  8. Magnetometer technologies • Induction • Search Coil • Fluxgate • Scattering • Magneto-resistive, Impedance, Optical, Electric… • Spintronic – Giant MR, Tunnelling MR • Hall Effect • Superconducting • SQUIDS • Spin Resonance • Proton, electron

  9. Bext  Bf State measurement • Low noise excitation source - • Voltage, current, light, … • Sense state with detector • Flux feedback is typical • Linearize • Dynamic Range • Complicated • Limits slew rate & bandwidth S B

  10. 100,000 10,000 1,000 100 10 1 Noise metrology • Magnetically shielded container • Low noise preamplifiers • Spectrum analyzer – P = V2/Hz • power / sensitivity = field noise SQUID Magnetometer State Measurement f T/Hz 0.01 0.1 1 10 100 Hz

  11. ~20 pT 1pT/Hz 1 10 100 1000 .01 0.1 1 10 100 Real time magneto-cardiography High TC SQUID – 1pT/Hz @ 1 Hz Low TC SQUID – 10 fT/Hz @ 1 Hz Oh, et. al JKPS (2007) 1 pT/Hz

  12. Benchmark properties:

  13. Superconducting Quantum Interference Devices I Signal B IR IL B Tunnel Junctions Left-Right phase shifted by B

  14. Pickup loops for SQUIDS • One loop – measure BZ • Two opposing • dBZ/dz (1st order gradiometer) • Good noise rejection • Three – alternating • dBZ2/dz2 (2nd order gradiometer) • High noise rejection N S

  15. SQUID Magnetometer “The SQUID Handbook,” Clarke & Braginski, Wiley-VCH 2004 Commercial: 10 – 100’s k$

  16. Resonance magnetometers • Nuclear spin resonance • Protons • water, methanol, kerosene • Overhauser effect: • He3, Tempone • Electron spin resonance • He4,Alkali metals (Na, K, Rb) Bext

  17. Proton magnetometer • Kerosene cell • Toroidal excitation • & pickup Olsen, et. al (1976) From Ripka, (2001) Commercial: 5 k$

  18. B Electron spin magnetometers Photodetector • Standard cell • Chip scale atomic magnetometer (CSAM) • Rb metal vapor • Spin-exchange relaxation free (SERF) • K metal vapor Vapor cell RF Coils l/4 Filter Laser Budker, Romalis, Nature Physics, 3(4), 227-234 (2007)

  19. e--spin magnetometer - He4 Smith, et al (1991) from Ripka (2001) JPL - SAC-C mission Nov. (2000)

  20. e--spin magnetometer Chip scale atomic magnetometer • Rb metal vapor • Optimized for low power • Very small form factor 4.5 mm P. D. D. Schwindt, et al. APL 90, 081102 (2007).

  21. e--spin magnetometer Spin-exchange relaxation free • K metal vapor • Low field, high density gas • Line narrowing effect • =>Optimized for high sensitivity • All –optical pump/probe Kominis, et. al, Nature 422, 596 (2003)

  22. Ferromagnetic magnetometers • Fluxgate • Magneto-resistive • AMR – Anisotropic MR • GMR – Giant MR • TMR – Tunneling MR • Giant Magneto-impedance • Magneto-striction

  23. Bext Fluxgate Drive(f) Pickup(2f) M M H Bext Hmod(f) “Magnetic Sensors and Magnetometers” P. Ripka, Artech, 2001 Commercial: ~1 k$

  24. Innovations in Fluxgate technology Micro-fluxgates Circumferential Magnetization • Planar fabrication • 80 pT/Hz @ 1 Hz • Apply current in core • Single domain rotation • 100 fT/Hz @ 1 Hz I M Kawahito S., IEEE J. Solid State Circuits 34(12), 1843 (1999) Koch, Rosen, APL 78(13) 1897 (2001)

  25. * * * * Magneto-resistive (MR) sensors I FM • AMR - Anisotropic MR • Single ferromagnetic film • 2% change in resistance • GMR – Cu spacer • Up to 60% change • TMR – Insulator spacer • Insulator => 400% change M FM NM FM “Thin Film Magneto-resistive Sensors S. Tumanski, IOP (2001).

  26. MR sensors - high spatial resolutionHigh Frequency • Data storage • HDD read head 100 Gb/in2 • 1 GHz BW • < 100 pT/Hz from SNR MgO MTJ 100 pT/Hz ~150 nm Frietas, Ferreira, Cardoso, Cardoso J. Phys.: Condens Mater 19 165221 (2007)

  27. I+ I- I- V+ V- 16 mm Ferrofluid image MR Sensors – scalability & imaging • 256 element AMR linear array • Thermally balanced bridges • Image magnetic tapes real time – forensics, archival • NDE imaging Cassette Tape – forensic analysis

  28. MR biomolecular recognition • Nano-scale magnetic labels that attach to target DNA • GMR arrays with probe DNA • Labels are sensed when probes attach to targets => Goal: high sensitivity chemical assays “BARC” Bead Array Counter Device Applications Using Spin Dependent Tunneling and Nanostructured Materials M. Tondra, D. Wang, Z. Qian, Springer Lecture Notes in Physics, V593, 278-289 (2002)

  29. Flux concentrators MR as low field sensors AMR Honeywell Philips 2 Unshielded sensors GMR NVE 2 shielded TMR “Low frequency picotesla field detection…” Chavez, et. al, APL 91, 102504 (2007). Commercial: ~ $

  30. 2 cm The joy of flux concentrators Bext a • Need: • Soft ferromagnet • High M = cH • No hysterisis • Gain up to ~50 • Will it help other sensors?

  31. Spectral noise measurements Si Hall Sensors AMR Fluxgates

  32. +external x10 Internal F.C. x10 Hall, no F.C. Integrated Hall sensors with flux concentrators X 100 improvement with flux concentrators 10-9 10-6 10-3 Magnetic field Popovic, et. al, PROC. 23rd MIEL,, VOL 1, NIŠ, YUGOSLAVIA, 12-15 MAY, 2002

  33. Hall Effect specifications V I InAs thin film Applications Keyboard switches Brushless DC motors Tachometers Flowmeters    Commercial: ~0.1 (sensors) - 1 (integrated) $

  34. Disruptive technologies?Superconducting flux concentrator Hybrid S.C./GMR Field Gain YBCO ~ 100 Nb ~ 500 “…An Alternative to SQUIDs” Pannetier, et. al, IEEE Trans SuperCond 15(2), 892 (2005)

  35. Magneto-electric Magnetostrictive + piezo-electric multilayer H PMN-PT VME Terfenol-D Disruptive No power required Two terminal device High impedance output Dong, Zhai, Xin, Li, Viehland APL V86, 102901 (2005)

  36. Iac Magnetic amorphous wire M Enhanced skin effect in magnetic wire frequency  external field  H Giant Magneto-impedance (GMI) CoFeSiB “Giant magneto-impedance and its applications” Tannous C., Gieraltowski, Jour Mat. Sci: Mater. in Electronics, V15(3) pp 125-133 (2004)

  37. GMI specifications Commercial: ~100 $

  38. Other disruptive technologies • Magneto-strictive delay lines • Magneto-optic sensors • Other spintronic devices

  39. Conclusions • High sensitivity magnetometers research very active • Many advances to be made in conventional devices • Potentially disruptive technologies pursued • Move to smaller, lower power, nano-fabrication

  40. Acknowledgements • Steve Russek • Bill Egelhoff • John Unguris • Mike Donahue • John Kitching • Fabio da Silva • Sean Halloran • Lu Yuan

  41. Spin Transistors

  42. Magneto-optic

  43. Search Coils

  44. x-y-z Hall sensors with internal flux concentrators Schott, et al, IEEE p 978 (2004)

  45. Bound Current Bint~10Bext Bext Bg~Bint M Bext The joy of flux guides: For small gap: Bg ~ 10 Bext “soft” ferromagnet

  46. SQUID devices Nb AlOX ~ 1.5 nm Al • Microfabrication • Nb/Al-AlO/Nb Nb JJ’s Superconducting shielded can

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