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High Sensitivity Magnetic Field Sensor Technology overview

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Presentation on theme: "High Sensitivity Magnetic Field Sensor Technology overview"— Presentation transcript:

1 High Sensitivity Magnetic Field Sensor Technology overview
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 Applications Health Care Geophysical Astronomical Archeology
Magnetic RAM Magneto-encephalography Magneto- Cardiography “Biomagnetism using SQUIDs: Status and Perspectives” Sternickel, Braginski, Supercond. Sci. Technol. 19 S160–S171 (2006). Bio-magnetic tag detection Frietas, ferreira, Cardoso, Cardoso J. Phys.: Condens. Mater 19, (2007) North Caroline Department of Cultural Resources “Queen Anne’s Revenge” shipwreck site Beufort, NC Mars Global Explorer (1998) Health Care Geophysical Astronomical Archeology Non-destructive evaluation (NDE) Data storage JPL - SAC-C mission Nov. (2000) SI units

5 SI - Le Système International d’Unitès
“Magnetic field intensity”: H-field  A/m What do we measure? B = flux density = “Magnetic induction” field r (m) I (A) Use m0 = permeability of free space F = BA A B = m0 H B-field  tesla (T) kg/(As2) H = ~0.1 A/m B = 210-7 T e.g. 1 1 m Frequency

6 B-field Ranges & Frequencies
1 mT 1 gauss  10-4 T ~ Earth’s B-field 1 mT 1 1 m Industrial 1 nT Geophysical Geophysical Industrial/NDE Magneto- cardiography 1 nT Magnetic field Range B-field Magnetic Anomaly Magneto-cardiography 1 pT Magnetic Anomaly 1 pT Magneto- encephalography Magneto- encephalography 1 fT 1 fT 0.0001 0.0001 0.01 0.01 1 1 100 100 10,000 10,000 Frequency (Hz) Frequency (Hz) F.L. Fagaly Magnetics Business & Technology Summer 2002 Adapted from “Magnetic Sensors and Magnetometers”, P. Ripka, Artech, (2001) effects

7 B-fields… Induce voltages 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 Technologies

8 Magnetometer technologies
Induction Search Coil Fluxgate Giant magneto-impedance Scattering Anisotropic magneto-resistive (AMR) Spintronic – Giant MR, Tunneling MR, Spin Xtor… Hall Effect Magneto-optical Superconducting SQUIDS Spin Resonance Proton, electron State

9 S S B 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 Bf S Bext S B Noise

10 Noise metrology Magnetically shielded container
(or room) Low noise preamplifiers Spectrum analyzer – P = V2/Hz field noise = power / sensitivity Units: Low TCSQUID magnetometer (w/gradiometer) 1 10 100 1,000 10,000 100,000 1/f White State Measurement f T/Hz Preamp Hz Benchmarks

11 Benchmark properties:
State variable V, f, etc B-field measurement Vector/scalar 1 Hz T/Hz Operating T Cryogenic/RT Volume of sense element cm3 – mm3 Power – form factor Line/Battery SQUID

12 Superconducting Quantum Interference Devices
Signal I Superconductor B B IL IR Tunnel Junctions Left-Right phase shifted by B PU loop

13 Pickup loops for SQUIDS
One loop: measure BZ Two opposing loops: dBZ/dz (1st order gradiometer) Good noise rejection Opposing gradiometers: dBZ2/dz2 (2nd order gradiometer) High noise rejection N S Z SQUID specs

14 SQUID Magnetometer State variable Voltage (10’s mV) B-field
Integrated Systems State variable Voltage (10’s mV) B-field Vector, gradients 1 Hz ~10 fT/Hz Low TC Operating T cryogenic Volume ~ 1 cm3 coil Power Line Discrete components Commercial: 10 – 100’s k$ “The SQUID Handbook,” Clarke & Braginski, Wiley-VCH 2004 Resonance

15 Real time magneto-cardiography with SQUID magnetometer
Oh, et. al JKPS (2007) ~60 pT Benchmark

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

17 Proton magnetometer State variable Frequency ~ kHz B-field Scalar
1 Hz sources ~10 pT/Hz depolarization Operating T -20 => 50 oC Volume 1 cm3 cell Power Battery Kerosene cell Toroidal excitation & pickup Commercial: 5 k$ Olsen, et. al (1976) From Ripka, (2001) e- spin

18 Electron spin magnetometers
Photodetector Vapor cell Bext RF Coils l/4 Filter Laser Budker, Romalis, Nature Physics, 3(4), (2007) He4

19 He4 e--spin magnetometer
State variable Frequency ~ MHz B-field vector/scalar 1 Hz 1 pT/Hz Operating T ambient Volume ~10 cm3 cell Power battery JPL - SAC-C mission Nov. (2000) Smith, et al (1991) from Ripka (2001) CSAM

20 e--spin magnetometer Chip scale atomic magnetometer
State variable Frequency B-field Scalar 1 Hz 5 pT/Hz Operating T 110 oC Volume 20 mm3 Power Small battery Rb metal vapor Optimized for low power Very small form factor 4.5 mm P. D. D. Schwindt, et al. APL 90, (2007). SERF

21 e--spin magnetometer Spin-exchange relaxation free
K metal vapor Low field, high density of atoms Line narrowing effect All-optical excitation & pickup =>Optimized for high sensitivity State variable Frequency B-field Vector < 100 nT 1 Hz < 1 fT/Hz Operating T 180 oC Volume ~ 3 cm3 Power line Kominis, et. al, Nature 422, 596 (2003) Solid state

22 Solid state magnetometers
Inductive Fluxgate Giant magneto-impedance Magneto-resistive AMR – Anisotropic MR Spintronic GMR – Giant MR TMR – Tunneling MR Disruptive technologies Hybrid superconductor/solid state Magneto-striction

23 Fluxgate Commercial: ~1 k$ Bext State variable Inductive 2f B-field
Drive(f) Pickup(2f) Bext State variable Inductive 2f B-field Vector 1 Hz sources <10 pT/Hz Magnetic Johnson Perming Operating T RT Volume 1 cm3 Power battery M M H Bext Hmod(f) Commercial: ~1 k$ “Magnetic Sensors and Magnetometers” P. Ripka, Artech, 2001 FG innov.

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

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

26 GMI specifications Commercial: ~100 $ State variable Z @ MHz B-field
Vector 1 Hz sources ~3 nT/Hz 1/f mag noise Temp fluct. M Johnson Perming Operating T RT Volume 0.01 mm3 wire Power Batter Commercial: ~100 $ MR

27 Magneto-resistive (MR) sensors
AMR - Anisotropic MR Single ferromagnetic film NiFe 2% change in resistance Spintronic: GMR – Metal spacer 60% DR/Rmin Co/Cu/Co Parkin, APL (1991) TMR – Insulator spacer 472% DR/Rmin at R.T. CoFeB/MgO/CoFeB Hayakawa, APL (2006) I “Thin Film Magneto-resistive Sensors S. Tumanski, IOP (2001). M FM * * NM FM * hdd

28 MR Sensors – spatial resolution
V+ V- I- 16 mm x 256 I+ 256 element AMR linear array Thermally balanced bridges High speed magnetic tape imaging – forensics, archival NDE imaging Current flow in VLSI RAM w/short 2 cm -Iy +Ix -Ix +Iy 4 mm Cassette Tape – forensic analysis 4 mm 45 mm erase head stop event write head BARC. da Silva, et al., subm. RSI (2007)

29 MR biomolecular recognition
Nano-scale magnetic labels that attach to target GMR arrays with probe Probes attach to targets  Need very sensitive magnetic detector arrays  Goal: high accuracy chemical assays “BARC” Bead Array Counter Device Applications Using SDT, Tondra et. al Springer Lecture Notes in Physics, V593, (2002) MR sens.

30 MR as low field sensors Commercial: ~ $ State variable Resistance
AMR Large area films State variable Resistance B-field Vector 1 Hz sources ~200 pT/Hz 1/f mag noise Temp fluct. M Johnson/Shot Perming Operating T RT Volume 0.001 mm3 film Power battery 2 Unshielded sensors GMR Small sensors Flux concentrators 2 shielded TMR Commercial: ~ $ “Low frequency picotesla field detection…” Chavez, et. al, APL 91, (2007). F.C.

31 The joy of flux concentrators
Bext a Need: Soft ferromagnet High M = cH No hysterisis Gain up to ~50 No increase in noise Increase in form factor TMR with F.C. 2 cm Noise

32 Spectral noise measurements
without flux concentrator 1 n with external flux concentrator 1 p Stutzke, Russek, Pappas, and Tondra, J. Appl. Phys. 97, 10Q107 (2005) Yuan, Halloran, da Silva, Pappas, J. Appl. Phys. submitted (2007) Hall FC

33 Integrated Hall sensors with flux concentrators
Internal flux concentrators Hall element 1Hz (nT/Hz) White noise (f> 100 Hz) Hall with no flux concentrators* 300 200 Only internal flux concentrators 30 With both internal and external flux concentrators 3 “Bridging the gap between AMR, GMR and Hall Magnetic sensors Popovic, et. al, PROC. 23rd MIEL, V1, NIŠ, YUGOSLAVIA, MAY, 2002 Hall spec.

34 Hall Effect specifications
V State variable Voltage B-field Vector 1 Hz 300 nT/Hz 30 nT/Hz w/FC’s Operating T RT Form Factor 0.001 mm3 chip Power battery B I InAs thin film Applications Keyboard switches Brushless DC motors Tachometers Flowmeters Commercial: ~$ 0.1  1 Disruptive - hybrid

35 Disruptive technologies? Superconducting flux concentrator
Hybrid S.C./GMR State variable GMR voltage B-field Vector 1 Hz 32 fT/Hz Operating T cryogenic Volume 0.1 cm3 Power Battery Field Gain YBCO ~ 100 Nb ~ 500 “…An Alternative to SQUIDs” Pannetier, et. al, IEEE Trans SuperCond 15(2), 892 (2005) ME

36 Magneto-electric H Magnetostrictive + piezo-electric multilayer
State variable Piezo voltage B-field Vector 1 Hz sources 1 nT/Hz pyro/static Operating T -40 to 150C Volume 1 mm3 Power H PMN-PT VME Terfenol-D Disruptive No power required Two terminal device High impedance output Dong, Zhai, Xin, Li, Viehland APL V86, (2005). MO

37 Magneto-optic Magnetometer head State variable Light intensity B-field
Mirror-coated iron garnet B Fiber- optic State variable Light intensity B-field Vector 1 kHz 1.4 pT/Hz Operating T ambient Volume 1 cm3 Power line Ferrite Flux Concentrators Light polarization changes in garnet Rotation  B-field (Faraday effect) Sensed with interferometer Disruptive Light not affected by B Remote sensors High speed Imaging capability (light) NDE Deeter, et. al Electronics Letters, V29(11), p 993 (1993). Youber, Pinassaud, Sensors and Actuators A129, 126 (2006). Spintronic

38 More spintronic sensors
Extraordinary MR (EMR) Hall effect with metal impurity Based on 106 MR in van der Pauw disks Non-magnetic materials Mesoscopic device DR/R ~ 35% in field Replacement for GMR in hdds? 220% TMR in 2004 … B Semiconductor Au impurity Au V I InSb 300 nm “Magnetic Field Nanosensors, Solin, Scientific American V291, 71 (2004)

39 Other disruptive technologies
Magneto-strictive delay lines Spintronics: CMR Spin-FET – tunnel junctions Spin-FET – nanowires - APL (2007) concl

40 Compilation Sensor B pt/Hz @ 1 Hz Volume Power
SQUID v .01 1 cm3 Line Proton s 1 battery e- He4/CSAM/SERF s/s/v 1 / 5 / .001 mm3 – cm3 Battery-line Fluxgate 10 GMI 3000 0.01 mm3 MR 200 0.001 mm3 Hybrid GMR/SC .032 .1 cm3 Hall 30,000 ME 1000 1 mm3 Magneto-optic line Trend: Noise increases as Volume decreases

41 Trend of volume vs. noise
Examples: AMR Large arrays of elements, good magnetic properties make up for lower noise Flux concentrators Increase volume  reduced noise floor Fluxgate magnetometers - Sn T ''/ Koch – increase volume and decrease loss in material “Fundamental limits…” Koch et al, APL V75, 3862 (1999) Compare sensors based on volumetric energy resolution Energy resolution  Noise Power  Active magnetic volume D. Robbes / Sensors and Actuators A 129 (2006) 86–93 SQUIDS & SERF technique lead, hybrd GMR/S.C. coming up

42 Conclusions High sensitivity magnetometers research very active
Many advances to be made in conventional devices Potentially disruptive technologies Move to smaller, lower power, nano-fabrication Evalute high sensitivity against many other parameteters: Spatial resolution, power, vector.. Ackn.

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

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