Giant Magneto Impedance and Applications M. Vazquez Instituto de - - PowerPoint PPT Presentation

Giant Magneto Impedance and Applications

• M. Vazquez

ESM 2007, Cluj-Napoca, Romania

Instituto de Ciencia de Materiales de Madrid, CSIC

ESM 2007, Cluj-Napoca, Romania Giant Magneto Impedance and Applications

a) Introduction.- What is Magnetoimpedance?, its origin? General Definitions b) GMI and Magnetization Process.- Materials; Magnetic Anisotropy; “Single Peak” and “Double Peak” behavior, Stress-impedance c) Advances in GMI: New soft materials; Developping sensors based in GMI

References

• “Giant Magnetoimpedance in soft magnetic wires”, M. Vázquez, J. Magn. Magn. Mat. 226-230 (2001) 693-699.
• "Giant Magnetoimpedance", M. Knobel, M. Vázquez y L. Kraus Handbook. Handbook of Magnetic Materials, ed. K.H. Buschow,
• Vol. 15. Chap. 5, pp. 1-69, Elsevier Science B.V. 2003.
• " Giant Magnetoimpedance: Concepts and Recent Progress", M. Knobel y K.L. Pirota, J. Magn. Magn. Mat. 242-245 (2002) 33-39.
• "Soft Magnetic Wires", M. Vázquez, Physica B 299 (2001) 302-313.
• " Giant Magnetoimepdance as a tool to measure properties of materials", M. Knobel, J. Phys. IV France 8 (1998) Pr 213-218.
• "Giant Magnetoimpedance effect in soft amorphous and nanocrystalline ribbons", ML Sánchez, VM Prida, B. Hernando, M.

Tejedor and M. Vázquez, Recent. Res. Devel. Magnetics 3 (2002) 191-201.

• “Hysteretic behaviour and Anisotropy fields in the magneto-impedance effect”, M. Vázquez, J.P. Sinnecker and G. Kurlyandskaya,

Materials Science Forum 302-303 (1999) 209-218.

• "Giant magnetoimpedance effect in soft magnetic wires for sensor applications", M.Vázquez, M.Knobel, M.L.Sánchez, R.Valenzuela

and A.P.Zhukov, Sensors and Actuators A59 (1997) 20-29.

• “International Workshop on Magnetic Wires” San Sebastián 2001. J. Magn. Magn. Mat. Vol. 249 (2002) (whole issue)
• Magnetic Sensors and Magnetometers, P. Ripka and L. Kraus ed. Artech House, 2001, pp 349-367
• Kamruzzaman Md., I.Z. Rahman, J. Mater Proc Techn. 119 (2001) 312
• M. Knobel and K. Pirota, J. Magn. Magn. Mater 242-245 (2002) 33

ESM 2007, Cluj-Napoca, Romania Giant Magneto Impedance and Applications

Soft Materials : Ribbons, Wires and Microwires for sensors

Microwire CoFeNi(SiB) glass coated Amorphous wire 20- 100 µm (Unitika) melt spinning Process ≈ 1 mm

rotating copper wheel as quenched ribbon RF heating coil

Rotating wheel :

Amorphous (Fe or Co based), Nanocristalline

Water Cooled Microwires :

Amorphous (Fe or Co based)

Classical Wire drawing :

Cristalline NiFe mumetal

Soft amorphopus wires obtined by rapid solidification techniques

Amorfo wire, FeSiB, 10 cm in length 120 µ µ µ µm diámeter

• 0 ,2
• 0,1

• 1,00
• 0,75
• 0,50
• 0,25

H (Oe )

• 250
• 200
• 150
• 100
• 50

• 0.0015
• 0.0010
• 0.0005

M (E.M .U .) H (A/m)

Glass-coated microwire FeSiBC, coated by Pyrex, 2 mm in length 10 µ µ µ µm diameter

Glass-coated microwires: Fabrication by rapid solidificatio (106 K/s) Metallic ferromagnetic nucleus (0.6-30 micron diameter) Pyrex coating( 2-20 micron thick) Continuous Production (400 m/min, 1 kg-40.000 km)

5 micron

Magnetization process by a single Barkhausen jump Composition: FeSiB (λ λ λ λs≈ ≈ ≈ ≈+3x10-5), CoFeSiB (λ λ λ λs≈ ≈ ≈ ≈-1x10-7) CoSiB (λ λ λ λs≈ ≈ ≈ ≈-2x10-6)

Amorphous wire FeSiB

(positive and large magnetostriction) Amorphous wire obtained by rapid solidification into rotating water: ∼ ∼ ∼ ∼ 100 µ µ µ µm diameter

Under which conditions a wire is magnetically ultrasoft?

Easy to remagnetize Low magnetic anisotropies Minimum Magnetocrystalline anisotropy⇔ Amorphous or nanocrystalline structure Mínimum Magnetoelastic Anisotropy, Emelas≈ (λsσ)⇔ Non-magnetostrictive, Mínimum stresses

Alloy Composition: (Co94Fe6)75Si15B10 Magnetostriction: -1x10-7 Hysteresis Loops: Coercivity ∼ ∼ ∼ ∼ mOe !! Axial Circular

Domain structure

Non-magnetostrictive Amorphous Wire

What is Magnetoimpedance?

It consists of the large modificatio of Impedance (real and imaginary components) of a magnetic conductor magnético at the presence of changing static magnetic field

High field Sensitivity ≈ ≈ ≈ ≈ 500% /Oe Low static magnetic field Hmax ≈ ≈ ≈ ≈ 1-10 Oe Observed in soft Magnetic Materials

GMI phenomenology

• 8
• 4

4 8 1 2 3 4 5

f = 500 KHz (Fe0.06Co0.94)72.5Si12.5B15 Iac = 1 mA Without applied stress

|Z|/Rdc H (kAm

• 1)
• 8
• 4

∆Z/Z % H (kAm

• 1)
• 8
• 4

4 8 20 40 60 80 100 120 140 160

[Ohms] H (kAm

• 1)

R X |Z|

• 8
• 4

4 8 1.0 1.5 2.0 2.5 3.0

f = 500 KHz (Fe0.06Co0.94)72.5Si12.5B15 I = 1 mA Applied stress

σ = 133 MPa

|Z|/Rdc H (kAm

• 1)
• 8
• 4

• 1)

Variation of real and imaginary Components of Impedance Z=R+iω

ω ω ωX GMI definition Z(H)   /Rdc ∆ ∆ ∆ ∆Z/Z(%)=[Z(H)-Z(Hmax)]/Z(Hmax) Different Behavior: “Single Peak” y “Double Peak” Dependence on exciting frequency

Amorphous CoFeSiB wire

Families of Materials exhibiting GMI

First Publications:

Harrison et al. Nature (1935), Makhotin et al. Sensors and Actuators (1991), Mohri et al. IEEE Trans. Magn. (1993), Machado et al. J.

• Appl. Phys. (1993), Mandal & Ghatak Phys. Rev.B (1993), Velázquez et al. Phys. Rev. B (1994)

Rediscovering GMI in Amorphous Wires: Panina & Mohri, Appl. Phys. Letter (1994), Beach & Berkowitz, Appl. Phys. Letter (1994) Large number of initial publications in other materials during the 90’s:

Amorphous ribbons (Machado et al., Sommer & Chien, Tejedor et al.) Nanocrystalline alloys (Knobel et al., Chen et al.) Thin films (Panina & Mohri, Sommer & Chien) Sandwichs Metal/Insulating (Morikawa et al., Antonov et al.) FeSi (Carara&

Sommer) Permalloy fibers (Ciureanu et al., Vázquez et al.) Mumetal (Nie et al.) Electroplated microtubes (Beach & Berkowitz, Sinnecker et al.) Amorphous microwires (Vázquez et al., Chiriac et al., Zhukov et al.)

Impedance and skin effect

The skin effect is very intense in amorphous alloys owing to their high permeability and resistivity δ << a ℓ ℓ δ 2 π a Z ≈ R ≈ ρ ℓ / (2πaδ) ≈ f1/2 µ1/2 φmin ≈ 0.5 µm

Origin of GMI: the skin effect

(a problem: the non-linearity of permeability)

Dificulties for quantitative estimation of δ : in ferromagnetic materials permeability, µφ, is not linear function First approximation: taking < µφ > Introducing the magnetization process in the skin effect: i) Radial profile of internal stresses (Km.elást) and magnetic hystory (Kind) ii) Influence of the amplitude (Iac) and frequency (f ) of current or circular field (Hφ)

The static field, Hdc, reduces the circular permeability, µ µ µ µφ

φ φ φ,

and increases the skin effect penetration depth, δ δ δ δ, so reducing the impedance, Z

Determining experimentally GMI

( ) ( )

z z ac L L ac z z q q

e S dz j S dz U Z I j dq j dq ρ = = =

∫ ∫ ∫∫ ∫∫

ac R L dc ac i ac

U U iU R I i L I ω = + = +

( ) ( )

S S

t t

h n e × =ζ ˆ

        − =

φ φ

ζ ζ h h l L Z

z z zz

Impedance tensor

ac dc i ac

U Z R i L I ω = = +

f<< (no skin

effect)

Magnetoinductive effect

Careful with the measuring process!: Is there too many cables?

Measuring through the four points technique

Muestra I V

I V Z =

Impedance network analyser: authomatic cancelling of parasitic impedances

200 400 600 800 1000 1200 1400 5 10 15 20 25 30

f (MHz) GMI (%)

GMI-Z GMI-R

Eliminating parasitic resistence but not capacities/autoinduction of cables

200 400 600 800 1000 1200 1400 2 4 6 8

f (MHz) GMI (%)

0 m 1 m 2 m 4 m

C (pF) (line length) Experimental Frequency (MHz) Theoretical Frequency (MHz) 100 (0 m) 4 5.0 200 (1 m) 3 3.5 300 (2 m) 2.5 2.9 500 (4 m) 2 2.2 1600 (15 m) 1 1.2

Low frequency: resonance with parasitic capacitance

500 1000 1500 2000 2500 3000 10 20 30 f (MHz) GMI (%) 0 m 1 m 2 m 4 m

High frequency: analysis though transmission lines: stationary waves (maxima and mínima in voltage)

Longitudinal Magnetic Anisotropy: “Single-Peak” like GMI

Hdc (Oe) Z(Ω Ω Ω Ω)

Magnetization process by rotation

Under the circular alternating field magnetization rotates around the axial direction

Correlatio between GMI and magnetization process Fine structure of double peak: irreversible magnetization process

f =3.7 MHz

Circular Magnetic Anisotropy: “Double Peak” like GMI

Circular Anisotropy, Wall bending Magnetization Rotation

rot dw φ φ φ

µ µ µ = +

CoFeSiB amorphous wire after thermal stress-annealing inducing circular anisotropy (correlation GMI & Magnetization Curves)

Transverse anisotropy induced by thermal field-annealing (C1,C4) and stress-annealing (C2,C3) (FeSiBCuNb Nanocrystalline)

Hac(circ)<Hk<Hdc(long)

µ µ µ µt and GMI maxima at Hdc=Hk

Hk

• 8
• 4

4 8 1.0 1.5 2.0 2.5 3.0

f = 500 KHz (Fe0.06Co0.94)72.5Si12.5B15 I = 1 mA Applied stress

σ = 133 MPa

|Z|/R

H (kAm

• 1)
• 8
• 4

• 1)

Applied static field, Hdc, tries to overcome intrinsic circular anisotropy, Hk Hdc

ESM 2007, Cluj-Napoca, Romania

Theoritical description : Easy axis

HK = 2 K / JS

(a) (b) (c)

= dc magnetization H0 > HC : M0 = MS H0 >> HK : χt rot = 2 MS / H0

GMI hysteresis

Nanocrystalline FeSiBCuNb wire after stress annealing Correlation between hysteresis of magnetization process and GMI

Hk ≠ ≠ ≠ ≠ Hirrev

Hysteresis extends to region

• f irreversibilities of

magnetization process

Magnetoelastic effects and their applications

• 100
• 50

50 100 100 200 300 400 50 100 150

∆

Z / Z %

σ (MPa)

H (Oe)

s s ind m

M H H 3 µ σ λ + =

Hind = 3.46 kA/m, λ λ λ λ s = 1.42 x 10-6

Nanocrystalline wire Fe73.5Cu1Nb3Si13.5B9 After treatment under dc current and tensile stress (30 s, 50 A/mm2, 135 MPa)

• 6
• 3

3 6 10 20 30 40 50 H (kA/m) σ (MPa) 44 177 275 Z (Ω) 100 200 300 2 3 4 experiment fitting Hm (kA/m) σ (MPa) Transition from “Single Peak” to “Double Peak” by applying tensile stress (Inducing circular anisotropy) Amorphous wire de FeCoSiB (λ λ λ λs≈ ≈ ≈ ≈-1x10-7) Determination of induced anisotropy Hind, and of magnetostriction λ λ λ λ s by applying mechanical stress

Hk= Hint + Hmelas=(Hk0+Hind)+3λ λ λ λsσ σ σ σ/µ µ µ µ0Ms

Tenso-impedancia

Stress impedance: Variation of impedance with applied stress

• 20
• 10

10 20 30 50 100 150 200 250 300

as-cast tann=1 min tann=5 min tann=15 min tann = 105 min

∆Z/Z

ξ ( %)

ξ (π rad/m)

Helicoidal anisotropy induced in a microwire, CoFeSiB, by torsion annealing

∆ ∆ ∆ ∆Z/Z(%)=[Z(t)-Z(tmax)]/Z(tmax) t = tensile stress (σ σ σ σ), torsion (τ τ τ τ)

5 10 15 20 25 10 20 30 40 50 60 Z

• 1

experiment fitting

Zξ (Ω) ξ (rad/m)

• 8
• 4

4 8 100 200 300

S1 H (kA/m) ∆Z/Z (%)

ξ (rad/m) 0.88 10.5

• 0.88
• 10.5

Dependence on torsion of GMI in a nanocrystalline wire Fe73.5Cu1Nb3Si13.5B9 2 / 1

−

+ = ξ

ξ

q p Z

Torsion-Impedance: its fitting to a model

Example: Torsion impedance

Can GMI behavior be asymmetric?

Asymmetry appears when there is a preferred sense to the excitation of the dc axial field That can be induced by: a) Polarization under additional DC current + Intrinsic Anisotropy (helicoidal) b) Unidirectional Exchange Anisotropy (oxidation produced at the surface during thermal treatment at the presence of H)

• 12 -9
• 6
• 3

3 6 9 12 5 10 15 20 25 30

(a) 0.1 MHz

∆Ζ/Ζ (%) ∆Ζ/Ζ (%)

• 12 -9
• 6
• 3

3 6 9 12 20 40 60 80 100 120

(b) 0.5 MHz

• 12 -9
• 6
• 3

3 6 9 12

• 20

20 40 60 80 100 120 140

(c) 1 MHz Magnetic field (Oe)

• 12 -9
• 6
• 3

3 6 9 12 5 10 15 20 25

(d) 10 MHz Magnetic field (Oe)

Asimmetry induced by Unidirectional exchange (Annealing under axial field) Asimmetry induced by biasing current

Damping of domain walls with high frequency of exciting field

500 kHz 70 kHz

Hysteresis reduced by increasing the frequency that reduces movility of walls

FeCoSiB amorphous ribbons thermally treated to induce transverse anisotropy

GMI in novel materials: magnetic coatings

Coating of Co90P10 (2 to 22 µ µ µ µm thick on a Cu wire 200 µ µ µ µm diameter

20 40 60 80 100 2 4 6 8 10 12

X R

Z (

Ω

)

f (M H z)

Anisotropía Transversal Hk ≈ ≈ ≈ ≈ 6kA/m

Determinating domain structure through Impedance & MFM

• 3 0
• 2 0
• 1 0

∆Z/Z [%] A p p l i e d F i e l d [ k A / m ]

5 0 k H z 5 0 0 k H z 1 M H z 1 0 M h z ∆R/R [%]

C o

7 . 1 µ m I = 1 m A ∆X/X [%]

High GMI response

Image MFM: 12.5 µ µ µ µm x 12.5 µ µ µ µm distance tip-surface: 25 nm Scheme of domain structure observed by MFM

Skin effect reaches the closure domains at δ≈ δ≈ δ≈ δ≈2.4mm

GMI novel materials: microwires coated by glassy cover

500 1000 1500 2000 200 400 600

f=10MHz

ρ=0.98 ρ=0.816 ρ=0.789

magnetoimpedance ratio ∆Z/Z, (%) axial magnetic field H (A/m)

Importance of specific geometry GMI in treated microwires

• 4
• 2

2 4 100 200 300 400 500

Current annealing 40 mA 30 MHz Iac = 1mA

∆Z/Z(%)

Hdc(Oe)

As cast 2 min 4 min 10 min

ρ ρ ρ ρ=Rmet/Rtot

• 400

400

• 1,5
• 1,0
• 0,5

0,0 0,5 1,0 1,5

a

µ0M(T)

• 400

400

• 1,0
• 0,5

0,0 0,5 1,0

c

• 400

400

• 1,5
• 1,0
• 0,5

0,0 0,5 1,0 1,5

b

• 400

400

• 1,0
• 0,5

0,0 0,5 1,0 d

H(A/m)

Histeresis loops

Static field Sensors based on GMI

Idc V Amorphous wire Copper Plate (a)

DC current sensor (Power Electronics)

a) b)

DC magnetic field Sensor (Biomedicine)

Sensors based on en GMI and stress

Sensor de flujo/presión (Electrodomésticos)

1 2 3 6 7 8 9 10

AC Voltage (V) P (g)

AC power source V HDC field Sail Microwire Air flux

200 400 30 60 90 120 150 without stress P=0.72 g P=1.44 g P=2.16 g P=2.88 g

∆Z/Z (%)

H (A/m)

a) b ) c)

Radiodetector de tensiones mecánicas (Automoción)

Cu Layer Substrate Sputtered CoFeSiB soft amorphous / Permalloy

M Idriving

Sensors for Thin Film technology

Scheme of sensor type “sandwich” prepared by “sputtering”

“Single Layer” film, or “Sandwich” F/M/F like structure: i) Suitable for integration in microtechnology ii) Reduced size (few micron) iii) Magnetically harder of sensing element

(b) V t (a)

Magnetoelastic signature pen (Secutity)

• 0,06
• 0,04
• 0,02

F irm a O rig ina l

F a ls ific a c ió n

Authentic Signature (Kleber Pirota) Falsified siganture (Kleber Pirota)

• 0,06
• 0,04
• 0,02

• 500

• 0,08
• 0,06
• 0,04
• 0,02

Tension (u.a.) Tiempo (s)

• 1000
• 500

• 0,06
• 0,04
• 0,02

• 500

• R. Varga
• K. García
• M. Vázquez

Fourier Transform

Sensors based in Stress Impedance

Change of Impedancia with applied stress when signing

Principle of work Head length (m) Resolution full scale (Am-1) Response speed (Hz) Power Consumpti

• n (W)

Hall 10~100 ×10-

6

40 /± 8×104 106 10-2 Magnetoresistence (MR) 10~100 ×10-6 8 /± 8×103 106 10-2 Giant Magnetoresistence (GMR) 10~100 ×10-

6

0.8 /± 1.6×103 106 10-2 Fluxgate 10~20 ×10-3 8×10-5/± 2.4×102 5 ×103 1 SQUID 10~20 ×10-3 50×10-12/ ± ± ± ± 1×10-6 5 ×103

• Magnetoimpedance

1~2 ×10-3 8×10-5/± 2.4×102 106 5×10-3 Stressimpedancia 1~2 ×10-3 0.1 / 30 104 5×10-3

Families of Sensors

Giant Magneto-Impedancia: Summary

Origin: Skin effect

(tecnologically not wished in general)

Materials: Magnetically Ultrasoft

(advanced fabrication, processing techniques)

Tendencies:

Materials: Magnetic coatings, Integrated microelements Frequency Range: Radio to Microwave Micromagnetism: Non-linear, GMI tensor Applications: Optimized Sensors, Integrated Technology

GMI

New branch of research Classical Electrodinamics Processing of materials Micromagnetism Thecnología of Sensors and Integration