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

Giant Magneto Impedance and Applications M. Vazquez 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 RF heating coil rotating copper wheel as quenched ribbon Amorphous wire 20- melt spinning Process ≈ 1 mm 100 µ m (Unitika) Microwire CoFeNi(SiB) glass coated Rotating wheel : Water Cooled Microwires : Amorphous (Fe or Co based) Amorphous (Fe or Co based), Nanocristalline Classical Wire drawing : Cristalline NiFe mumetal ESM 2007, Cluj-Napoca, Romania

Soft amorphopus wires obtined by rapid solidification techniques Composition: FeSiB ( λ λ λ λ s ≈ ≈ ≈ ≈ +3x10 -5 ), CoFeSiB ( λ λ s ≈ ≈ -1x10 -7 ) λ λ ≈ ≈ CoSiB ( λ λ λ s ≈ λ ≈ ≈ -2x10 -6 ) ≈ Glass-coated microwires: Fabrication by rapid solidificatio (10 6 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) Amorphous wire FeSiB 5 micron Amorphous wire obtained by (positive and large magnetostriction) rapid solidification into rotating water: ∼ ∼ 100 µ µ m ∼ ∼ µ µ 0.0015 0.0010 diameter 1,00 0.0005 0,75 M (E.M .U .) 0,50 0.0000 0,25 µ 0 M (T) 0,00 -0.0005 -0,25 -0,50 -0.0010 -0,75 -1,00 -0.0015 -0 ,2 -0,1 0,0 0,1 0,2 -250 -200 -150 -100 -50 0 50 100 150 200 250 H (Oe ) H (A/m) Amorfo wire, FeSiB, 10 cm in length 120 µ µ m diámeter µ µ Glass-coated microwire FeSiBC, Magnetization process by a coated by Pyrex, 2 mm in length 10 µ µ µ m diameter µ single Barkhausen jump

Under which conditions a wire is magnetically ultrasoft? Easy to remagnetize Low magnetic anisotropies Minimum Magnetocrystalline anisotropy ⇔ Amorphous or nanocrystalline structure Mínimum Magnetoelastic Anisotropy, E melas ≈ ( λ s σ ) ⇔ Non-magnetostrictive, Mínimum stresses Non-magnetostrictive Amorphous Wire Alloy Composition: (Co 94 Fe 6 ) 75 Si 15 B 10 Magnetostriction: -1x10 -7 Domain structure Circular Axial Hysteresis Loops: Coercivity ∼ ∼ ∼ mOe !! ∼

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 H max ≈ ≈ ≈ ≈ 1-10 Oe Observed in soft Magnetic Materials

GMI phenomenology 160 140 R GMI definition X 120 | Z | Z(H)   /R dc ∆ Z / Z (%)   200 3.0 f = 500 KHz 150 100 (Fe 0.06 Co 0.94 ) 72.5 Si 12.5 B 15 100 [Ohms] I = 1 mA 80 ∆ Z/Z(%)=[Z(H)-Z(H max )]/Z(H max ) ∆ 50 ∆ ∆ 2.5 0 60 Applied stress -8 -4 0 4 8 H (kAm -1 ) σ = 133 MPa 40 | Z |/ R dc 2.0 20 0 1.5 -8 -4 0 4 8 H (kAm -1 ) 1.0 Variation of real and imaginary Components of -8 -4 0 4 8 Impedance Z=R+i ω ω ω X ω H (kAm -1 ) Different Behavior: “Single Peak” y “Double Peak” 5 400 f = 500 KHz ∆ Z / Z % 300 (Fe 0.06 Co 0.94 ) 72.5 Si 12.5 B 15 I ac = 1 mA 4 200 100 Without applied stress 0 | Z |/ R dc 3 -8 -4 0 4 8 H (kAm -1 ) 2 1 -8 -4 0 4 8 H (kAm -1 ) 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 δ << a δ ℓ 2 π a Z ≈ R ≈ ρ ℓ / (2 π a δ ) ≈ f 1/2 µ 1/2 ℓ The skin effect is very intense in amorphous alloys owing to their high permeability and resistivity φ min ≈ 0.5 µ m

Origin of GMI: the skin effect (a problem: the non-linearity of permeability) The static field, H dc , reduces the circular permeability, µ µ φ µ µ φ φ φ , and increases the skin effect penetration depth, δ δ , so reducing the δ δ impedance, Z Dificulties for quantitative estimation of δ : in ferromagnetic materials permeability, µ φ , is not linear function First approximation: taking < µ φ > Introducing the magnetization process in the skin effect: i) Radial profile of internal stresses ( K m.elást ) and magnetic hystory ( K ind ) ii) Influence of the amplitude ( I ac ) and frequency ( f ) of current or circular field ( H φ )

Determining experimentally GMI = + = + ω U U iU R I i L I ac R L dc ac i ac = = + ω U f<< ( no skin ac Z R i L effect) dc i I ac Magnetoinductive effect ( ) ( ) ∫ ∫ e S dz j S dz z z = = = ρ U ac L L Z ∫∫ ∫∫ I j dq j dq ac z z q q ( ) ( ) = ζ × ˆ e S n h S t t = ζ − ζ   L h φ z   Z Impedance tensor zz z φ   l h  

Careful with the measuring process!: Is there too many cables? Measuring through the four points technique V Z = Eliminating parasitic resistence but not V capacities/autoinduction of cables Muestra I I Low frequency: High frequency: analysis resonance with parasitic though transmission capacitance lines: stationary waves Impedance network (maxima and mínima in analyser: authomatic 1400 0 m voltage) 1 m cancelling of parasitic 1200 2 m impedances 1000 4 m GMI (%) 800 3000 1400 0 m 600 GMI-Z 2500 1 m 1200 GMI-R 400 2 m 2000 1000 GMI (%) 4 m 200 GMI (%) 800 1500 0 600 1000 0 2 4 6 8 400 f (MHz) 500 200 C (pF) (line Experimental Theoretical 0 0 length) Frequency (MHz) Frequency (MHz) 0 5 10 15 20 25 30 0 10 20 30 100 (0 m) 4 5.0 f (MHz) f (MHz) 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

Longitudinal Magnetic Anisotropy: “Single-Peak” like GMI Magnetization process by rotation Under the circular alternating field magnetization rotates around the axial direction Correlatio between GMI and magnetization process Z( Ω Ω Ω Ω ) H dc (Oe) f =3.7 MHz Fine structure of double peak: irreversible magnetization process

Circular Magnetic Anisotropy: “Double Peak” like GMI µ = µ + µ H dc Magnetization φ φ φ ∆ Z / Z (%) 200 3.0 f = 500 KHz rot dw Rotation 150 (Fe 0.06 Co 0.94 ) 72.5 Si 12.5 B 15 100 I = 1 mA 50 2.5 0 Applied stress -8 -4 0 4 8 H (kAm -1 ) σ = 133 MPa dc 2.0 | Z |/ R Circular Anisotropy, H k 1.5 1.0 -8 -4 0 4 8 H (kAm -1 ) H ac (circ)<H k <H dc (long) Wall bending µ µ µ µ t and GMI maxima at H dc =H k Applied static field, H dc , tries to overcome intrinsic circular anisotropy, H k Transverse anisotropy induced by CoFeSiB amorphous wire after thermal thermal field-annealing (C1,C4) and stress-annealing inducing circular anisotropy stress-annealing (C2,C3) (FeSiBCuNb (correlation GMI & Magnetization Curves) Nanocrystalline)