Soft Materials and Applications

Soft Materials and Applications O. Geoffroy Grenoble Electrical Engineering (G2Elab)

Materials Application Fields Transformation of Energy Actuation Recording Magnetic Properties Soft Hard Coupling properties Sensors and EAS Magneto-Mechanic Magneto-caloric Magneto-optic

Soft Materials : Some General points * The wold of soft materials : a Schematic view * Basic properties and application fields * How does it work? (Static) * The different permeabilities * How does it work? (Dynamical) Massive, Stacked laminated sheets, wounded ribbons, compacted composites The different frequency ranges * f < 1000 Hz : Classical laminated SiFe, CoFe and futur challenges * 400 Hz < f < 100 khz : Iron based amorphous ribbons * 1000 Hz < f < 100 GHz : Soft ferrites The Vanishing anisotropies alloys * What does it mean? * How do we do? * How tayloring the shape of the loop : The induced anisotropies K u * Transverse K u, flat loops and coherent rotation magnetization mechanism The Very low permeabilities and Energy storage * The classical way : Soft ferrite + Air Gap * The Soft Composites Ribbons, wires and microwires for sensors * The Giant Magneto-Impedance * Electronic Article Surveillance ( harmonic systems, Acousto-magnetic labels )

Metrology K 1, λ s Vanishing anisotropies highest permeabilities Taylorded loops Unipolar electronics Protection Filtering Energy Actuation Power Electronics Special Properties T C Elasticity Thermal expansion Macroscopic : e > 50 µm Massive, laminated Particles + compaction Staked or wounded ribbons Dynamical behaviour frequency range Soft Materials Low dimensions : e 20 µm Particles, Wires, Ribbons Individually Wires Ribbons Sensors K 1, λ s

Soft Materials Materials and Applications transformers drive the magnetic flux i 1 e 1 n 1 φ n 2 S l e 2 Magnetic Shields Flux detection Concentration in air gaps Electromagnets Magnetic forces Machines Actuators Sensors, fault circuits breakers H - F Β e I stator rotor

Soft Materials : the mirror effect Magnetic inductor Soft yoke : µ H yoke = 0 σ yoke ~ J H out = 0 (shielding ) Air gap : B r 0, B θ 0 B r 0, -B θ 0 2 B r 0 The ideal soft Material : µ J s Iron based alloys : µ rfe 8000 J s Fe = 2.2 T

Soft Materials : the different permeabilities µ a, µ i, µ dyn apparent intrinsic B = µ i H Counter field due to eddy currents B = µ a H a = µ i ( H a H j ) applied 1/µ a = H / B + H j / B 1/µ a = 1/µ i + 1/µ dyn static dynamic µ a inf(µ i, µ dyn )

Soft Materials under dynamical regime : Transformation of energy, actuation, power Electronics Classical eddt-currents conductivity e < δ = ( µ i σ π f ) -1/2 skin depth thickness P vclas = 0.167 σ B m 2 e 2 π 2 f 2 Main mechanism : Domain Walls e H a F J S 4 l F a <F> = F a µ dyn = v j π 2 16 l e σ 1 f P v = 1,628 P vclas 2l / e σ (material) e (Process) l (treatments)

Soft Materials under dynamical regime : f < 1000 Hz σ e l 800 ( C) 760 720 680 kj/ m 3 40 20 l (treatments) J s T C K 1 λ 100 0 0 2 4 6 % Si (weight) Laminated SiFe alloys ρ ρ Fe = 10 µωcm ρ FeSi3% = 48 µωcm 2.2 (T) 2.0 1.8 60 µω cm 40 20 10-6 0 CVD enrichment after lamination Lamination : e min ~ 50-100 µm Stacked or wounded magnetic circuits Laser irradiation, Plasma etchching

Soft Materials under dynamical regime : f < 1000 Hz Challenges for the next years : the in-board machines Until now : Electromagnetic ; Hydraulic In the next future : All Electromagnetic Specific power Electrical generation (alternators) Ω Mechanical stress Tensile Strenght : 500 700 GPa alternators directly set in the jet engine : Operating temperature T : 220 400 C Transformers J f (400 Hz 900 Hz) Acoustic noise Vanishing λ 100 New CoFe alloys CoFe alloys ; new dedicated insulation 6% SiFe alloys

Soft Materials under dynamical regime : 400 Hz < f < 100 khz magnetism Glass former Iron based amorphous ribbons : Fe 81 B 13.5 Si 3.5 C 2 resistivity A T Liquid dt dt > 10 6 K / s Planar flow casting C B Amorphou s Cristal D t n t Thickness e ~20-40 µm ρ ~ 140 µω cm (ρ FeSi ~ 48 µω cm) J S ~1.6 T Operating Temperature : 150 C Medium frequency range

Soft Materials under dynamical regime : f > 100 khz Soft Ferrites Very cheap, ρ J S (J S MnZn ~ 0.4 T) Powder compaction sintering massive cores Spinels : Garnets : ρ MnZn ~ 1 Ω m fmax ~ 1 MHz R F ρ NiZn ~ 10 5 Ω m fmax ~ 100 MHz ρ YIG ~ 10 10 Ω m fmax ~ 100 GHz (microwaves)

Soft Materials : vanishing anisotropies alloys : highest permeabilities and taylored loops µ i : static magnetic shielding, low voltage circuits breakers, filtering inhomogeneities µ i = J S / ( b + K 1 + K u + 3/2 λσ ) 1/2 magnetocristallne induced magnetoelastic About inhomogeneities : bubbles H = ε B H B H b Vanishing K 1 Vanishing λ

Soft Materials : vanishing anisotropies alloys : b Vanishing K 1 process disordered structure : Amorphous, Nanocristalline solid solution (NiFe alloys) 100 K 1, 100 Ku Ni % Vanishing λ composition evolution of K 1, Ku for NiFe alloys 40 20 0 10 6 λ λ111 λ 100 40 50 60 70 80 Ni % 22 20 18 16 14 12 10 8 6 4 2 0-2 evolution of λ 100 and λ 111 for NiFe alloys 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 10 6 λs evolution of λ in Nanophy with the cristaline fraction Annealing temperatures 490 C 510 550 530 570 fc The winners : Co based Amorphous Fe based Amorphous Nanocristalline (Finemet, Nanoperm, Hitperm ) Ni 80 Fe 15 Mo 5 Permalloy

Soft Materials vanishing anisotropies alloys : taylored loops and induced K u Heat treatment diffusivity Materials and Applications Vanishing λ, K 1 isotropy effect of a stress applied during the cristallisation flash annealing on a soft nanocristalline alloy K u > 200 J/m 3 mechanical stress magnetic field B (T) 1 0.5 induced K u 0 3000 H (A/m) σ = 0, 10, 40, 120, 270 MPa Rectangular loops : magnetic amplifiers, fluxgate sensors Flat loops : µ r = J S2 / (2 µ 0 K u ) ground fault circuits breakers, Unipolar electronics (pulse transformers ) K u < 200 J/m 3 different shapes (rectangular, flat, round) obtained on Nanophy applying a magnetic field during annealing 1.0 0.5 0.0-0.5-1.0 B / B m H an Long. H an nul H an Transv. H anl H a / H am H ant -1.0-0.5 0.0 0.5 1.0

Soft Materials Flat loops Materials and Applications Energy storage K u Vanishing K 1, λ, alloys : Permalloys, Co based amorphous, soft nanocristalline 2 000 < µ r < 200 000 Field annealing 500 < µ r < 2 000 Stress annealing u u if 0 t E = ½ L I 2 f = ½u 2 t 2 / L L µ µ 0 ra E µ ra 10 < µ r < 500 Classical : soft Ferrite + Airgap e CR : DW : θ H a µ dyn = 1 e µ dyn = 1 e J S 2 µ σπ π 2 16 l σ 1 f 1 f Coherent rotation mechanism Dynamical properties B µ 0 µ r H µ r 10000 B µ 0 µ ra µ ra H a

Soft Materials Soft Magnetic Composite materials : 10 < µ r < 500 Energy storage : High induction Ni Fe Co alloys suitable for high frequency range (10 khz < f < 100 MHz) homogeneous Distributed air gap Enclosed eddy-currents H a Damaging leakage flux at high f No Damaging leakage flux R 20 µm f < 1000 Hz : Moulding possibility 3D geometries µ r 800 Mechanical strengh

Soft Materials Soft Magnetic Composites: Manufacturing process Materials and Applications B ( T ) Fe powder H ( A / m ) B ( T ) H ( A / m ) Fe powder No lubricant : isolating layer destroyed lubricant : isolating layer preserved 1024 µ 512 rm mean field theory 256 (µ Cluj r = 1000) 128 (mechanical 64 alloying) 32 16 8 4 f 0.4 0.6 0.8 1.0

Soft Materials : Ribbons, Wires and Microwires for sensors RF heating coil rotating copper wheel as quenched ribbon melt spinning Process 1 mm Amorphous wire 20-100 µm (Unitika) Microwire CoFeNi(SiB) glass coated Rotating wheel : Amorphous (Fe or Co based), Nanocristalline Water Cooled Microwires : Amorphous (Fe or Co based) Classical Wire drawing : Cristalline NiFe mumetal

Soft Materials : Materials and Applications Ribbons, Wires and Microwires for Giant Magneto-Impedance Principle : Complex Domain Structure depending on λ s B = H / µ c circular µ Inhomogeneous stress j M.I. E = ρ j + E' Inhomogeneous cooling rate Quenching process Domains in a microwire: λ s > 0 (a), λ s < 0 (b) j H H 0 f Z = Lω ~ µ C DW H 0 = 0 DW + rotation µ C = f(h 0 ) Field sensor f Z = R ~ δ ~ µ C -1/2 Z/Z (%) = f(h 0 ) microwire CO 68.25 Fe 4.5 Si 12.25 B 15

Soft Materials : Ribbons, Wires and Microwires for Electronic Article Surveillance Principle : Basic R.F. labels transmitter receiver Rewritable labels Harmonic labels label Magneto Acoustic labels

Soft Materials : Materials and Applications Ribbons, Wires and Microwires for Electronic Article Surveillance Harmonic labels Harmonic response content = shape dependent B / J S u 1.0 0.8 0.6 0.8 0.6 flat loop rectangular loop 0.4 0.2 0.0 flat loop rectangular loop H a / H am 0.00 0.25 0.50 0.75 1.00 flat loop rectangular loop t 0.4 0.2 f / f 0 0.0 0 1 2 3 4 5 6 7 8 9 10 Semi Hard FeCo : 160 A/m < Hc < 800 A/m Co based amorphous ribbon rectangular loop Hc < 1 A/m J = 0 40 mm 1 mm 30 µm

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