3rd July, 2015

Dr. Eng. Yoshinobu Honkura,President 1Magnedesiｇn incorporation, Japan

Vice president Magnetic society of Japan

The study on electromagnetic coupling with amorphous wire and micro coil excited by GHz pulse current

Outline

1. Background

2. The study on Micro coil performance excited by GHz pulse

3. Discussion on GHz-Spin-Rotation Effect(GSR)

4. Future scope and Summary

the International Workshop on Magnetic Wires, IWMW 2015, Ordizia 203 July

Backgrond: Development History on GMI Sensor

amorphous

wire

20μ

human hair

150μm

Prof. Masumoto Prof. Mohri

research of

Amorphous Wire

invention of

MI sensorDevelopment of

Micro coil

excited by GHZ pulse

Electronics compass

2×2×1㎜

0.9mm×0.5mm

Amorphous Wire 20μ

Development of

MEMS type MI element

MI sensor circuitFe-Co base Amorphous wire

Production of E-compass

Based on GMI sensor Study of Amorphous Wire

90 95 00 0580 85

Develop of GMI Sensor

MEMS type GMI elemnt

10

Discovery of

MI sensor

With Amorphous ribbon

Prof. Makhotkin

In USSR

0.20mm

0.2

5m

m

15

More sensitiveMore micro

MEMS type MI element

Honkura

MAGNEDEZIGN

Micro coil type MI element

MI Sensor

Aichi Steel AMI306

MI Sensor

Aichi Steel AMI307

GMR Sensor

ALPS HSCDT004A

TMR Sensor

Freescale MAG3110

Hall Sensor

ASAHI KASEI AK8975

GMR Sensor

YAMAHA YAS530

-10

-8

-6

-4

-2

0

2

4

6

8

10

0 60 120 180 240 300 360

Azimuth [degree]

Azi

muth

Accura

cy

[deg.

]

Accuracy : ±1.1°resolution: ±0.8°

Accuracy : ±1.9°resolution: ±0.5°

-10

-8

-6

-4

-2

0

2

4

6

8

10

0 60 120 180 240 300 360

Azimuth [degree]

Azi

muth

Err

or

[degre

e]

Accuracy: ±0.6°resolution: ±0.4°

Accuracy : ±0.３°resolution: ±0.3°

-10

-8

-6

-4

-2

0

2

4

6

8

10

0 60 120 180 240 300 360

Azimuth [degree]

Azi

muth

Acc

ura

cy [

degre

e]

-10

-8

-6

-4

-2

0

2

4

6

8

10

0 60 120 180 240 300 360

Azimuth [degree]

Azi

muth

Accura

cy

[degr

ee]

Accuracy : ±2.0°resolution: ±1.9°

-10

-8

-6

-4

-2

0

2

4

6

8

10

0 60 120 180 240 300 360

Azimuth [degree]

Azi

muth

Accura

cy

[degr

ee]

Accuracy : ±1.1°resolution: ±0.4°

-10-8-6

-4-2024

68

10

0 60 120 180 240 300 360

Azimuth [degree]

Azi

muth

Accura

cy

[deg.

]

Azimuth Accuracy of various type E-compass for Mobile Phone

4

Principle of GMI sensor

0.5GHz 80mA

10ns

0.5 ns

Pulse current Circular aligned spin

Magnetic Field Hex

0.5nm

-2

-1

0

1

2

-6 -4 -2 0 2 4 6

external magnetic field(G)

outp

ut vo

ltage (

V)

±3G

external magnetic field (G)

outp

utvo

ltage

(V)

1

1.2

1.4

1.6

1.8

2

-10 -5 0 5 10

±3G

Magneto-impedance vs magnetic field strength Coil voltage vs magnetic field strength

f: frequency N: coil numbers

The effect of coil turns of pick up coil of MI element

Authorized by Prof. Uchiyama

Coil numbers (turn)

Sensitiv

ity (

v/m

T)

The effect of the frequency of exciting current

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0 １ ２ ３

Frequency (GHz)

Imagin

able

part o

f w

ire im

pedance (

%/Am

-1 )

0.４

Current pulse frequency １GHz

ｔ

impedance Imaginal part of impedance

using big size coil of diameter 3mm Using MEMS type coil of 30μｍ⇒What frequency is best for coil voltage

Measured by Prof. ZhukovMeasured by Prof. Mohri

10MHz is best

0.60mm

0.3

0m

m

Coil turns of 560

Develop the micro coil type of GMI sensor to increase coil numbers

0.40mm

0.2

5m

m

wet processCoil pitch of 30 μm

pT element for detecting bio-magnetism

Micro coil type for e-Compass

Coil turns of 42Coil turns of 16

0.20mm

0.2

5m

m

Coil turns of 42

0.90mm

0.5

0m

m

Aichi Steel type

dry processCoil pitch of 5.5 μm

New Process to produce the micro coil type GMI element

素子の製造プロセス

Principle of MI detection

Pulse currentrising time0.5nsec

Amorphous wire

External magnetic field Hex

Pick up Coil

etching Bottom coil pattern Wire setResin molding

Upper coil pattern

Coil pitch 5.5μm

GrooveW=25μmDepth=6μm

Wire Dia. 14μmSiO2 coating

Resin moldingCoil pitch 5.5μm

Production Process

9

Enlarged view of GMI element with the micro coil

Groove with Bottom coil pattern

Magnified figure with coil pitch of 5.5 μmGroove depth of 6μm

Coil

wireGlass

Enlarged view of Upper Coil pattern

Enlarged view ofBottom coil pattern

Detail section drawing

Aliment precision of <±１μmRotation precision of <±0.02degree

The amorphous wire aliment machine

11

Equipments in use at nanotechnology platform of Nagoya University

Magnetron spattering Equipment RIE etching equipment

Laser rithography Overview of Clean room

type Element Coil Wire

Commercial

MI element

By Aichi Steel

Area

=0.18mm2

Pitch =30μm

Numbers =16turns

Resistance =1.3Ω

Permeability (Hk=20G)

Diameter =11μm

Resistance =6Ω

Micro coil type

Element

By Magnedesign

One-wire

Area

=0.10mm2

Pitch =5.5μm

Numbers =42turns

Resistance =220Ω

Permeability

(Hk=30G)

Diameter =11μm

Resistance =4.5Ω

Two-wire Area

=0.05mm2

Pitch =5.5μm

Numbers =42turns

Resistance =210Ω

Permeability

(Hk=40G)

Diameter =11μm

Resistance =6Ω

pT element

Four wire

Area=0.45mm2 Pitch =5.5μm

Numbers =560turns

Resistance =1850Ω

Permeability

(Hk=40G)

Diameter =11μm

Resistance =61Ω

0.40mm

0.2

5m

m

0.20mm0

.25

mm

0.60mm

0.3

0m

m

0.90mm

0.5

0m

m

the result to evaluate its performance of GMI elements with micro coil

13

Methods for measuring the micro coil voltage

Wire pulse wave

1.2GHz 200mA

Coil voltage wave 40mV/ 1G

Measuring Equipment Pulse current wave

and coil voltage wave

Powersource

GND

Pulse generator

Buffercircuit

Output terminals

GSRelements

EVK board of GMI elementsWith 1.2GHz pulse Oscillo scope

probe

coil voltage wave under various magnetic field

magnetic field

EVK test circuit

Time (nsec)

Coil

voltage (

V)

Buffer circuit

3-1 Effects of current frequency on magnetic sensitivity

1G 10G1M 10M 100M

Se

nsitiv

ity (

mV

/G)

Pluse frequency (Hz)

0

1000

2000Coil pitch of 5.5μm

Effect of Pulse frequency on sensitivity

f = 1/ 2Δt

Δt

time

Cu

rre

nt

Definition of

converted frequency

Commercial

type

GH type

3-2 Effects of coil numbers on magnetic sensitivity

Influence of coil numbers on sensitivity

Coil numbers (Turns)

Mag

neti

c s

en

sit

ivit

y V

/Gu

ss

Sensitiv

ity (

V/G

auss)

Coil numbers (turns)

±0.85V±20G 76mV/Gauss

+0.5

0

-0.5

Coil

Voltage (

V)

External Field (G)

0-20G +20G

3-3 (1) The results of measuring coil voltages for Elements against magnetic field

Commercial

Coil Numbers =16 turns

Micro Coil One-wireCoil Numbers =42 turns

Rising pulse

±0.6V±33G30mV/Gauss

+0.5

0

-0.5

Coil

Voltage (

V)

External Field (G)

0-20G +20G

±0.5V±20G33mV/Gauss

+0.5

0

-0.5

Coil

Voltage (

V)

External Field (G)

0-20G +20G

Rising pulse

±0.25V±40G9mV/Gauss

+0.5

0

-0.5

External Field (G)

0-20G +20G

down pulse (Commercial type)

Coil

Voltage (

V)

down pulse

0.60mm

0.3

0m

m

0.40mm

0.2

5m

m

40mV/G

±0.85V±27G40mV/Gauss

±0.68V±33G26mV/Gauss

3-3(2) The results of measuring coil voltages for Elements

two-wireCoil Numbers =42 turns

立下

0.20mm

0.2

5m

m

0.90mm

0.5

0m

m

four-wire （pTtype)Coil Numbers 560 turns

±1.1V±5G400mV/ G

±0.8V±7G120mV/G

Rising pulse down pulse

down pulseRising pulse

External Field (G)External Field (G)

External Field (G)External Field (G)

Coil

Voltage (

V)

Coil

Voltage (

V)

Coil

Voltage (

V)

Coil

Voltage (

V)

3-3 (3) Summary

18

type CommercialMI element

microOne-wire

microTwo-wire

micropT four-wire

Comparison withmicro vs Mi

Coil numbers turn 16 42 42 560

Wire resistance Ω 6 4.5 6 61

Coli resistance Ω 1.3 220 210 1850

Element size mm2 0.18 0.10 0.05 0.45 3.6 times better

Max Coil Voltage V 0.50/0.25 0.85/0.60 0.85/0.70 1.10/0.80

Measuring Range G 20 / 40 20 / 33 27 / 33 5 / 7

Sensitivity mV/G 33 / 9 76 / 33 40 / 26 400/120 2.9 times better

Current mA 263 (1) 240 263 67

Linearity Range G ±12G ±30G ±30G ±6G 2.5 times bettr

Process (Cost) Wet Dry Dry Dry Half cost

Cost Performance 1 52

Cost performance =Sensitivity＊size＊linearity Range＊Process

E-Compass Medical use

19

Current circuit With Buffer circuit

3-5 The effect of Buffer circuit on coil voltage

We can increase the sensitivity of GMI sensor by the coil numbers but Micro coil is accompanied by the

increase of the coil resistance which makes IR drop and decrease the coil voltage

3-5 The effect of Buffer circuit on coil voltage

Coil voltage decrease about 25% after buffer circuit.Not so big problem but need to develop suitable circuit

40mV/G

30mV/Gauss

two-wireCoil Numbers =42 turns

0.20mm

0.2

5m

mRising pulse

External Field (G)

Coil

Voltage (

V)

converted to arcsin(V/Vo)= πH／2Hm

3-6 new relationship on the output voltage against magnetic field

±12G

±36G

Using the equation , the measuring range can be extended from ±１２G to ±36G.

V=V0sin(πH／2Hm )

-Ｈm +Ｈm

External magnetic field (G)External magnetic field (G)

Co

il vo

lta

ge

(V

)

Co

nve

rte

d C

oil

vo

lta

ge

(V

)

22

If spin rotation with angel of θ on the surface is detected by the micro coil,

Theoretical Eq. :V=Vo・sin(2θ) here tanθ=Hin/Kθ(Hk) ⇒θ is function of HkHin: effective magnetic field

Kθ：the intrinsic circular anisotropy magnetic field of the amorphous wire related to the intrincis logthdinal

anaisotoropy magnetic field Hk .

Experimental Eq. :V=Vo・sin(2φ) φ＝πH/2Hm

⇒φ is function of Hm

two equation are same form

Experimenatal deta and theory sujest :Hm =Hk

theory eq and experimental eq are matched.

θ = φ

Circular spin aliment Magnetic field H

thickness

0.5 μm

α

converted voltage with Vt=arcsin (Vm/Vo)Raw Data

Hm

Co

il v

olt

age

Vm

(V)

Magnetic field H(G)Magnetic field H(G)

Co

nv

erte

d c

oil

vo

ltag

e (V

)

my hypothesis : Why is there V=V0sin(πＨ／2Ｈｍ ) between with V and H ?

1) BH curve of amorphous wire against X direction

Why is there V=V0sin(πＨ／2Ｈｍ ) between with V and H ?

Hk1 Hm1 Hm2Hk2 Hk3 Hm3990℃

980℃

990℃

980℃

Ｍ／Ｍｓ

Field ＨｅｘＯｅ

ＢＨcurve

Curve of coil voltage

ａ）Bh curve of the amorphous wire

Magnetic properties of the amorphous wire have two types as longitudinal direction and circular direction

Coil voltage(ｍＶ)

Hk

β 10%

H

M

Ms

Why is Hk is equal to Hm

2) The coil voltage V vs magnetic field H

ｂ）The coil voltage V vs magnetic field H

V=V0・sin（πＨ/２Ｈｍ）here Hm is defined as the field strength of V max

M= χHχ ≒ χo｛１―β×（Ｈ／Ｈｋ）２｝

Hk is defined as the field strength where the magnetization is caused by from magnetic domain movement to magnetization rotation.Hk is roughly defined as the field of M/Ms=90%.β gives the magnetic susceptibility at H=Hk

χo Χo(1-β）

Hm= αHk (α= 0.96)

When H=Hk, the core domain is saturated and spin in the surface domain reaches to the angle of π/4. If over π/4, the surface domain changes to the core domain. When H>Hk, the core domain extends forward the surface domain and spin angle rotates from π/4 to π/2 . That means when H=Hk, the coil voltage has the max and Hm=Hk.However experimental data shows Hm=0.96Hk. (α=0.96）becuaase the demagnetizing field in surface domain is alittle small compered to the core domain.

tanθ＝（H/Hm）｛α（１－Nχo）＋βNχoα３（H/Hm）２｝／｛1－（1－β）Nχo｝ （２）

Kθ intrinsic internal magnetic fieldHin : internal magnetic field

Spin direction with θ

Spins Rotation with the θ at GHz speed gives V=Vo・sin(π/2×H/Hm）

Frequncy is givenAngular velocity ω＝2πfSpin angle of θ （Mx=M0sinθ）Ms velocity : Vx=M02πfcosθ

1)Experimental Equ. V=V0sin2φ where φ＝ πH/4Hm

2) Theoretical Equ. V=V0sin2θ・ If spins with the angle of θ rotates at the high angular velocity of 2πf、 Coil voltage becomes V=V0sin 2θ.・The reason is;

The flux of x direction: φx= msLDdsinθ=φ0sinθ

The velocity of φx: Vx= 2πfcosθ

The coil voltage V＝－dΦ／dt=－ φx・VxV＝=－φ0・sinθ・cosθ・2πf＝―V0・sin2θ

3)The spin angle of θ is defined astanθ＝Hin/Kθ

Hin＝H｛1－Nχo＋βNχo（H/Hk）２｝4) When H=Hk ,θ=π/4 and Hin=Kθ

Kθ＝{1-(1ｰβ)Nχo}Hk

tanφ＝tan（πH/4Hm）＝(H/Hm){π/4＋1/3×(π/4)３(H/Hm)２ } （１）

5) Comparing with (1) and (2), we can get φ=θIn the case the amorphous wire has α=0.96, and magnetic susceptibility

as Nχo ≒ 1／（1＋4.5β） which gives β=0.04～0.20,Nχo=0.84 ～0.53

Nχｅｆｆ＝1－（χｅｆｆ／χｒ）

θspinKθ

Hin

θ

The result of LLG analysis on the spin movement in the amorphous wire excited by Pulse current with high frequency studied by Dr. Y. Uehara

Magnetic anisotropy energyMagnetostatic energyExchange energyZeeman energy

LLG equation

Bessel equation applied to high frequency current passed through the wire

Manifold equation with LLG eq. and Bessel eq.

CurrentMagnetization distribution Δｍφ

Including eddy current effect

Heff

Hφ is added toHeff

Hθ in duce d by current

Pulse current

Average magnetization mx

Analysis Magnetization on the plane

Applied magnetic fieldX direction

Amorphous wireinfinite

Bessel eq.

0.4

0.2

0

0.6

0.8

1

Curr

ent

(A)

The result of LLG analysis on the coil voltage at the risng pulse and down pulse against various magnetic field

At rising pulse, the coil voltage is induced at the short time and high sharp.

At down pulse, the coil voltage is delayed low and wide.

These data is matched with experimental results.

Rising pulse

Down pulse

Coil Voltage

Pulse Current

The effect of the external magnetic field on the coil voltage by the LLG analysis

These data is matched with experimental results of V=V0sin （πH/2Hm).

The mathematical results derived by GHz pulse can be derived by spin rotation

with GHz speed. So I propose GHz phenomina to be called as GHz-Spin –Rotation

effect. In other words, GSR effect

Like sine function

Comparison with FG sensor, MI sensor and GSR sensor

GSR sensorFG sensor MI sensor Aichi SteelMI sensor

１KHz

１MHz

１GHz

103

1

106

1944

10MHz

200MHz

2GHz

1993 2008 2015

30KHz

Puls

e fre

quency

(Hz)

Perf

orm

ance

ｆ＝ＭＨｚｆ＝ＫＨｚ ｆ＝ＧＨｚ

Performance=K：sensitivity× W:measuring range × D：diameter ×L：wire length

By 1000

By 100

By 10

age

Skin depth 100μm 2μm 0.2μm

Two highlight applications

Biomagnetism Earth magnetism Industrial Magnetism

10-9

(nT)10-12

(pT)10-6

(μT)10-3

(mT)

Nano-particle

1(T)

Weak Field

Strong Field

0.2nT1G1mG

1μG

100,000 smaller sensitivity

CompassWith magnetic Gyro

Pico-Tesla Sensor

0.1

1

10

100

1000

10000

100000

1000000

0.1 1 10 100

Frequency (Hz)

Noi

se d

ensi

ty (

pT/√

Hz)

For AMI306

For AMI307

Target of PT element

Nois

e σ

ΔH（m

G）

0.1 1 10

0.1

1

10

Measuring time ： Δt (ms)

Hall sensor

Semiconductor Magnetometer

Target

AMI306

0.１ｍＧ 0.1ｍsec sampling time 1 ms

MR sensor

MI sensor

GMI301

10,000 better performance

sensitivity,+ speed + size

×100timesbetter

×100００timesbetter

Potentiality of GSR sensor

Bio-Mag

10-10 10-8 10-6 10-4 10-2 100 102 104

1Hz

1KHz

1MHz

1GHz

Gauss

GSRsensor

SQUID

fT pT nT μT mT 1

handy MRI

0Hz

Tesla

Earth Mag

GmGμGnG

Brain heart

MIsensor

FGsensor

Big potentiality on High sensitivity + high frequency + mini size/low cost + low power consumption

magnet-for Car, home appliance

Magnetic fie

ld F

requency

low Magnetic field strength(G) big

Hall sensorMR sensor

compass

Magnetic gyro

31

Summary

１） The sensitivity oｆ GMI sensor can be improved by GHz pulse and micro coil.

２） when using the pulse with 1.2GHz and micro coil with pithch oｆ5.5 μm are used,

GHz GMI sensor (GSR sensor) achieved 40 better performance compared to MI sensor.

３） The coil voltage shows the sine equation as V=V0・sin(２θ) caused by spin rotation.

４） high light Application

・E-compass with magnetic gyro for wearable computer

・ｐT sensor to detect bio-magnetizm applied to Magneto-cardiogram and Magnetoencephalography