Effect of magnetoelastic anisotropy on domain wall dynamics in amorphous

microwiresV. Zhukova1, J.M. Blanco2, V. Rodionova1,3, M. Ipatov1 and A.

Zhukov1,41Dpto. Fisica de Materiales, Fac. Quimicas, UPV/EHU, 20009 San Sebastian, Spain

2Dpto. de Física Aplicada, EUPDS, UPV/EHU, 200018, San Sebastian, Spain3Moscow State University, Phys. Fac., Moscow

4IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain

Euskal HerrikoUnibertsitatea

eman ta zabal zazu

Universidad del País Vasco

Outline

1. INTRODUCTION 1.1. STATE OF THE ART

2.EXPERIMENTAL TECHNIQUE : -FABRICATION PROCESS

-MEASUREMENTS METHODS 3.EXPERIMENTAL RESULTS

4. Domain Wall Propagation (DWP)4.1. Viscous region

4.2. Effect of magnetoelastic anisotropy4.3. Non-linearity and defects

5. DISCUSSION 6. CONCLUSIONS

Motivation: Proposed

magnetic

memory

and

logic

based

on

DWP

Possible

MRAM and

logic

applicationsStuart

S. P. Parkin, et al. Science 320, 190 (2008); Controlled

and

fast

DW movement

Fabrication

of

Glass

coated

microwires•

Co, Ni , Fe and Cu rich compositions

metalGlass

coating

dmetalDtotal

Fabrication

– UPV/EHU,

andTAMAG, Spain

LG-optimus

ONEAll

models

are manufacturing.

Amount

4x106/month

MI elements

Application in Smart phone using MI sensor with microwLG-optimus

2X

LG-optimus

3D

LG-MS690

LG-LU3100

LG-optimus

chat

LG-optimus

Pad(Tablet

PC)

LG-VS660

SHARP Garmin-ASUS

r

P=Ek(k/3+1)4/3 (1);

z

= P(k+1)+2(k+1)≈3r

(2)

where

r

and

z

-

stresses, Em

, Eg

–

Young

modulus

=(1-

, k =Eg

/Em

, m

g

m

room

–

thermal

expansion

coefficients

and

m

room

–

melting

temperatures

Stress appears at simultaneous solidification of metallic alloy inside the glass coating

H. Chiriac, T.-A. Ovari, A. Zhukov, J.

Magn. Magn.

Mater.

254–255 (2003) 469–471

σ(M

Pa)

t (μм)

K(J

/м3 )

Φ

(μм)

Т

σ=f(ρ), ρ

=d

/D

Internal

stresses

in composite

microwires

Bistable Loops

-250 -200 -150 -100 -50 0 50 100 150 200 250-0.0015

-0.0010

-0.0005

0.0000

0.0005

0.0010

0.0015

M (E

.M.U

.)

H (A/m)

Pyrex coated FeSiBC amorphous microwire

A. Zhukov et al, JMMM(1995)

Schematic presentation of the re- magnetization process

Thin Dimensions: 2 mm long

5 m diameter

MAGNETIZATION PROCESSES IN Fe-RICH THIN MAGNETIC WIRES.

M

H

+

-

++ ---++

+

+ +

- -+++--

-

--

M

H

++ ---++

+

+ +

- -+++--

-

--

M

H

+

- -+++--

-

----

+

++

M

H

M

H

- +--+-- +

++-

--

++

+

++

--

Yu. Kabanov, A. Zhukov, et al, Appl. Phys. Lett. 87 (2005) p142507

Magnetic properties suitable for technologic applications:

-Enhanced magnetic softness and GMI

-Thin Dimensions -Magnetic bistability ( 0) and DW propagation

Pick-up coils

1. Sixtus-Tonks

like

experimentMeasurements technique

t

V=L/t

Nucleation

coil

L

Exciting

coil

Pick up coil

Microwire

0.0 0.5 1.0 1.5 2.0

U2

U1

U 1,U

2(a

.u.)

t (ms)

Sharp peak appears when MW switches

-50 -40 -30 -20 -10 0 10 20 30 40 50

-0,08

-0,06

-0,04

-0,02

0,00

0,02

0,04

0,06

0,08

OscilloscopeHelmholtz

coils

aplicada

Power

Suply

(50 Hz)

R

Sample

Compensation

coil

Pick-

up coil

Fluxmeter

Differences:1-

single layered wounding of magnetizing

solenoid with reduced number of turns for reduction of time of transient process to avoid the situation when the DW can start propagating while H is still growing2-

Use three pick-up coils set to detect

possible multible

DW nucleationM. Ipatov,V. Zhukova, A. K. Zvezdin

and A. Zhukov,

J. Appl. Phys. ,106, 103902, 2009

Kme

3/2 λs

σi

, :λs -determines by the chemical compositionσ= σi + σaσa‘

-

applied stressesσi -determines by the ratio =d/D

Source:

Sources:1. H. Chiriac, T. A. Ovari, and

Gh. Pop, 1995 Phys. Rev. B,

52 10104.2. J. Velázquez, M. Vazquez and A. Zhukov, J. Mater. Res. V.11 No10 (1996) 2499-2505

Hysteresis loops of Fe-rich microwires with different metallic nucleus diameter d and total diameters D: Fe70

B15

Si10

C5

microwires with

ρ

= 0.63, d=15 m (а); = 0.48 d= 10,8 m (b);

=0.26, d= 6 m (c);

=0.16, d= 3 m

(d) and

of

Fe72.75

Co2.25

B15

Si10 microwire with = 0.14, d≈

1.4 μm D≈

10 μm

(f).

-400 0 400-1,5-1,0-0,50,00,51,01,5

-400 0 400-1,0

-0,5

0,0

0,5

1,0-400 0 400

-1,5-1,0-0,50,00,51,01,5

-1000 -500 0 500 1000-1,0

-0,5

0,0

0,5

1,0

-1000 -500 0 500 1000-1,5-1,0-0,50,00,51,01,5

(a)

0M(T

)

(c)

(b)

(d)

H(А/m)

(f) metalGlass

coating

dmetalDtotal

=d/D

0 400 800 1200

500

1000

1500

2000

0 400 800 1200

500

1000

1500

2000

Fe16Co60Si13B11

v(m

/s)

H (A/m)

=0.39

Co41.7Fe36.4Si10.1B11.8

0 200 400 600 800 1000 1200

400

600

800

1000

1200

1400

1600

v(m

/s)

H (A/m)

18m/38m (=0.46)13.6m/34 m (=0.39) 13.6m/24 m (=0.55)

=0.55

=0,46=0.39

v=S(H-H0 )where S is the DW mobility, H is the axial

magnetic field and

H0 is the critical propagation field.

v(H) dependences for Fe16

Co60

Si13

B11

and Co41.7

Fe36.4

Si10.1

B11.8 microwires with ρ=0,39: effect of magnetostriction λs

≈

20x10-6

λs

≈

40x10-6

v(H) dependences for Co41.7

Fe36.4

Si10.1

B11.8 microwires with different ratios :Effect of internal stresses

600 800 1000 1200 1400 1600

600

800

1000

1200

1400

1600

v (m

/s)

H (A/m)

0 MPa 112,5 MPa 168,75 MPa 225 MPa 281,25 MPa 337,5 MPa

v(H) dependences for Fe16

Co60

Si11

B13

microwires (d≈

12m, D≈

m, ≈

0,41 ) measured under application of applied

stresses, app

.

200 300 400 500

400

600

800

1000

1200

1400

1600 0MPa80.5MPa161MPa 241.5MPa 322MPa 402.5MPa 483MPa 563.5MPa

v (m

/s)

H, (A/m)

λs

≈

40x10-6

v(H) dependences for Co41.7

Fe36.4

Si10.1

B11.8 3microwires (d≈

13,6m, D≈

m,

≈

0,55 ) measured under application of applied stresses, a

.

λs

≈

20x10-6

The domain wall mobility, S, is given by: S=s /This damping is related to the Gilbert damping parameter,

and is

inversely proportional to the domain wall width w

,r ≈Ms /w ≈Ms (Kme /A)1/20 40 80 120

0

500

1000

1500

2000

2500

v (m

/s)

H (A/m)

0 MPa 119 MPa220 MPa 440 MPa 660 MPa 880 MPa

v(H) dependences for Co56

Fe8

Ni10

Si11

B16

microwires measured under application of applied stresses, app

.

v=S(H-H0 ), where S is the DW mobility, H is the axial magnetic field and

H0 is the critical propagation field.

Magnetoelastic energy, Kme

, is given byKme

3/2 λs

σ,V(H) is

affected

by Km

λs

≈

10-7

0 50 100 150 200 250 3000123456789

10111213

m = 0.1 g m = 0.2 g m = 0.5 g m = 1.0 g

Nuc

leat

ion

field

(O

e)

x (mm)

Defects

in microwires

Moving nucleation

and

pick-up coil

(far from

ends)

H

M. Ipatov,N. Usov, A. Zhukov et al.. “Local nucleation fields of Fe-rich microwires and their dependence on applied stresses”

Phys. B. 403, 379-381, 2008.

Modified

method

(3 pick-up coils)

0 50 100 150-1000-500

0500

10001500

p3p2

HN, A

/m

location, arb.un.

p1

0 100 200 300 4000

1

2

3

4

5

6

HN2

H, A/m

v, k

m/s

sample 1 sample 2

single DW

multiple DWpropagation

HN1

v=S(H-H0 ) where S is the DW mobility, H is the axial magnetic field and

H0 is the critical propagation field.

On

non-linearity

of

v(H) dependence

Dependences of domain wall velocity versus applied magnetic field measured in magnetically bistable amorphous microwires (a) and distribution of local nucleation fields measured in the same samples (b)

0 30 60 90 1200

100

200

300

400

500

0 30 60 90 1200

600

1200

1800

Hn, A

/m

sample1

HN

HN

sample2

x, mm

(b)

10 20 30 40 50 60

0

2000

4000

6000

8000

10000

v(m

/s)

H(A/m)

Ht=0(b)

H<HN

H>HN

Role of

defects

for

H>HN(J. Appl. Phys., 106 (2009) 103902

, )

- Magnetization direction

- DW propagation directionHext

dw1 dw2 dw3

pick-upcoil 1

(cd) (rd)

pick-upcoil 2

defectposition

macroscopic defectM

/Ms

11

-1

wire’s

axis

HN is

lower

at

the

ends

100 200 300 400 500 600

400

800

1200

92 A/m

V (m

/s)

H (A/m)

V(1-2) V(2-3)[m/s]

HN1=574 A/m

HN2=447 A/m

(a)

100 200 300 400400

800

1200

108 A/m

V (m

/s)

H ( A/m)

V(1-2) V(2-3)[m/s]

HN1=340 A/m

HN2=342 A/m

(b)

Typical v(H) dependences measured in different samples of magnetically bistable amorphous Fe74

B13

Si11

C2

microwires exhibiting (a) uniform and (b) accelerated DW propagation.

0 50 100 150 200-1000

-500

0

500

1000

1500

Hn( A

/m)

l (mm)

(a) 1 2 3

0 50 100 150 200-1000

-500

0

500

1000

1500

Hn (

A/m

)

l (mm)

(b) 1 2 3

Typical distributions of the local nucleation fields measured in the same Fe74

B13

Si11

C2

microwires for (a) uniform and (b) accelerated domain wall propagation. 1, 2 and 3 are the position of the pick-up coils.

100 200 300 400

400800

1200160020002400

0 50 100 150-1000

-500

0

500

1000

1500

V(m

/c)

H (A/m)

V(1-2) V(2-3)[m/s]

230 A/m

245 A/m

H=168A/m

l=52mm;Hn=168A/mHn (A

/m)

l(mm)

1 2 3

Correlation of local nucleation fields distribution (a) and V(H) dependences in magnetically bistable amorphous Fe74

B13

Si11

C2

microwire exhibiting accelerated domain wall propagation, 1, 2, 3 are the positions of the pick-up coils

Comparison of domain wall velocity v in amorphous Fe72.75

Co2.25

B15

Si10 micrometric wire and planar nanowire.

14 16 18400

600

800

v(m

/s)

H(Oe)d≈2,8 μm

and total diameter D≈

9μm

=0,31

Measured

v(H) for

490nmx

20nm Permalloy

nanowire

G.S.D. Beach

et al. / J. Magn. Magn. Mater. 320 (2008) 1272–1281 (maximum

v ≈110 m/s at9 Oe)

5 10 15 20

500

1000

1500

2000

5 10 15 20

500

1000

1500

2000

=0,31

v(m

/s)

H(Oe)

=0,76

Elevated

ME energy?(Small

-ratio)

50 100 150 200 250 300 350

600

900

1200

1500

1800

v, m

/s

H, A/m

sample 1 sample 2

0 400 800 1200

500

1000

1500

2000

0 400 800 1200

500

1000

1500

2000

Fe16Co60Si13B11

v(m

/s)

H (A/m)

=0.39

Co41.7Fe36.4Si10.1B11.8

ME energyis

important

100 200 300 400

400800

1200160020002400

0 50 100 150-1000

-500

0

500

1000

1500

V(m

/c)

H (A/m)

V(1-2) V(2-3)[m/s]

230 A/m

245 A/m

H=168A/m

l=52mm;Hn=168A/mHn (A

/m)

l(mm)

1 2 3

Role of

defects

Conclusions•

DW propagation in wires

is quite fast (few km/s).

•

We observed correlation of DW dynamics with magnetoelastic energy.

•

Quite fast DW propagation (v till 2500 m/s

at H about 30 A/m) has been observed in low magnetostrictive Co56

Fe8

Ni10

Si11

B16microwires.

•

Applied and internal stresses result in decreasing of DW velocity.We assume that in order to achieve higher DW propagation velocity at

the same magnetic field and enhanced DW mobility special attention should be paid to decreasing of magnetoelastic

energy.

•

At elevated magnetic field the role of defect is quite impotant:a new domain

can be spontaneously

nucleated

in front

of

the

propagating

head-to-head

domain

wall.

Magnetic bistability M

H

L>Lcr

L<Lcr

M

H

H>Hs

M

H

H<Hs