Manipulation of the magnetization of Perpendicular magnetized Rare-earth-transition ... ·...

Manipulation of the magnetization of Perpendicular magnetized

Rare-earth-transition metal alloys using polarized light

S. Mangin

Jan 31st 2013 IEEE – Magnetic Society

7th Framework Program for Research

IEF : Intra-European Fellowships

IOF : International Outgoing Fellowships

IIF : International Incoming Fellowships

IIF

IOF

IEF

Optical Probe and Manipulation of Magnetization at the nanometer scale


Nancy

Nancy

Nancy (France)


Born from 5 laboratories merging : 400 peoples Nano-science Surface science Nuclear Fusion Metallurgy

Jan 2015 : New common building

Institut Jean Lamour


http://www.lpm.u-nancy.fr/nanomag/

2 technicians, 2 CNRS researcher, 7 faculty members, 6 Ph.D & Post-Doc

…

Nanomagnetism /Spintronic


Magnetization & Spin manipulation

Magnetic Field Polarized Current

Light

Heat

Electric Field Strain

H

E

e-


Outlines

•  Introduction •  All optical switching •  Our goals

•  All optical switching for TbCo •  Influence of composition •  Influence of thickness

•  Devices •  How to record magnetization switching in TbCo


All optical switching

20 nm thick Gd22Fe74.6Co3.4

40 fs pulses, 1 kHz repetition

C.D. Stanciu et al, Phys. Rev. Lett. 99, 047601 (2007) Jan 31st 2013 IEEE – Magnetic Society

Light induced magnetization reversal

All-optical switching with circularly polarized light

Stanciu et al., PRL 99, 047601 (2007)

(40 fs single pulses)

GdFeCo

All-optical writing works without any applied external magnetic field All-optical writing event depends on combination magnetization and laser helicity All-optical switching only works above a certain fluence threshold

What is (are) the mechanism(s) ?

Light

Magnetic field created by a laser beam

Heat transfer by the laser

Angular momentum transfer by the laser

Still under discussion


Magnetic field

Could reach several Tesla ?

Short field pulse

From LLG equation 100 ps field pulse is needed LLB ?

Sign depends on polarization

-1.0-0.50.0

0.51.0

-1.0

-0.5

0.0

0.5

1.0

-1.0-0.50.00.51.0

mz

m ymx

HIFE ~ 0.52kOe J.M. Li et al J. Appl.Phys. 111, 07D506 (2012)


Heat

Radu et al., Nature 472, 205 (2011)

Ferrimagnetic material is needed

Will depend on pulse length

Doesn’t depends on polarization


Angular Momentum transfer

Sign depends on polarization

Light transfers little angular momentum


What are the Interactions / Time scales

Field switching

Spin Transfer

Slow

Fast


What are the important parameters ?

20 nm thick Gd22Fe74.6Co3.4 40 fs pulse 1 kHz repetition

Polarization ?

Pulse length ?

Fluence ?

Repetiton ?

Laser

Thickness ?

Rare earth – Transition metal ?

Ferrimagnetic ?

Composition ? Material


Why RE-TM alloys ?

ferrimagnetic RE-TM alloy

rare earth transition metal alloy (Gd, Tb) (Fe, Co ,Ni) (GdFeCo)


The materials : Ferrimagnetic alloys

M

MTb

MCo

TbXCo1-X

MRE= gRE (γ ) ARE

M

MTb M

MCo MCo

MTb

MTM= gTM (γ ) ATM

gRE = gTM

Angular Momentum Compensation at TA

Magnetization Compensation at TM Jan 31st 2013 IEEE – Magnetic Society

Can we use it ?

Phys Rev B 86, 140404(R) (2012)

Magnetic data storage, Magnetic Memories , Magnetic Logic ?

Low energy 10 fj to switch 20 nm x 20 nm

Fast Magnetizations reversal in 100 fs

High density ?

High Perpendicular Magnetic anisotropy

Detectable ?

Can a current “read” Magnetization orientation


Our Goal

Demonstrate AOS for other materials

Tune parameters

Better understanding

Find material compatible with application requirement

Build devices

Magnetization

Thickness


All-optical switching in TbCo AG Aeschlimann: circular polarized LASER beam, spot size: 20 µm

∼1 mm


AOS – TbCo vs GdCo

Tb0.26Co0.74 Ferrimagnetic HC = 6 000 Oe HK = 6 T Close to compensation

t= 20 nm 400 fs and 10ps All-optical switching for a high anisotropy material ( ~ 4x106 ergs/cm3)

Gd22Fe74.6Co3.4 Ferrimagnetic HC = 400 Oe Low HK Close to compensation t= 20 nm 50 fs

= =

=

=

=

=

=


Amorphous structure of Co1-xTbx alloys

Co1-xTbx (t nm)

Cu(2nm) /Pt(2nm) capping

substrate + Ta(5nm) buffer

25 nm

25 nm 0.25 0.50 0.75 1.00

0

50

100

150

dTb-Tb=3.52 Å

dCo-Tb=3.01 Å

dCo-Co=2.50 Å

I [a.

u.]

1/d [1/Å]

dC-C = 1.54 Å

Co74Tb26

Au

è Co1-xTbx amorphous for 12% ≤ x ≤ 26%

Transmission electron microscopy:


Perpendicular anisotropy

-6 -3 0 3 6-400

-200

0

200

400

M [k

A/m

]µ0H [T]

x =16% x =23%

-1 0 1-400

-200

0

200

400 x=16% x=23%

M [k

A/m

]

µ0H [T]

H

H

è Co1-xTbx has PMA for 8% ≤ x ≤ 34% Jan 31st 2013 IEEE – Magnetic Society

0.72 0.76 0.80 0.84 0.880

200

400

600 MS

M [k

A/m

]

T = 300 K

1-x

Tunable magnetization

0 50 100 150 200 250 3000

50

100

150

200

250

x = 20 %

M [k

A/m

]T [K] Tcomp= 280 K

è 0 ≤ M (x,T) ≤ 600 kA/m

m m │m│ = │mTb-mCo│ Tb

Tb

Co

Co

Tb

Co m

Co

Co

Tb Tb

m

m

m Tb

Co

M. Gottwald, et al J. Appl. Phys 111 083904 (2012)

Tunable Perpendicular Magnetic Anisotropy

50 100 150 200 250 300

x = 12 x = 16 x = 20 x = 23 x = 26

T [K]0.72 0.76 0.80 0.84 0.88

0.0

0.5

1.0

1.5

2.0

K [M

J/m

3 ]

1-x [at.%]

Ku Keff

T = 300 K

è Origin of PMA unclear è 50 kJ/m3 ≤ K (x,T) ≤ 1600 kJ/m3


15 20 25 300

300

600only

thermal effects

only thermal effects

TcompTCurie

T [K

]

xTb,vol[%]

all-optical

Composition influence on AOS

m Tb

Co

m Tb

Co

AOS observed close to compensation

Conclusion

AOS observed above compensation Jan 31st 2013 IEEE – Magnetic Society

Understanding

At TA any torque is very efficient




Not efficient

Bring the sample to TA

Switching at TA

Stanciu et al, Phys. Rev. B 73, 220402 (2006) Jan 31st 2013 IEEE – Magnetic Society

Influence of the composition


Influence of concentration and pulse duration

S. Alebrand et al., Appl. Phys. Lett. 101, 162408 (2012) Jan 31st 2013 IEEE – Magnetic Society

Thickness dependence

Competition between:

Heat transfer

Angular momentum transfer


Model




+


Data Storage

Memories

Logic Read Data

Applications


Transport measurements to Read

( )2

21

21⎟⎟

⎠

⎞

⎜⎜

⎝

⎛

⋅

⋅⋅=Δ

MMMMGMRMR

Anisotropic Magnetoresistance (AMR)

Extraordinary Hall Effect (EHE)

Giant Magnetoresistance (GMR)

M V+

V-

M2

M1 I

I

M

I θ

ΔR(M) = (R║ - R┴)cos2(θ)

( ) ( )IMeMIRMR z

EHE

⋅

⋅×⋅=Δ

è M ║ I

è M ┴ plane

è θ(M1,M2) Jan 31st 2013 IEEE – Magnetic Society

Transport properties of CoTb alloys

-0.8 -0.4 0.0 0.4 0.8

0.0

0.3

0.6

-1.0

-0.5

0.0

0.5

1.0

ΔR/R

[10−

3 ]

µ0H [T]

ρ H/ρ

[%

]

I I

UH

UH

U U

800 µm

200 µm

MgO/Co88Tb12/MgO

-0.8 -0.4 0.0 0.4 0.8

µ0H [T]

mH m

H m H

m m

H=0 H

èComplementary tools to observe magnetization reversal

1 2 3

1

1 2

2

3

3

1

1

1

2

2

2


Spin valves

-0.8 -0.4 0.0 0.4 0.8-0.02

-0.01

0.00

-0.5

0.0

0.5

-1

0

1

GM

R [%

]

µ0H [T]

ρ H/ρ

[%]

m [a

.u.]

Co74Tb26

è Decoupled soft & hard layer

è EHE Sign positive for Co sublattices

è GMR sign : Co sublattices

è Small GMR (low polarization, short electron mean-free path?)

Co88Tb12 800 µm

200 µm

m Tb Co

m Tb Co 1 2 3

1

2 3

1

2 3

1

2

3

M. Gottwald et al Phys. Rev. B 85, 064403 (2012)

C. Bellouard et al Phys. Rev. B 53, 5082-5085 (1996)


Conclusion

Demonstration of AOS for TbCo

Composition and thickness dependence

Model based on Heat + Angular momentum transfer

TbCo reversal may be probed using transport measurements

S. Alebrand et al., Appl. Phys. Lett. 101, 162408 (2012)

M. Gottwald et al Phys. Rev. B 85, 064403 (2012) M. Gottwald, et al J. Appl. Phys 111 083904 (2012)


Acknowledgments

Martin Aeschlimann Sabine Alebrand

Matthias Gottwald Eric E. Fullerton

Michel Hehn

Daniel Steil Mirko Cinchetti

Daniel Lacour


International French-USA Workshop Toward Low Power Spintronic Devices

July 8th - 12th , 2013 La Jolla, California

http://nanomag.ucsd.edu/iwst/ Contact information: Iris Villanueva

e-mail: [email protected]

A. FERT (Nobel Prize 2007): CNRS/ Thales (France) * S.S.P. PARKIN : Stanford / IBM –Almaden (USA)* H. OHNO: Tohoku University (Japan) * B. DIENY: Spintec (France) *

J. Z. SUN: IBM-Yorktown Height (USA) * J. A. KATINE: HGST-WD- San Jose (USA)* I. SCHULLER : UC San Diego (USA) * A. THIAVILLE: University Paris Sud (France) *

K. LEE: Qualcomm- San Diego (USA)* D. RALPH: Cornell University (USA) * A. HOFFMANN: Argonne National Laboratory (USA)* Y. SUZUKI: Ozaka University (Japan) T.ONO, Kyoto University (Japan)* V. LOMAKIN: UC San Diego (USA)*

Y. OTANI: University of Tokyo and RIKEN (Japan) * L. PREJBEANU : Crocus (France) L.VILA: INAC-CEA (France) * D. APALKOV: Samsung Electronics - Grandis (USA) *

D.L STEIN: New York University (USA)* J.ÅKERMAN: University of Gothenburg (Sweden)* *confirmed speakers

Abstracts (see template online) must be submitted before March 1, 2013. Posters and oral presentations will be selected by the scientific committee and authors will be informed of the selection by April 1st.

Registration will be accepted until June 1st

Manipulation of the magnetization of Perpendicular magnetized Rare-earth-transition ... ·...

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