[PPT] - III Electronic Transport & Organic Spin Electronics S i El t PowerPoint Presentation

SLIDE 1

III Electronic Transport & Organic S i El t i Spin Electronics

P. Stamenov
Introduction to transport devices –

‘…from junctions to transistors.’

Organic electronics –

g ‘…from small molecules to polymers.’

Andreev Reflection –

‘So what is the spin polarization? ’ ‘So, what is the spin polarization?...’

Fermiology –

‘Either I mistake your shape and making quite; Or else you are that shrewd and knavish sprite…’

Planned work-

‘ for the remainder of the programme ’ …for the remainder of the programme.

NISE Tasks 3, 4 – Organics, Organic Spin Transistor NISE Tasks 2, 8 – Interface Layers, New Materials NISE Review 7-ix-2012

SLIDE 2

Staff, Publications

Plamen Stamenov Lecturer
Franklyn Burke Postgrad (Graduated early 2011)
Huseyin Tokuc Postgrad

Huseyin Tokuc Postgrad

Simone Alborghetti Postgrad (from September 2011)

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SLIDE 3

Publications: (This strand only) — Stamenov, P. "Point Contact Andreev Reflection from Erbium: Andreev Reflection from Erbium: The Role of External Magnetic Field and the Sign of the Spin Polarization" from Erbium: The Role of External Magnetic Field and the Sign of the Spin Polarization Journal of Applied Physics 111, 7 (2012) Alborghetti S Coey J M D & Stamenov P "Dependence of charge carrier injection — Alborghetti, S., Coey, J.M.D. & Stamenov, P., Dependence of charge carrier injection

n the interface energy barrier in short-channel polymeric field effect transistors",

Applied Physics Letters, 100, 14 (2012) — Burke, F., Stamenov, P. & Coey, J.M.D., "Charge injection, transport and localization in rubrene", Synthetic Metals, 161, 7-8, pp. 563-569 (2011) — Kurt, H., Rode, K., Venkatesan, M., Stamenov, P. & Coey, J.M.D., "High spin polarization in epitaxial films of ferrimagnetic Mn3Ga", Physical Review B - Condensed Matter and Materials Physics, 83, 2 (2011) — Kurt, H., Rode, K., Venkatesan, M., Stamenov, P. & Coey, J.M.D., "Mn3-xGa (0≤x≤1): Multifunctional thin film materials for spintronics and magnetic recording", Physica Status Solidi (B) Basic Research, 248, 10, pp. 2338-2344 (2011) — Monzon, L.M.A., Burke, F. & Coey, J.M.D., "Optical, magnetic, electrochemical, and

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electrical properties of 8-hydroxyquinoline-based complexes with Al3+, Cr3+, Mn2+, Co2+, Ni2+, Cu2+, and Zn2+", Journal of Physical Chemistry C, 115, 18, pp. 9182-9192 (2011)

SLIDE 4

Publications: (continued…) — Stamenov, P. & Coey, J.M.D., "Fermi level spin polarization of polycrystalline thulium by point contact Andreev reflection spectroscopy", Journal of Applied Physics 109 7 (2011) Physics,109, 7 (2011) — Tokuc, H., Oguz, K., Burke, F. & Coey, J.M.D., "Magnetoresistance in CuPc based organic magnetic tunnel junctions" Journal of Physics: Conference Series based organic magnetic tunnel junctions , Journal of Physics: Conference Series, 303, 1 (2011) — Venkatesan, M., Tokuc, H., Burke, F., Szulczewski, G. & Coey, J.M.D., Venkatesan, M., Tokuc, H., Burke, F., Szulczewski, G. & Coey, J.M.D., "Magnetic properties of the Co/Alq3 interface", Journal of Applied Physics, 109, 7 (2011)

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SLIDE 5

Introduction

Junctions & Devices

Anomalous

Metallic Structures (Non GMR) Metal-Organic Contacts GMR and TMR Junctions

Magnetoresistance Structures (In-plane Anisotropy) Magnetic Field Effects & Large Area Junctions Electronic & Magnetic Response Spin Injection/Detection Spontaneous Hall Effect Structures & Sensors (Linear Response) Perpendicular Anisotropy & Low Barrier Height Junctions for Spin Injection Field & Current Driven Switching Point Contacts & Andreev Reflection Short Channel Transistors Switching Oscillatory & High Frequency Response

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Reflection High Frequency Response

SLIDE 6

Introduction

Ferromagnetic Ferromagnetic Light ?

Spin Spin P

Ferromagnetic Metal (Fe) ?

r

Ferromagnetic Ferromagnetic Metal (Fe) ?

r

Ferromagnetic Light ?

r

Heat ?

r

Pump Probe

Ferromagnetic Semiconductor Mn:GaAs, (Co:ZnO) ? Ferromagnetic Semiconductor Mn:GaAs, (Co:ZnO) ?

r

Magnetic Field ?

Spin Transmitting Spin Injector Spin Detector

( ) ( )

Media Spin Manipulator

Normal Metal (Al) ?

r

Semiconductor (Si) Electrostatic Gate ?

r

M-M Junction ?

r

Schottky Junction ?

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( )

r

Semimetal (C) ? External Magnetic Field ?

r

Tunnel Junction ?

SLIDE 7

Organics - Tools

Two different deposition tools have been employed for the production of organic

and metal/organic stacks

The ‘Shamrock’ sputtering/UHV e-beam evaporation system
The ‘Magnolia’ UHV thermal evaporator with integrated low angle argon milling

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SLIDE 8

Organics - Rubrene

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SLIDE 9

Organics - Rubrene

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SLIDE 10

Organics Rubrene B2B Schottky

7.5x10

10

T = 300 K I** = 150 A/cm

2K 2 20 3

1.5x10

7
6

0.0 2.5x10

10

5.0x10

10

Nd = 1.10

20 m

3

Vbi = 10 mV Rs = 0.1*10

7 

1 = 0.215 eV 2 = 0.213 eV 1 = 8.466 nm 2 = 5.872 nm

1 903 T = 200 K I** = 60 A/cm

2K 2

Nd = 1e20 m

3

ent (A)

0.0 5.0x10

8

1.0x10

7
8
Exp. Data

Fits I /1 A) 300 K

5.0x10
10
2.5x10
10

1 = 1.903 2 = 2.596

Vbi = 10 mV Rs = 2*10

7 

1 = 0.223 eV 2 = 0.233 eV 1 = 9.289 nm 2 = 8.603 nm 1 = 5.532

Curre

1.0x10
7
5.0x10
8
10

200 K log(I

2
1

1 2

7.5x10
10

2 = 0.987

Applied Bias (V)

1.5x10
7
2
1

1 2

12

Applied Bias (V)

1 0 10

7

1.5x10

7

Rubrene NiFe A79 273 nm Dec

0.0 5.0x10

8

1.0x10

7

(A) creasing T

1.0x10
7
5.0x10
8

I (

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2
1

1 2

1.5x10
7

U (V)

SLIDE 11

Rubrene - WLMR

2.0x10

12

1.5x10

12

Data Fit Residue Rubrene/NiFe A80 T 10 K 5 0x10

13

1.0x10

12

T = 10 K L0 = 0.6 a0 L1 = 136 nm L2 = 66 nm

ctance (S)

0.0 5.0x10

2

ed Conduc

12

5.0x10
13

Detrende

15 10 5 5 10 15

1.5x10
12
1.0x10
12
15
10
5

5 10 15

Magnetic Field (T)

2D Weak Delocalisation model has been used to fit the data (T = 3 K) and

t t th diff t l li ti l th l t (136 ) lik l

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extract three different localisation scales – the longest one (136 nm) likely due to spin scattering

The effect vanishes very quickly and is unobservable above about 20 K

SLIDE 12

Organics - Rubrene

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SLIDE 13

Organics – P3HT

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SLIDE 14

Organics – P3HT

Organic film SAM

a) b)

NiFe

A Source Drain SiO2

NiFe

n++ silicon Gate

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SLIDE 15

Organics – P3HT & Alq3

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SLIDE 16

Organics – Alq3 & Pentacene

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SLIDE 17

PCAR Basics

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Taken from: Soulen R. J. et. al. Science 282 85 (1998)

SLIDE 18

PCAR Hardware

1.8 K < T <400 K, 0 < B < 1 T
Micromechanical & Piezo motion

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Thin films and Single crystals
Fast – > 1 spectrum per second

SLIDE 19

Setup and Some Important Considerations 1 Considerations 1

Micro- mechanical pushrod Superconductin g tip Contact terminals Sample support Piezo drive

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High Voltage insulation

SLIDE 20

Setup and Some Important Considerations 2 Considerations 2

Sample layer(s) layer(s) Substrate

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chip

SLIDE 21

Andreev Reflection and Textbook Materials Textbook Materials

2 0

No Fermi

1.8 2.0

Co / Nb T = 3.00(5) K

T * = 3.0(8) K 1* = 1.45(5) meV 2 = 1.5(2) meV

Z * 0 39(9) Ni / Nb T = 2.50(5) K

T * = 3.5(8) K 1* = 1.40(5) meV 2 = 1.5(2) meV

Z *= 0 26(9) Fe / Nb T = 6.80(5) K

T * = 1.7(8) K 1* = 1.19(2) meV 2 = 1.5(2) meV

Z *= 0 21(9) Cu / Nb T = 4.20(5) K

T * = 0.0(8) K 1* = 1.26(1) meV 2 = 1.5(2) meV

Z * 0 00(1)

10

No Fermi level polarisation

1.4 1.6

Z *= 0.39(9) P * = 0.42(9) Z *= 0.26(9) P * = 0.45(9) Z *= 0.21(9) P * = 0.45(3) Z *= 0.00(1) P * = 0.00(1)

30 20

Close to 50 % polarisation

1.0 1.2

G /GN

50 40

Pc (%)

Close to half-metallic l i ti

0.6 0.8

CuCrSeBr / Nb CrO2 Data CrO2 Fit Cu Data Cu Fit Fe Data Fe Fit

G

CrO / Nb

70 60

P

polarisation Degenerate semicond

0.2 0.4

CuCrSeBr / Nb T = 3.00(5) K

T * = 0.95(5) K 1* = 1.378(4) meV 2 = 1.5(2) meV

Z *= 0.43(2) P * = 0.40(1) Ni Data Ni Fit Co Data Co Fit CCSB Data CCSB Fit CrO2 / Nb T = 2.60(5) K

T * = 2.9(8) K 1* = 1.32(5) meV 2 = 1.5(2) meV

Z *= 0.42(8) P * = 0.86(9)

90 80

semicond. work too! Rough

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6
5
4
3
2
1

1 2 3 4 5 6 0.0

Applied Bias ()

100

Rough polarisation magnitude

SLIDE 22

PCAR - Tm

1.1

0.50

1.0

0.25 P

0.9 T = 2.2 K Gn = 35.5(5) G0

T * = 3.3(8) K 1* = 1.26(5) meV 

1 50 V G/Gn

0.00 0 5 1.0

8
4

4 8 0.8

Exp. Data

Fit

2 = 1.50 meV

Z *= 0.39(8) P * = 0.41(9)

1 2 3 4 5 6 7 8 9 10 0.0 0.5 Z

U (mV)

T (K)

1.0 1.2

No

0.6 0.8

1(0)

rature (K)

rmalized cond

0.2 0.4

Exp. Data

BCS fit

1(0) = 1.249(8) meV

T = 10 2 K

1/

Temper ductance G/G MAGNETISM & SPIN ELECTRONICS

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0.0 0.2 0.4 0.6 0.8 1.0 1.2 0.0 Tc 10.2 K T / Tc

Applied Bias (mV) Gn

SLIDE 23

PCAR - Er

370

0H(T), (deg) 1.015

Exp. Data

Fit

350 360

0, 0 1, 0 1, 90 1, 180 ce (G0)

1.000 1.005 1.010

T = 2.6 K Gn = 400(1) G0

2 = 1.50 meV

330 340

Conductanc

0.985 0.990 0.995

Contact 1

T * = 5.5(9)K 1* = 1.01(9) meV

Contact 2

T * = 6.4(9)K 1* = 1.01(9) meV

G /Gn

9
6
3

3 6 9 320 330

Applied Bias (2)

8
6
4
2

2 4 6 8 0.975 0.980

1

( ) Z *= 0.55(9) P * = 0.37(9)

1

( ) Z *= 0.81(9) P * = 0.44(9) Applied Bias U, mV pp

1.05 1.10

erature (K) G /Gn

0.95 1.00

Exp. Data

Fit T = 2.3 K

T * = 4 8(5)K

G /Gn

Tempe

0.85 0.90

T 4.8(5)K 1* = 1.46(1) meV 2 = 1.50 meV

Z *= 0.029(5) P * = 0.58(2) Gn = 134(5) G0

Applied Bias (mV)

Field (T) G /G0 mV

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15
10
5

5 10 15 0.80

n

Applied Bias U, mV Applied Bias (mV)

SLIDE 24

Mn2Ga – single capped layer

1 010 1.008 1.010

Exp. Data

Fit T = 2 4 K

1.02 1.04 1.004 1.006

T = 2.4 K

T * = 4.1(8) K 1* = 0.84(6) meV 2 = 1.50 meV

Z *= 0.29(5) P * 0 00(5) dI/dV

0.98 1.00

Exp. Data

Fit T = 2.2 K

T *

2 3(8) K dI/dV

1.000 1.002

P * = 0.00(5)

0.94 0.96

T * = 2.3(8) K 1* = 1.25(6) meV 2 = 1.50 meV

Z *= 0.59(7) P * = 0.4(1)

0.008
0.006
0.004
0.002

0.000 0.002 0.004 0.006 0.008

U (V)

0.010
0.005

0.000 0.005 0.010 0.92

U (V)

Initially an almost vanishing spin polarisation – the very few nm Typical bulk ferromagnetic metal spin polarisation of around 40

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p y are not polarized... spin polarisation of around 40 %, despite the large interfacial barrier

SLIDE 25

Mn2Ga – 1’ Temperature Scan

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SLIDE 26

Mn3Ga – single capped layers

1 75 2.00

Exp. Data

Fit

1 75 2.00

Exp. Data

Fit

1.25 1.50 1.75

Fit

1.25 1.50 1.75

Fit

0 50 0.75 1.00

Mn3Ga - 343 Gn = 292(3) G0 T = 2.1 K

T * = 2.4(8) K

G /Gn

0 50 0.75 1.00

Mn3Ga - 345a Gn = 443(3) G0 T = 2.2 K

T * = 1.3(8) K

G /Gn

5 0
2 5

0 0 2 5 5 0 0.00 0.25 0.50 T 2.4(8) K 1* = 1.086(3) meV 2 = 1.5 meV

Z *= 0.15(3) P * = 0.45(1)

5 0
2 5

0 0 2 5 5 0 0.00 0.25 0.50 1* = 1.38(2) meV 2 = 1.5 meV

Z *= 0.35(1) P * = 0.548(7)

5.0 2.5 0.0 2.5 5.0

Applied Bias (2)

5.0 2.5 0.0 2.5 5.0

Applied Bias (2)

Typical ferromagnetic spin polarisation of about 45 %, in a non-optimized sample Significant improvement of the spin polarisation after

ptimisation of growth

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p p p g parameters > 55 %

SLIDE 27

PCAR

An Example of a Novel Material Mn Ga An Example of a Novel Material – Mn3Ga

1.004 1.000 1.005 0.998 1.000 1.002 0.990 0.995

Exp. Data

Fit T = 2.1 K

T *

2 4(8) K G / GN

0 992 0.994 0.996

Exp. Data

Fit T = 2.2 K

T *

1 3(8) K dI/dV

0.985

T * = 2.4(8) K 1* = 1.086(3) meV 2 = 1.5 meV

Z *= 0.15(3) P * = 0.45(1)

0.988 0.990 0.992

T * = 1.3(8) K 1* = 1.38(2) meV 2 = 1.5 meV

Z *= 0.35(1) P * = 0.548(7)

6
4
2

2 4 6 0.980

Applied Bias (mV)

0.008
0.006
0.004
0.002

0.000 0.002 0.004 0.006 0.008 0.986

U (V)

C ld b k did t t i l f di l l i

Could become an key candidate material for perpendicular polarizers
Significantly different contacts can be formed on the same material
The maximal polarisation observed is relatively high ~ 55 % (higher than CoFe)
Going to position where PCAR is going to be the first not the last measurement

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Going to position where PCAR is going to be the first, not the last measurement

performed on a newly designed and synthesized material.

SLIDE 28

Mn3Ga – bi-layer punch through

1.010

Exp. Data

Fit T 2 6 K

1.010 1.012

Exp. Data

Fit

1.006 1.008

T = 2.6 K

T * = 6.9(8) K 1* = 0.716(9) meV 2 = 1.5(2) meV

Z *= 0.36(9) P * = 0.06(9) G = 317 G /dV

1.004 1.006 1.008

T = 2.4 K

T * = 0.1(5) K 1* = 0.647(9) meV 2 = 1.5(2) meV

Z *= 0.33(2) P * = 0.18(5) G 122 G /dV

1.002 1.004

G = 317 G0 dI/

0 996 0.998 1.000 1.002

G = 122 G0 dI/

0.006
0.004
0.002

0.000 0.002 0.004 0.006 1.000

U (V)

0.006
0.004
0.002

0.000 0.002 0.004 0.006 0.996

U (V)

1 04 0.960 1.00 1.02 1.04

V

0.945 0.950 0.955

Exp. Data

Fit V

0.96 0.98

Exp. Data

Fit T = 2.3 K

T * = 0.7(3) K 1* = 1.287(4) meV 2 = 1.5(2) meV

dI/dV

0 925 0.930 0.935 0.940

Fit T = 2.3 K

T * = 2.7(8) K 1* = 1.380(9) meV 2 = 1.5(2) meV

Z *= 0.25(5) P * = 0.58(6) dI/dV

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0.008
0.006
0.004
0.002

0.000 0.002 0.004 0.006 0.008 0.94

2

( ) Z *= 0.387(5) P * = 0.351(4) G = 207 G0 U (V)

0.015
0.010
0.005

0.000 0.005 0.010 0.015 0.920 0.925

( ) G = 126 G0 U (V)

SLIDE 29

Can we do better by adding Ru? Mn GaRu Mn2GaRu

1.04 1.06 1.01 0.98 1.00 1.02

Exp. Data

0.99 1.00

Exp Data

0.92 0.94 0.96

Exp. Data

Fit T = 2.3 K

T * = 4.9(8) K 1* = 1.30(3) meV  = 1 50 meV

dI/dV

0.98

Exp. Data

Fit T = 1.9 K

T * = 5.7(5) K 1* = 1.4(1) meV

1 50 V dI/dV

0 86 0.88 0.90

2 = 1.50 meV

Z *= 0.42(2) P * = 0.41(1) Gn = 136(1) G0

0 96 0.97

2 = 1.50 meV

Z *= 0.1(2) P * = 0.58(5) Gn = 93.5(1) G0

0.010
0.005

0.000 0.005 0.010 0.86

U (V)

0.015
0.010
0.005

0.000 0.005 0.010 0.015 0.96

U (V)

There is a clear trend of increasing spin polarisation upon adding Ru

(~1-5 at. %) into the structure. The total magnetic moment, however decreases.

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This type of material begins to resemble closely a compensated

ferrimagnet with high spin polarisation – highly desirable for the free layer in STT oscillators.

SLIDE 30

Mn3Ge

1.015 1.01 1.000 1.005 1.010 0.99 1.00

E D t

0.985 0.990 0.995

Exp. Data

Fit T = 2.6 K

T * = 5.0(9)K 1* = 1.0(2) meV 2 = 1.50 meV

G /Gn

0.96 0.97 0.98

Exp. Data

Fit T = 2.5 K

T * = 4.0(7)K 1* = 1.17(7) meV 2 = 1.50 meV

G /Gn

8
6
4
2

2 4 6 8 0.970 0.975 0.980

2

Z *= 0.5(2) P * = 0.4(1) Gn = 62.5(1) G0

10
5

5 10 0.94 0.95 0.96

2

Z *= 0.40(3) P * = 0.401(8) Gn = 124.5(1) G0

1.00 1.02

U (mV) U (V)

1.005 1.010 0.96 0.98

Exp. Data

Fit T = 2 0 K /Gn

0.990 0.995 1.000

Exp. Data

Fit /Gn

0.90 0.92 0.94

T 2.0 K

T * = 5.5(4)K 1* = 1.28(6) meV 2 = 1.50 meV

Z *= 0.36(3) P * = 0.46(2) G /

0 975 0.980 0.985 0.990

T = 2.2 K

T * = 6.4(9)K 1* = 0.7(4) meV 2 = 1.50 meV

Z *= 0.5(2) P * = 0 1(5) G /

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10
5

5 10 0.88

Gn = 158(1) G0 U (mV)

10
5

5 10 0.970 0.975

P = 0.1(5) Gn = 285.0(1) G0 U (V)

SLIDE 31

PCAR

O th P bi f B i d L C /Al Nb On the Probing of Buried Layers – Co/Alq3 - Nb

1 002 1 015 0.999 1.000 1.001 1.002

Exp. Data

Fit /dV

0.995 1.000 1.005 1.010 1.015

Exp. Data

/dV

0.005 -0.004 -0.003 -0.002 -0.001

0.000 0.001 0.002 0.003 0.004 0.005 0.995 0.996 0.997 0.998

Fit T = 2.4 K

T *= 0.6(5) K 1* = 1.5(4) meV 2 = 1.5(2) meV

Z *= 0.17(2) P * = 0.46(2) dI/

0.008
0.006
0.004
0.002

0.000 0.002 0.004 0.006 0.008 0.975 0.980 0.985 0.990

Fit T = 2.3 K

T *= -1.5(8) K 1* = 0.79(2) meV 2 = 1.5(2) meV

Z *= 0.08(3) P * = 0.39(3) dI/

Contact Quench

U (V) U (V)

SiO2/Co(10) - Nb SiO2/Co(10)/LiF(5) - Nb

1.000 1.002 1.004 0.995 1.000 1.005 0 994 0.996 0.998

Exp. Data

Fit T = 2.4 K

T *= 3.6(8) K 1 = 0.720(9) meV 2 = 1.5(2) meV

Z *= 0.10(8) P * = 0.50(7) dI/dV

0 975 0.980 0.985 0.990

Exp. Data

Fit T = 2.4 K

T *= 2.1(8) K 1* = 1.294(9) meV 2 = 1.5(2) meV

Z *= 0.40(2) P * = 0.40(2) dI/dV

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0.008
0.006
0.004
0.002

0.000 0.002 0.004 0.006 0.008 0.994

U (V)

0.015
0.010
0.005

0.000 0.005 0.010 0.015 0.975

U (V)

SiO2/Co(10)/Alq3(10)/LiF(5) - Nb SiO2/Co(10)/Alq3(30)/LiF(5) - Nb

SLIDE 32

M-S Junctions

On the Probing of Buried Layers – Co/Alq3 - Nb On the Probing of Buried Layers Co/Alq3 Nb

1 002 1 015 0.999 1.000 1.001 1.002

Exp. Data

Fit /dV

0.995 1.000 1.005 1.010 1.015

Exp. Data

/dV

1.001 1.002 1.010 1.015 1.000 1.005 1 002 1.004

0.005 -0.004 -0.003 -0.002 -0.001

0.000 0.001 0.002 0.003 0.004 0.005 0.995 0.996 0.997 0.998

Fit T = 2.4 K T *= 0.6(5) K 1* = 1.5(4) meV 2 = 1.5(2) meV Z *= 0.17(2) P * = 0.46(2) dI/

0.008
0.006
0.004
0.002

0.000 0.002 0.004 0.006 0.008 0.975 0.980 0.985 0.990

Fit T = 2.3 K

T *= -1.5(8) K 1* = 0.79(2) meV 2 = 1.5(2) meV

Z *= 0.08(3) P * = 0.39(3) dI/

Contact Quench

0.999 1.000 1.000 1.005 0.995

E D

1.000 1.002

U (V) U (V)

0.997 0.998

Exp. Data

Fit T = 2.4 K

T *= 0.6(5) K  * = 1 5(4) meV

dI/dV

0.990 0.995

Exp. Data

Fit T = 2.3 K

T *= -1.5(8) K

dI/dV

0.985 0.990

Exp. Data

Fit T = 2.4 K

T *= 2.1(8) K 1* = 1.294(9) meV

dI/dV

0.998

Exp. Data

Fit T = 2.4 K

T *= 3.6(8) K  = 0.720(9) meV

dI/dV

1.000 1.002 1.004 0.995 1.000 1.005

0 995 0.996

1 = 1.5(4) meV 2 = 1.5(2) meV

Z *= 0.17(2) P * = 0.46(2)

0.980 0.985

1* = 0.79(2) meV 2 = 1.5(2) meV

Z *= 0.08(3) P * = 0.39(3)

Contact Quench

0.975 0.980

1

( )

2 = 1.5(2) meV

Z *= 0.40(2) P * = 0.40(2)

0 994 0.996

1

0.720(9) meV

2 = 1.5(2) meV

Z *= 0.10(8) P * = 0.50(7)

0 994 0.996 0.998

Exp. Data

Fit T = 2.4 K

T *= 3.6(8) K 1 = 0.720(9) meV 2 = 1.5(2) meV

Z *= 0.10(8) P * = 0.50(7) dI/dV

0 975 0.980 0.985 0.990

Exp. Data

Fit T = 2.4 K

T *= 2.1(8) K 1* = 1.294(9) meV 2 = 1.5(2) meV

Z *= 0.40(2) P * = 0.40(2) dI/dV

0.005 -0.004 -0.003 -0.002 -0.001

0.000 0.001 0.002 0.003 0.004 0.005 0.995

U (V)

0.008
0.006
0.004
0.002

0.000 0.002 0.004 0.006 0.008 0.975

U (V)

0.015
0.010
0.005

0.000 0.005 0.010 0.015 0.975

U (V)

0.008
0.006
0.004
0.002

0.000 0.002 0.004 0.006 0.008 0.994

U (V) MAGNETISM & SPIN ELECTRONICS

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With an additional thick layer of small molecule organic on top – a wide proximity region is observed with a rather low superconducting gap value.

0.008
0.006
0.004
0.002

0.000 0.002 0.004 0.006 0.008 0.994

U (V)

0.015
0.010
0.005

0.000 0.005 0.010 0.015 0.975

U (V)

When only Co/(Co1+xO1-x?) is present – there is almost no proximity region and spin polarisation is preserved at the bulk value. With LiF cap on top – the microscopic structure of the contact is different, with likely broken down contact area – critical current is exceeded at a low bias With an additional thin layer of small molecule organic on top – the spin polarisation of the metal is preserved, though within a very diffused contact.

SLIDE 33

Co/LiF

An example of cold electrons 1

1.06

An example of cold electrons 1

1.02 1.04 0.98 1.00

Exp. Data

Fit dI/dV

0.96 0 98

Fit T = 2.3 K

T *= -0.3(8) K 1* = 1.3(2) meV

d

0.010 -0.008 -0.006 -0.004 -0.002

0.000 0.002 0.004 0.006 0.008 0.010 0.92 0.94

2 = 1.5(2) meV

Z *= 0.04(3) P * = 0.35(3) U (V)

Note the negative electronic temperature offset. Energy filtering filterring

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g p gy g g using thin superconducting layers should be possible (at least at low temperatures).

SLIDE 34

Co/LiF

An example of hot electrons

1.030

Exp. Data

An example of hot electrons

1.020 1.025

Exp. Data

Fit T = 2.3 K

T *= 7.7(8) K  * = 0 83(4) meV

1.015

1 = 0.83(4) meV 2 = 1.5(2) meV

Z *= 0.04(9) P * = 0 32(2) dV

1.005 1.010

P 0.32(2) dI/d

1.000

0.020
0.015
0.010
0.005

0.000 0.005 0.010 0.015 0.020 0.995

U (V)

MAGNETISM & SPIN ELECTRONICS

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Actually, the common case is the opposite – the electrons are usually hotter than the lattice (at least in terms of effective thermal distribution).

SLIDE 35

Co/Alq3/LiF

An example of cold electrons 2

1 012 1.014

Exp. Data

Fit

An example of cold electrons 2

1 004 1.005 1 006 1.008 1.010 1.012

Fit T = 2.4 K

T *= -0.4(8) K 1* = 1.20(2) meV 2 = 1.5(2) meV

1.002 1.003 1.004 1 000 1.002 1.004 1.006

Z *= 0.46(3) P * = 0.03(3) dI/dV

0.999 1.000 1.001

Exp. Data

Fit T = 2.5 K dI/dV

0 994 0.996 0.998 1.000 0 996 0.997 0.998

T *= -1.0(8) K 1* = 1.42(2) meV 2 = 1.5(2) meV

Z *= 0.07(3) P * = 0 31(3)

0.008
0.006
0.004
0.002

0.000 0.002 0.004 0.006 0.008 0.994

U (V)

There is certain resemblance with

0.006
0.004
0.002

0.000 0.002 0.004 0.006 0.996

P = 0.31(3) U (V)

It is not necessary, however, to lose There is certain resemblance with Mossbauer spectra - the more components there are - the worse is the signal-to-noise ratio! Three It is not necessary, however, to lose all spin polarisation! The ‘unquenched’ part of the contact can exhibit Andreev reflection

MAGNETISM & SPIN ELECTRONICS

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the signal-to-noise ratio! Three components - is a practical limit. exhibit Andreev reflection suppression just as well...

SLIDE 36

Co/Rubrene, Znq2(10,30)/LiF

An example An example

1.00 1.01 1.02 1.04 1.06 0.97 0.98 0.99

Exp. Data

Fit T = 2.4 K

T * = 3.1(8) K 1* = 1.14(1) meV

G / Gn

0.94 0.96 0.98 1.00

Exp. Data

Fit T = 2.4 K

T * = 3.1(8) K

G / Gn

0.008
0.006
0.004
0.002

0.000 0.002 0.004 0.006 0.008 0.94 0.95 0.96

1

( )

2 = 1.50 meV

Z *= 0.38(2) P * = 0.36(2) Gn = 37.5(1)

0.84 0.86 0.88 0.90 0.92

1* = 1.16(2) meV 2 = 1.50 meV

Z *= 0.40(2) P * = 0.40(6) Gn = 108.0(1) U (V)

0.995 1.000 1.005

0.020
0.015
0.010
0.005

0.000 0.005 0.010 0.015 0.020

U (V)

1.005 0.980 0.985 0.990 0.995

Exp. Data

Fit T = 2.4 K

T * = 3.1(8) K 1* = 1.20(3) meV

1 V G / Gn

0.995 1.000

Exp. Data

Fit T = 2.4 K

T * = 3.1(8) K 1* = 1.20(3) meV

G / Gn

0.010 -0.008 -0.006 -0.004 -0.002

0.000 0.002 0.004 0.006 0.008 0.010 0.965 0.970 0.975

2 = 1.50 meV

Z *= 0.42(2) P * = 0.35(2) Gn = 55.4(1) U (V)

0.008
0.006
0.004
0.002

0.000 0.002 0.004 0.006 0.008 0.990

1

0(3) e

2 = 1.50 meV

Z *= 0.35(5) P * = 0.38(5) Gn = 184.5(1)

MAGNETISM & SPIN ELECTRONICS

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Cobalt is still cobalt even when it is just 10 nm thick and buried under Rubrene or Znq2... Close-to-bulk spin polarisation is still measurable.

U (V) U (V)

SLIDE 37

PCAR-HOPG (low-SO semimetal)

1.4 1.01 0.8 1.0 1.2

Exp. Data

1.00

Exp. Data

0.4 0.6

p Fit T = 2.4 K

T * = 3.5(9)K 1* = 1.1(9) meV 2 = 1.50 meV

Z *= 0.87(9) G /Gn

0.98 0.99

Fit T = 2.0 K

T * = 2.1(3)K 1* = 1.09(5) meV 2 = 1.50 meV

Z *= 1.0(1) G /Gn

8
6
4
2

2 4 6 8 0.0 0.2

P * = 0.2(2) Gn = 0.40(1) G0 Ua (mV)

8
6
4
2

2 4 6 8 0.97

P * = 0.0(2) Gn = 372.0(1) G0 Ua (mV)

0.90 0.95 1.00

0H (T)

0.0 0.1 0.2 0.3 0.4 0.5 0 6 G /Gn 0.94

30
20
10

10 20 30 0.75 0.80 0.85 0.6 0.7 0.8 0.9 1.0 G T = 2.1 K Gn = 338.99(2) G0 @ (0 mV, 15 K) c

0H

HOPG ZYA Nb 0 88 0.90 0.92

Exp. Data

Fit Gn = 335.9(1) G0 T = 3.3 K

30
20
10

10 20 30 Ua (mV)

re (K)

0.84 0.86 0.88

Contact 2

T * = 4.6(9)K 1* = 1.1(9) meV 2 = 1.50 meV

Contact 1

T * = 1.6(9)K 1* = 0.34(9) meV 2 = 1.50 meV

G /Gn

Temperatur G /Gn

MAGNETISM & SPIN ELECTRONICS

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NISE Midterm Review

15
10
5

5 10 15 0.80 0.82

2

Z *= 0.16(9) P * = 0.0(1)

2

Z *= 0.49(9) P * = 0.0(1) Ua (mV)

Applied Bias (mV)

SLIDE 38

PCAR - HOPG

35 40

slope = 30.2(2) k q

1

2

1.5

20 25 30 35 mV)

slope 30.2(2) kBq

1 mV)

1.8
1.7
1.6

A

5 10 15 w (m

w = 4.2(5) mV + 2.60(9) mVK

1 T
1

x0 (m <x0> = 0.15(3) mV

8.0 8.5 w (mV)

2.0
2.5
2

1.2

7.5 0.96

1.0
1.5

A

Tc = 10.2 K T (bulk Nb) = 9.2 K

1.1 y0

0.92 0.94 1 40 1.42 y0

2 4 6 8 10 12 0.0

0.5

T (K)

c(

) A (0 K) = 2.55

2 4 6 8 10 12 1.0 <y0> = 1.152(2) T (K)

1.32 1.34 1.36 1.38 1.40



T (K) T (K)

0.0 0.2 0.4 0.6 0.8 1.0

0H (T)

Magnetic field The temperature dependencies of the spectral widths and amplitudes are quite unexpected only

MAGNETISM & SPIN ELECTRONICS

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NISE Midterm Review

g dependencies of the spectral parameters comparable to ones observed in artificial double magnetic tunnel junction structures.

SLIDE 39

9 1 6 9 1 8

PCAR-Bismuth (high-SO semimetal)

1.16

Exp Data

850

9 1 0 9 1 2 9 1 4 9 1 6

1.08 1.12

Exp. Data

Fit T = 2.2 K

T * = 3.7(9)K 1* = 0.8(4) meV 2 = 1.50 meV

Z *= 0.4(5)

830 835 840 845

G (G0)

9 0 2 9 0 4 9 0 6 9 0 8

G (G

0)

1.00 1.04

Z 0.4(5) P * = 0.09(7) Gn = 452.0(1) G0 G /Gn

6
4
2

2 4 6 820 825

U (mV)

3 0
2 0
1 0

1 0 2 0 3 0 8 9 8 9 0 0 9 0 2

U ( m V )

10
5

5 10 0.96

Ua (mV)

K) mperature (K G /Gn Tem

MAGNETISM & SPIN ELECTRONICS

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NISE Midterm Review Applied Bias (mV)

SLIDE 40

PCAR

Conclusions and Outlook Conclusions and Outlook

Information about the spin polarisation, proximity gap and

electronic heating & cooling can be reliably extracted electronic heating & cooling can be reliably extracted

Future work on the introduction of high magnetic fields (up to 14

g g ( p T) and the extraction of the sigh of spin polarisation despite the large s-o coupling

Further work on SQUID based current detection for better

signal-to-noise ratios

Future work on the introduction of coherent RF radiation and the

use of Shapiro steps for absolute energy calibration use of Shapiro steps for absolute energy calibration

Future work on piezo-strained substrates and gating for direct

MAGNETISM & SPIN ELECTRONICS

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control over the Fermi level All development to work under a current SFI - SIRG

SLIDE 41

SrRuO3/SRO – a ‘bad’ metal

6.0x10

8

5.0x10

8

5.5x10

8

m m_fit

4.5x10

8

mz(Am

2)

2 4 6 8 10 12 14 16 3.5x10

8

4.0x10

8

m0H (T)

0 4 0.5

ZFC FC in 10mT

1.10 1.15

0.3 0.4

B/Ru)

0.95 1.00 1.05

Exp. Data

Fit T = 2 2 K Gn

0.1 0.2

M (B

Tc = 150K

0.80 0.85 0.90 T = 2.2 K

T * = 5.7(3)K 1* = 1.47(6) meV 2 = 1.50 meV

Z *= 0.1(1) P * 0 56(6) G /G

MAGNETISM & SPIN ELECTRONICS

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NISE Midterm Review

80 100 120 140 160 180 200 0.0

T(K)

c

10
5

5 10 0.70 0.75 P * = 0.56(6) Gn = 113.0(1) G0 U (mV)

SLIDE 42

SRO/STO – Non-oscillatory MR

12 300 K 10 11 m) Data Fit 300 K 8 9 150 K 160 K 175 K 200 K

xx (.c

6 7 140 K 150 K 80 120 160 140 K 150 K 160 K m) 40 80 175 K 200 K 300 K

xy (n.cm

D t

120
80
40



Data Fit

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NISE Midterm Review

2 4 6 8 10 12 14 120

0H (T)

SLIDE 43

SRO/STO – Below TC

0.03

20

0.01 0.02

T = 140 K T = 130 K )

20

R

sat xy (m)

0.01

0.00

T = 120 K T = 115 K Rxy (

40
1

R

x

T)

2
1

1 2

0.03
0.02

0H (T)

Way Down Way Up T = 7 K

4
3
2

R

slope xy

(/mT

0.04 0.05

T (K) 7

4 100 150 200 R mT)

0.02 0.03

Ryy () Way Down Way Up 7 115 120 130 140

20 40 60 80 100 120 140 160 50 100

0Hc (m

0 00 0.01

20 40 60 80 100 120 140 160 T (K)

The detailed carrier normal scattering

ffi i t b i ibl b l T

MAGNETISM & SPIN ELECTRONICS

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NISE Midterm Review

2
1

1 2 0.00

0H (T)

coefficients become inaccessible below TC.

The spontaneous scattering and the

majority carrier normal ones are accessible.

SLIDE 44

SRO/STO – Fermi surface and Magnetic Anisotropy

T = 300.0 K

Magnetic Anisotropy

T = 150.0 K T = 2.0 K XRD Phase Fraction: 0.465 (1/1.15) Apparent FS anisotropy: 0.64 (~1/2)

MAGNETISM & SPIN ELECTRONICS

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NISE Midterm Review

Apparent FS anisotropy: 0.64 ( 1/2) Deduced FS anisotropy: 0.82 (~1/4)

SLIDE 45

Conclusions

Devices based on small-molecule-organic single crystals will

require a different fabrication approach with particular attention on require a different fabrication approach, with particular attention on lowering the interfacial barriers.

Polymer based organic FETs are to still demonstrate any spin
Polymer-based organic FETs are to still demonstrate any spin
functionality. Transport mechanisms need to be investigated further

for various preparation conditions. The interface is critical p p

PCAR has good potential as an interface characterization

technique not only for the determination of Fermi surface spin technique, not only for the determination of Fermi surface spin polarization, but also spin diffusivity, superconducting proximity, etc

Detailed magnetotransport (even without ShdH) can be a really
Detailed magnetotransport (even without ShdH) can be a really

useful tool for electronic structure characterization, and in many cases it is complementary to bulk magnetometry.

NISE Midterm Review

p y g y

SLIDE 46

Future work Future work

Soft-metal in-vacuo bonding of organic microcrystals
Complete the spectrum of investigated organic materials

with a few further examples of small-molecule organics and polymers.

D

l hi h H d hi h T PCAR ( d SIRG)

Develop high-H and high-Tc PCAR (under SIRG)
Deploy well-characterized SRO, etc. in low-temperature

demonstrators devices and Ru:MnGa in prototype low I demonstrators devices, and Ru:MnGa in prototype low-Ic switching devices.

MAGNETISM & SPIN ELECTRONICS

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SLIDE 47

The TCD Magnetism Group (2012)

NISE Midterm Review