x-ray absorption spectroscopy

MAX-PLANCK-UBC CENTRE FOR

QUANTUM MATERIALS

International Summer School on Surfaces

and Interfaces in Correlated Oxides

30th

August, 2011

Dipartimento di Fisica

Politecnico di Milano

Italy

Giacomo Ghiringhelli

[email protected]


Introducing myself...

2

Picture of POLIMI

Keywords:

• Synchrotron radiation

• Soft x-rays

• Resonant spectroscopy

• 3d transition metal oxides


Summary

3

1. Why synchrotron radiation?

• Main properties

• Absorption edges and x-ray energies

2. XAS: x-ray absorption spectroscopy

• Basic process and the choice of absorption edges

• XLD and XMCD: polarization dependent XAS

• Some examples on oxide interfaces

3. RIXS: resonant inelastic x-,ray scattering

• A second order process

• dd excitations

• Magnetic excitations


Synchrotron radiation, summary

4


Undulators: many photons

5


Undulators: polarization control

6

L u c e p o l a r i z z a t al i n e a r m e n t e

L u c e p o l a r i z z a t ac i r c o l a r m e n t e

E l e t t r o n i

E l e t t r o n i

C a m p o m a g n e t i c o

C a m p o m a g n e t i c o

Full control of the polarization at the source:

• Linear horizontal or vertical or any orientation (more difficult)

• Circular Right or Left handed


Beam line

7

High quality mirrors, gratings and crystals are needed to make the beam monochromatic (bandas narrow as possible)and to focalize it onto the sample

Parameter Typical figures

Flux at the sample 1010 - 1013 photons/s

Beam size at sample (hoz x ver) 50 m x 5 m - 1 mm x 1 mm

Energy bandpass: UV (20 – 50 eV)soft x rays (300 – 1000 eV)hard x rays (2 - 10 keV)

10 - 50 meV50 – 500 meV50 – 500 meV

State of the art beam lines for resonant spectroscopy


X-ray spectroscopy for 3d Transition Metal systems

8

X-ray resonant spectroscopies

• XAS: x-ray absorption

spectroscopy

• XLD and XMCD: polarization

dependent XAS

• RIXS: resonant inelastic x-ray

scattering

• Resonant reflectivity

• Resonant Elastic X-ray

Scattering

• Resonant Photoemission

E

EF

Ev

3dTM oxides

3p

2p

1s

4sp3d

Ox 2p


X-ray Absorption measurements

9

X rays

e

X rays

nA

Tunable or “white” source

Monochromator

Detection:

• transmission (only hard x-rays)

• fluorescence yield

• electron yield (including drain current)


X-ray Absorption Cross Section

10

0.0

0.5

1.0

1.5

2.0

2.5

10 100 1000 10000

1E-4

1E-3

0.01

0.1

1

Cu K

9000 eV

O K

530 eV

A

bso

rpti

on

co

eff

icie

nt

(arb

. u

.)

Photon Energy (eV)

CuOCu L

2,3

930-950 eV

log scale

Linear

scale

Cu

M edges


Resonances in the XAS

11

K edge 530 eV

3d

EFermi

E

3p

2p

1s

1s

2sM2,3 edges (28-77 eV)

L2,3 edges (400-950 eV)

K edge (4.5-9.0 keV)

2p

3d TM Oxygen4sp

2p

Rare Earths

L2,3 edges

(5.5-10 keV)

3dM4,5 edges

(830-1580 eV)

6s,5d

4f

Strong resonances


Core levels

12

0 10 20 30 40 50 60 70 80 90 100

10

100

1000

10000

100000

O

GG - Politecnico di Milano; Source: X-ray data booklet, Lawrence Berkeley National Laboratory 25/03/02 18:29:59

4d5/2

4p3/23d

5/23p

3/2

2p3/21s

Fe Mo Th

Actinides

AuLuGdCe

RE

CdYZnSc

4dTM3dTM

SiC

Hard

X-R

ay

sS

oft

X-R

ay

sU

V

Bin

din

g e

ner

gy

(eV

)

Atomic number Z

K

L3

M3

M5


3p: M2,3 edge XAS

13

Source: S. Nakai, et al PRB 9, 1870 (1974)

Spin-Orbitsplitting

Spin-Orbitsplitting


2p: L2,3 edge XAS

14

640 645 650 655 660

MnO

photon energy (eV)

Mn L2,3

XAS

La0.7

Sr0.3

MnO3

Spin-Orbitsplitting

Source: G. Ghiringhelli, N.B. Brookes et al unpublished Source: C. Aruta, G. Ghiringhelli et al unpublished

850 860 870 880

850 855 860

L2

Photon Energy (eV)

Ni metal

NiO

L3 L

3

Ni metal

NiO

Spin-Orbitsplitting


Atomic model

15

Total E3dTM - O

|g>

2p53dn+2L

2p53dn+1

3dn

3dn+1L

C.I. M.S.

M.S.: Multiplet

Splitting

C.I.: Configuration

Interaction

XAS probes

orbital occupation


L3 XAS and multiplets

16

Ground state

EExcitation

Resonant scattering without relaxation of intermediate state

Ground

state

Intermediate

states

Final states

Time

De- excitations

hin

h

e

out

out

2p3/2

3d

3d n 2p53d n+1

Excited states

NiO: 3d8 3d9

MnO: 3d5 3d6 Many peaks

636 638 640 642 644 646

photon energy (eV)

MnO

CuO: 3d9 3d10 One single peak

928 930 932 934

Photon Energy (eV)

CuO


L3 XAS and valence

17

Cu metal: 3d104s1

L3

L2

Cu2O: Cu1+ is 3d10

CuO: Cu2+ is 3d9

Source: M. Grioni et al PRB 45, 3309 (1992)

930 935 940

Photon Energy (eV)

CuO

Cu2O

2.1 eV

Source: M. Finazzi et al PRB 61, 4629 (2000)


X-ray absorption intensity

18

Fermi golden rule

Matrix elementJoint density of states, separatedby energy h

Electric dipole perturbation associated to a photon


Electric dipole selection rules

19

0

13

4Yruε

Radial integral

dYYdrRRr irfifif uεrε**3

Angular integral

Selection rules(via Wigner- Eckart)

Mind the nodes of R!NB what matters is Rf ,in the presence of the core hole!

mpm YYY 11

'*

2

Transitions pd

m=-1,0,+1p=-1,0,+1m’=m-1,m,m+1

l=1

l=0

l=2


Crystal field

20

Cubic

Oh

10Dq

eg

t2g

d states

xy, yz,zx

x2-y2, z2

Spherical

O3

10Dq

eg

b2yz,zx

x2-y2

z2

xy

a1

b1

Tetragonal

D4h

x

y

z Cu: x -y orbital2 2


3d split states

21

xy

z

x

y

z

xy

z

xy

z

x

y

z

x2-y2z2

xy

yz

zx

b1 a1

b2

e

eeg states

t2g states

Spherical harmonics and orbitals

22

|Y1-1|2 = |Y11|

2 |Y10|2

Y1-1=

Y11=

Y10=

2p

stat

es a

ll o

ccu

pie

d:

sph

eric

al d

istr

ibu

tio

n

3d

stat

es p

artl

y em

pty

:an

iso

tro

py

in f

inal

sta

tes

|Y2-2|2 = |Y22|

2 |Y2-1|2 = |Y22|

2 |Y20|2


2p to 3d transitions

23

• Spherical distribution

• No well defined spin state

• Spin “parallel” to orbital moment

2p3/23d

• Anisotropic occupation due to crystal field

• Possible spin polarization (FM or AF)

• Spin-orbit interaction not always negligible

photon

RCP = Y11

LCP = Y1-1

z-linear = Y10

x-linear = (Y1-1+Y11)/sqrt(2)


Transition of a hole from 3d to 2p

24

2p3/23d photon

Example: transition to a 3d(x2-y2) orbital

RCP = Y11

Final state 2p hole has main spin up character

Initial state 3d hole is100% spin down


Linear polarization of x-rays: orbital occupation

25

x

y

z

x2-y2b1

E

h in

Empty 3d state

E

High absorption

No absorption

(Y1-1+Y11)

(Y2-2+Y22)

Y10

xy

z

z2a1

E

h in

E

Weak absorption

High absorption

Empty 3d state

Y20


3d hole symmetry in cuprates

26

h E

Result: the hole in Cu2+ has 100% x2-y2 symmetry

3d9 (2p3/2)33d10


Linear polarization of x-rays: magnetization orientation

27

E

h in

Atomic spin orientation

E

Different absorption

E

h in

E

M

Atomic spin orientation

M

Same absorption

MAGNETIC LINEAR

DICHROISM:

Works for Ferro and AntiFerro


Circular polarization of x-rays and ferromagnetic materials

28

m=-1

z

RCP

m=1z

LCP

MXAS-MCD

experimental geometry

sample

E

Fermi level

3d

2pj=3/2

j=1/2

z

M

LCP

RCP

m

XAS-MCD: x-ray absorption magnetic circular dichroism

number offree states

matrixelements

transitionrates

absorption

LCP RCP

3d

2p3/2

L3

M

L3: 2p3/2 3d

L2: 2p1/2 3d


XMCD: sum rules

29

700 720 740 760 780 800 820 840 860 880 900-2

-1

0

1

2

3

4

5

6

7

8

In

tensi

ty (

arb. unit

s)

Photon energy (eV)

-10

0

10

20

30

40

L2

L3

L2

L3

Inte

gra

ted I

nte

nsi

ty (

arb. unit

s)

L2

L3

Fe

(L3+L

2)

(L3)

(L3+L

2) Co

(L3+L

2)

(L3)

(L3+L

2)

Ni

(L3) (L

3+L

2)

(L3+L

2)

For late 3dTM sum rules allow to extract spin and orbital magnetic moments

directly from spectra without the need of theoretical simulations of spectra


XAS: some examples

30

Manganite thin films

• Strain and orbital occupation

• Magnetic anisotropy (FM and AF)

STO/LAO interface

Cuprates: ferromagnetism


Films of La2/3Sr1/3MnO3: strain and phase separation

31

Manganites:

→ Mn3+/Mn4+

→ CMR

→ Phase separation

→ Orbital ordering

Mn3+: 3d4

Mn4+: 3d3

LaMnO3 Mott Hubbard Insulator:Mn – Mn fluctuations more likely than O - Mn


Manganites XAS: strain and orbital occupation

32

637 644 651 658

-0.6

-0.3

0.0

0.3

0

2

4

6

8

V-H

[a.u

.]

Photon Energy [eV]

V (E//ab)

H (E//c)

100 u.c.

XA

S (

V, H

) [a

.u.]

Linear Dichroism=IXAS//ab-IXAS//c

z-in

xzyz

eg

t2gxyxzyz

z2

x2-y2

xy

Doct

x2- y2 z2

Preferential occupation of in-plane 3dx2-y2 orbitals

637 644 651 658

-0.6

-0.3

0.0

0.3

0

2

4

6

8

V-H

[a.u

.]

Photon Energy [eV]

V (E//ab)

H (E//c)100 u.c.

XA

S (

V,

H)

[a.u

.]

xzyz

eg

t2g

x2- y2 z2

xyxzyz

x2- y2

z2

xyDoct

z-out

Preferential occupation of the out-of-plane 3dz2–r2 orbitals

LaAlO3 substrate

LAO

LSMO

c/a=1.04

SrTiO3 substrate

STO

LSMO

c/a=0.98


Manganites XAS: strain and dimensionality

33

How strain and reduced dimensionality influence magnetic and orbital anisotropies

Giacomo Ghiringhelli34

Manganites XAS: ferromagnetic behavior

XMCD: FM hysteresis loops


Manganites XAS: linear dichroism

35

LD: magnetic and orbital anisotropy


Manganites XAS: magnetic linear dichroism

36

MLD: ferromagnetic and antiferromagnetic anisotropy


Manganite superlattices

37

Koida et al, PRB 66 144418 (2002)

Bhattacharya et al, PRL 100 257003 (2008)

(SrMnO3)n/(LaMnO3)2n

LaMnO3 : Mott insulator, Mn3+, 3d4, AFM

SrMnO3 : band insulator, Mn4+, 3d3, AFM


Manganite superlattices: the effect of layer thickness

38

SrO

MnO2

MnO2

LaO

MnO2

LaO

MnO2

SrLa

OMn

n = 1, 5, 8

SMO film

LMO film

C. Adamo et al, App. Phys. Lett. 92, 112508 (2008)


LMO/SMO: linear dichroism

39

XLD at room T, no magnetic order, the dichroism isgiven only by the orbital occupation

C. Aruta, C. Adamo, A. Galdi, P. Orgiani, V. Bisogni, N. B. Brookes, J. C. Cezar, P. Thakur, C. A. Perroni, G. De Filippis, V. Cataudella, D. G. Schlom, L. Maritato, and G. Ghiringhelli, Phys. Rev. B 80, 140405(R) (2009),



40

XLD at low T,magnetic+orbital signal, we take outthe room T XLD to remain with the magnetic dichroism only




41

What do we learn about magnetic (AFM+FM) ordering?



LAO/STO XAS: measurements and and Ti4+ calc.

42

Looking for Ti3+ signal at the interface:

→ Ti4+ is 3d0

→ Ti3+ is 3d1 (like in LaTiO3)

Ti L2,3 XAS can be perfectly simulated in single ion model(just play with Slater integrals and lifetime broadening)


LAO/STO XAS: linear dichroism

43

Linear Dichroism:

LD = Iz - Ix = Ic – Iab = IH-IV

Remember : (001) surface

M. Salluzzo, J. C. Cezar, N. B. Brookes, V. Bisogni, G. M. De Luca, C. Richter, S. Thiel, J. Mannhart, M. Huijben, A. Brinkman, G. Rijnders, and G. Ghiringhelli, Phys. Rev. Lett. 102, 166804 (2009),


LAO/STO: anisotropy of empty 3d orbitals

44

→NO detectable 3d1 signal!

→In plane orbitals ar pulled down towards EF

Vacuum Interf. Bulk LAO Interf.


Interface of STO with other materials

45

458 460 462 464 466 468

-0.08

-0.04

0.00

0.04

0.08

LD

no

rm (

arb

.u.)

Photon energy (eV)

LAO

LGO

NGO

LD

The trend confirms the role of the apical oxygen at interface: LD is stronger when the overlayer has smaller lattice parameter

C. Aruta et al, unpublished

XMCD

When coupled to manganitesa 3d1 contribution appearswith ferromagnetism, revealed by XMCD

F.Y. Bruno, et al. Phys. Rev. Lett. 106 147205 (2011)


Ferromagnetic signal in cuprates

46

La2/3Ca1/3MnO3

YBa2Cu3O7

superlattice


Cuprates: weak ferromagnetism

47


Cuprates XMCD: not only a question of interface

48

Benfatto et al. PRB 74 024416 (2006)

Djaloszinsky-Moriya interaction at the origin of weak ferromagnetismin AF undoped compounds (La2CuO4). XMCD absent in Sr2CuO2Cl2.

We find XMCD in doped compounds too.


Cuprates XMCD: evaluating the canting angle

49


Second order processes

50

What about looking at the emitted x-raysafter a resonant absorption?

We can access local and collective excitations.

Electric dipole selection rules are not an obstacle.

Photon momentum can be used to probe dispersion.

h in

polarisation

x

sample y

z

h out e

spinout


RIXS: a resonant inelastic scattering

51

RIXS probes charge neutral local excitations

h in

|g>

|i>

|f>

h out

Etransferred=h in-h out

Charge Transfer

dd excitations3dn*

3dn+1L


RIXS in a metal (if it had worked...)

E

h out

EF

h in

h out -h in

J-DOS

0Eloss

The excited electron is bound:the whole process creates excitations

across the Fermi level (somehow similarly to optical

absorption).h out depends on h in.

Actually spactra a re domiated by fluorescence...


Resonant fluorescence, or XES

E

h out

EF

h in

h out

Projected DOS

The excited electron is “lost”:its final energy is not importantand the emission spectrum is

independent of h in.


RIXS works well if there is a gap

E

EF

h out -h in

Charge excit.:continuum

0Eloss

Charge neutral excit.:sharp peaks in the gap

EExcitation

Resonant scattering without relaxation of intermediate state

Ground

state

Intermediate

states

Final states

Time

De- excitations

hin

h

e

out

out

Strongly correlatedsystems usually

give nice RIXS spectra

Gapped systems:

Excitations insidethe gap


Low energy excitations in L2,3 edge RIXS

-7 -5 0-6 -4 -3 -2 -1 1

(C)

Relative emitted energy (eV)

Inte

nsity (

arb

. units)

excited states

Energy loss

elas

tic


Electronic, magnetic and vibrational excitations in RIXS

1meV 10meV 100meV 1eV 10eV

Electronic

Magnetic

Phonons

ddCT

Optical gap

What excitations can we observe by RIXS?


L edge RIXS : energy and momentum transfer

Resonant Inelastic X-ray Scattering:

• an energy loss experiment

• made with photons of high energy

• at a core absorption resonance

k’

k

q = k-k’

h = E - E’

Energy

Momentum

E’, ’, ’k

E, , k

Scattering plane

S amp le

Conservation laws:

• Energy

• Momentum

• “Angular momentum”


Photon momentum and kinematics

1m 10m 100m 1 10 100 1k 10k 100k

1E-3

0.01

0.1

1

10

k (

Ang

-1)

energy (eV)

Wavevector of particles used in inelastic scattering

Thermal

neutrons

M e

dg

es

L e

dg

es K

ed

ge

s

Neutrons

Pho

tons

1st Brillouin zone boundary

Photons vs Neutrons: energy and momentum


Cuprates: the “easy” case

59

In cuprates Cu is divalent: Cu2+ 3d9

This makes XAS almost trivial: 1 peak only

3d9 (2p3/2)33d10

928 930 932 934

Photon Energy (eV)

CuO

RIXS can be calculated even by hand:

3d9 (2p3/2)33d10 (3d9)*

Even for magnetic excitations (spin waves), because fast collision approximation is a very good approximation


CubicOh

10Dq

eg

t2gxy, yz,zx

x2-y2, z2

SphericalO3

10Dq

eg

b2yz,zx

x2-y2

z2

xy

a1

b1

TetragonalD4h

d states

Interatomic exchange

10Dq

eg

b2yz,zx

z2

xy

a1

b1

x2-y2

dd excitations in Cu2+ systems

3d9 2p53d10 3d9


Cu L3 edge RIXS: CuO, La2CuO4, Malachite

61

-3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0

0

7

14

21

Inte

nsi

ty(p

h.s-1

eV

-1)

Energy loss (eV)

CuO

La2CuO

4

Cu2(OH)

2CO

3

x2Different Cu2+

coordination, symmetry,

hybridization

Different dd excitations

Cu2+ in squareapproximately

planar coordination

Cu-O distances:

CuO 1.7 – 2-2 Ang

LCO 1.9 – 2.4 Ang

Malachite 1.9 – 2.6 Ang


Layered cuprates

M. Moretti Sala, V. Bisogni, L. Braicovich, C. Aruta, G. Balestrino, H. Berger, N. B. Brookes, G.M. De Luca, D. Di Castro, M. Grioni, M. Guarise, P. G. Medaglia, F. Miletto Granozio, M. Minola, M. Radovic, M. Salluzzo, T. Schmitt, K.-J. Zhou, G. Ghiringhelli, New J. Phys. 13, 043026 (2011)

By using the calculated RIXS cross sections to fit the data the energy of all the 3d orbitals can be obtained from teh RIXS spectra for any compound.


Ni L3 edge: NiO, NiCl2

63

Ni2+ (3d8) in octahedral

coordination

-4 -3 -2 -1 00

20

40

Inte

nsi

ty(p

h.s-1

eV

-1)

Energy loss (eV)

NiO

NiCl2

a

b

c

xy

z

a b

c

x y

z


Ni2+ in NiO: dependence on incident photon energy

64

G. Ghiringhelli et al , Phys Rev Lett 102, 027401 (2009)

852 853 854 855 856 857 858

852 853 854 855 856 857 858

-5

-4

-3

-2

-1

0

5

4

3

2

1

0

0 25 50 75 100852 853 854 855 856 857 858

0

1

2

3

4

5 NiORIXS

Energ

ylo

ss(e

V)

Incident photon energy (eV)

S

Inte

nsi

ty(a

rb.u

.)

NiONi L

3 XAS

P

NiO

PS P

RIXS Intensity (ph. s-1

eV-1

)

Energ

ylo

ss(e

V)

NiCl2

x5


Many excited states

65

Crystal field model: Sugano-Tanabe diagrams

0.0

0.5

1.0

1.5

0.0

0.5

1.0

1.5

0.00.51.01.52.02.53.03.54.0

1E

g1T

2g

3T

1g

1T

1g

1T

2g

3T

1g

1A

1g

3T

2g

1E

1g

3A

2g

1G

3P

1D

relative state energy (eV)

10D

q(e

V)

3F

10D

q(e

V)

3F

1D

3P

1G

-4.0 -3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0

H

relative scattered photon energy (eV)

inte

nsit

y(a

rb.u

.)

F

Ni L3 RIXS

(x2-y2), (z2)

(xy), (yz), (zx)

eg

t2g

10Dq

Single ion

Octahedral C.F.

3d spin-orbit

Exchange

Single ion

Octahedral C.F.

G. Ghiringhelli et al, J. Phys. Cond. Mat. 17, 5397 (2005) S.G.Chiuzbaian, G. Ghiringhelli et al, Phys. Rev. Lett. 95, 197402 (2005)


Mn L3 edge: MnO, LaMnO3

66

Mn2+ and Mn3+

in octahedral

coordination

-10 -5 0

0

5

10

15

LaMnO3

Inte

nsi

ty(p

h.s-1

eV

-1)

Energy loss (eV)

MnO

x10

Mn2+: 3d5

Mn3+: 3d4


An application to thin film: Mn2+ in LaxMnO3

LaxMnO3-d/STO filmsx=La/Mn ratiofor x<1 becomes FM (self doping)

MnOx=0.66x=0.88x=0.98x=1.07

XAS reveals the presence of Mn2+ for x<1

RIXS shows that Mn2+ is at site A, ie, it replaces La3+

P. Orgiani, A. Galdi, C. Aruta, V. Cataudella, G. De Filippis, C.A. Perroni, V. Marigliano Ramaglia, R. Ciancio, N.B. Brookes, M. Moretti Sala, G. Ghiringhelli, and L. Maritato, Phys. Rev. B 82, 205122 (2010)


STO/LAO superlattice: RIXS at Ti L3

68


600

500

400

300

200

100

0

-8 -6 -4 -2 0

Energy loss (eV)

Sr2CuO2Cl2

Cuprates: not only dd excitations


(0,0) ( ,0)

( , )

RECIPROCAL SPACE

nuclear BZ

magnetic BZ

La2CuO4: 2D spin ½ Heisenberg AF insulator

CopperOxygen

DIRECT SPACE

Elementary magnetic excitations are spin waves


-3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5

Energy loss (eV)

La2CuO4

SAXES

Swiss Light Source


&

Dispersing peaks: magnetic excitations


R. Coldea et al, Phys. Rev. Lett. 86, 5377 (2001).

La2CuO4

L. Braicovich, J. van den Brink, V. Bisogni, M. Moretti Sala, L. Ament, N.B. Brookes, G.M. de Luca, M. Salluzzo, T. Schmitt, and G. Ghiringhelli PRL 104 077002 (2010)

LCO, comparing with INS: these are magnons!


Sr2CuO2Cl2

M. Guarise, B. Dalla Piazza, M. Moretti Sala, G. Ghiringhelli, L. Braicovich, H. Berger, J.N. Hancock, D. van der Marel, T. Schmitt, V.N. Strocov, L.J.P. Ament, J. van den Brink, P.-H. Lin, P. Xu, H. M. Rønnow, and M. Grioni. Phys. Rev. Lett. 105, 157006 (2010)

Another example: magnons in SCOC


What happens in doped, SC cuprates? NdBCO

300

200

100

0

-100

-200

Inte

nsity (

a.u

.)

-0.6 -0.4 -0.2 0.0 0.2

Energy (eV)

Insulating (annealed)Superconducting: Tc= 65K

300

200

100

0

-100

-200

Inte

nsity (

a.u

.)

-0.6 -0.4 -0.2 0.0 0.2

Energy (eV)


YBCO and NdBCO family (Keimer, Le Tacon)


Theory of magnetic RIXS (1)

76

Single ion cross section Linear spin wave theory


Theory of magnetic RIXS (2)

77


CaCuO2/SrTiO3 superlattice: superconductor

78

D. Di Castro, M. Salvato, A. Tebano, D. Innocenti, P. G. Medaglia, M. Cirillo, and G. Balestrino, arXiv1107.2239v1 (2011)


CaCuO2/SrTiO3 superlattice: RIXS

79

M. Minola, D. Di Castro, G. Ghiringhelli, M. Moretti Sala, N. B. Brookes, P.G. Medaglia, A. Tebano, G. Balestrino and L. Braicovich, unpublished

0

20

40

60

80

100

CCO bulk

SL n=2

SL n=3

N

orm

. In

ten

sity (

arb

. u

.)

Energy Loss (eV)

3.0 2.5 2.0 1.5 1.0

0

100

200

300

400 SL n = 2

SL n = 3

bulk CCO

0 3.01.0 2.52.01.5

Energ

y (

meV

)q//

0.5


With high resolution L edge RIXS

We can probe orbital and magnetic excitations

In layered cuprates we can map E(q) of magnons and

we can thus complement optical spectroscopy, EELS and INS

EXPERIMENTSthe limitations are still E resolution and intensity.

Instrumentation and perspectives

AXES at the ESRF SAXES at the SLS


L

Same optical scheme:

• VLS spherical grating

• CCD detector

Different length

Since 1994: AXES at beam line

ID08 of the ESRF

L = 2.2 m

Design: E/ E = 2,000 at Cu L3 (930 eV)

2010: E/ E = 5,000 at Cu L3

dvanced -Ray miss ion pectroscopyE SA X

INFM

C. Dallera et al. J. Synchrotron Radiat. 3, 231 (1996)G. Ghiringhelli et al., Rev. Sci. Instrum. 69, 1610 (1998)M. Dinardo et al., Nucl, Instrum. Meth A 570, 176 (2007)

SAXES

Swiss Light Source


&

Since 2007: SAXES at beam line

ADRESS of the SLS

L = 5.0 m

Design: E/ E = 12,000 at Cu L3

2008: E/ E = 10,000 at Cu L3

G. Ghiringhelli, et al Rev. Sci. Instrum. 77, 113108 (2006)V. Strocov, T. Schmitt, L. Patthey et al, J. Synch. Rad., 17, 631 (2010).

From AXES (ESRF, ID08) to SAXES (SLS, ADRESS)


The future of RIXS instrumentation

82

E down to 30 meV at Cu L3

and 10 meV at Ti L3

10 m

ЄRIXS:The Єuropean RIXS facility (N.B Brookes)

Other high resolution RIXS projects:

• Centurion, at NSLS II (Brookhaven Nat Lab)

• Diamond (UK)

• MAX IV (Sweden)

• NSRRC (Taiwan)

• ...


Bibliography

83

x-ray absorption spectroscopy

Education

ghiringhelli et

mev7 giacomo ghiringhelli

photons5 giacomo ghiringhelli

d4h20giacomo ghiringhelli

photon18giacomo ghiringhelli

summary4giacomo ghiringhelli

p states

resonant inelastic xray