Transcript Slide 1

Tackling multiferroic YMnO3 and BiFeO3 in BM25
17-APR-2012, http://usuaris.tinet.cat/~xmarti/talks
X. Marti, V. Holy
Charles University, Prague
P. Ferrer, T. Schulli
ESRF, Grenoble
J. Herrero-Albillos
BESSY, Berlin
J. Narvaez, G. Catalan
CIN2, Barcelona
N. Barrett,
CEA, Gif-sur-Yvette
M. Alexe
MPI, Halle
[email protected]
SKIN
BiFeO3
(AF, FE)
=
BULK
http://usuaris.tinet.cat/~xmarti/talks
Tackling multiferroic YMnO3 and BiFeO3 in BM25
17-APR-2012, http://usuaris.tinet.cat/~xmarti/talks
X. Marti, V. Holy
Charles University, Prague
P. Ferrer, T. Schulli
ESRF, Grenoble
J. Herrero-Albillos
BESSY, Berlin
J. Narvaez, G. Catalan
CIN2, Barcelona
N. Barrett,
CEA, Gif-sur-Yvette
M. Alexe
MPI, Halle
[email protected]
Something
SKIN
BiFeO3
(AF, FE)
=
BULK
http://usuaris.tinet.cat/~xmarti/talks
Courtesy of G. Catalan
1. Small changes of the out-of-plane parameter
2. …and confined in a few (?) nm thick topmost surface
Ei
αi
BiFeO3
http://henke.lbl.gov/optical_constants/
[email protected]
Correction for refraction
Z: perpendicular to surface
Two exit angles: αf , Ψ
(i.e. latitude, longitude)
Ei
αi
Primary beam
X
Y
Pseudocubic reciprocal space coordinates :
qx = K * [ cos(αf) * cos(Ψ) - cos(αI) ] ~ H
qy = K * [ cos(αf) * sin(Ψ) ] ~ K
qz = K * [ sin(αf) + sin(αI) ] ~ L
K = 2*π/λ


Qz  K (sin(i )  sin( f )), qz  K sin 2 (i )  2(1  n)  sin 2 ( f )  2(1  n) .
  1 / Im(qz ), L  az Re(qz  Qz ) /(2 ),
[email protected]
http://usuaris.tinet.cat/~xmarti/talks
1. Small changes of the out-of-plane parameter
2. …and confined in a few (?) nm thick topmost surface
http://henke.lbl.gov/optical_constants/
1. Small changes of the out-of-plane parameter
2. …and confined in a few (?) nm thick topmost surface
To circumvent
refraction we
scanned both
energy and
incidence angle
The inter-planar distances are a fingerprint of each material/phase/skin
10
log(Intensity)
-1
Qz (Å )
0.5
0.45
5
0.4
-0.1
0
0
0.1
Q (Å-1)
x
Periodicites and directions
0.4
0.45
Q (Å-1)
0.5
Only periodicities
Pseudocubic reciprocal space coordinates :
qx = K * [ cos(αf) * cos(Ψ) - cos(αI) ] ~ H
qy = K * [ cos(αf) * sin(Ψ) ] ~ K
qz = K * [ sin(αf) + sin(αI) ] ~ L
K = 2*π/λ
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Q  qx  q y  qz  d hkl
2
2
2
http://usuaris.tinet.cat/~xmarti/talks
[email protected]
BULK
SKIN
Changing the energy
(no refraction correction required)
Q
(no alignment required)
There is a skin layer
THICKNESS < 40 nm
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BULK
SKIN
Changing the energy
(no refraction correction required)
shift
splitting
Q
(no alignment required)
There is a skin layer
THICKNESS < 40 nm
Measured
BULK
Corrected
SKIN
Changing the energy
(no refraction correction required)
Q
Q
There is a skin layer.
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THICKNESS < 40 nm
Measured
BULK
Corrected
SKIN
Changing the energy
(no refraction correction required)
Changing the angles
There is a skin layer.
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THICKNESS < 40 nm
X-ray diffraction
Impedance
(Å)
1.015
1.01
300 K
Q/Q
Bulk sensitive
Surface sensitive
1.005
1
50
100
150
200
250
Temperature (K)
300
Heat capacity and magnetic susceptibility
100
Temperature dependence (low temperature)
Independent of polishing process
-1
0.04
-1
40
0.03
-1
-1
60
'(emuOe mol )
Ac anomalies seen in 3 samples by 3 different
growers !!!
80
Cp (J mol K )
The skin has its own phase transitions
0T
1T
20
0.02
0.01
0.00
0
100
150
200
250
300
T (K)
0
0
50
100
150
T (K)
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50
200
250
300
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r
YMnO3
I. Fina, F. Sanchez, J. Fontcuberta, ICMAB
J. Ander Gallastegui, F. Jimenez Villacorta
13.3 140 nm
9.6 70 nm
8.1 28 nm
13.1
9.4
7.9
12.9
9.2
7.7
-200
-100
0
100
200 -200
-100
200 -200
-100
8.0
7.9
8.0
7.9
More FE
2.0
2.1
H (r.l.u.)
Less FE
O
Mn
200
7.9
O
Mn
100
8.0
2.1
2.0
2.1 2.0
K (r.l.u.)
H (r.l.u.)
2.0
2.1
K (r.l.u.)
0
E (kV/cm)
L (r.l.u.)
L (r.l.u.)
L (r.l.u.)
100
E (kV/cm)
E (kV/cm)
2.0
2.1
H (r.l.u.)
0
Mn
Mn
2.0
2.1
K (r.l.u.)
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YMnO3
I. Fina, F. Sanchez, J. Fontcuberta, ICMAB
J. Ander Gallastegui, F. Jimenez Villacorta
More FE
Less FE
O
O
Mn
Mn
Mn
Mn
YMnO3
I. Fina, F. Sanchez, J. Fontcuberta, ICMAB
J. Ander Gallastegui, F. Jimenez Villacorta
Strained YMnO3 thin films
EXAFS
L
XRD
S
d
Bonding angle
Magnetic properties
Ferroelectric properties
O
O
Mn
Mn
Mn
Mn
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(a)
(b)
FT Module
Fitting
106 nm
FT Magnitude
3
-2
k ·(k) (Å )
106 nm
49 nm
49 nm
EXAFS
Mn-O d=1.90 Å
Mn-O d=2.14 Å
3
EXAFS k (k)
3
Filtered k (k)
Fitting
Mn-O d=1.90 Å
Mn-O d=2.14 Å
4
6
8
10
12
-1
Wavenumber (Å )
1
2
Distance (Å)
3
L
(c)
35.00
2.16
(d)
35.00
2.14
30.00
30.00
25.00
20.00
2.15
Long bond (Å)
Long bond (Å)
25.00
15.00
9.000
x
2.14
2.13
20.00
2.13
15.00
9.000
x
2.12
2.11
106 nm
1.89
1.90
1.91
Short bond (Å)
1.92
49 nm
1.89
1.90
1.91
Short bond (Å)
1.92
S
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2.22
2.2
sp
ir
al
,P
Bulk YMnO3
2.14
2.12
L (Å)
EXAFS
XRD
|| c
2.18
2.16
155
E-type, P || a
150
More FE
145
L
140
Bonding angle
Magnetic properties
Ferroelectric properties
A-type, no P
S
d
106 nm
Epilayers
YMnO3
49 nm
Less FE
135
2.1
1.85
1.9
S (Å)
1.95
More FE
Less FE
O
O
Mn
Mn
Mn
Mn
SKIN
Strained YMnO3 thin films
(a)
(b)
BiFeO3
(AF, FE)
FT Module
Fitting
=
106 nm
XRD
FT Magnitude
EXAFS
3
-2
k ·(k) (Å )
106 nm
49 nm
L
49 nm
(a)
S
[100]
d
(c)
L
S
L
Mn-O d=1.90 Å
Mn-O d=2.14 Å
S
Bonding angle
Mn-O d=1.90 Å
EXAFS k (k)
S
Magnetic
Mn-O d=2.14 Å
(k)
Filtered k properties
Fitting
Ferroelectric properties L
3
L
3
1
12
10
8
6
-1
Wavenumber (Å )
4
S
3
2
Distance (Å)
E
S
L
[010]
(c)
(b)
35.00
2.16
30.00
2.15
35.00
30.00
25.00
20.00
Long bond (Å)
Long bond (Å)
25.00
(d)
2.14
15.00
[001]
9.000
x
2.14
2.13
2.13
O
L
1.91
Short bond (Å)
1.92
[001]
15.00
9.000
2.12
Mn
D
106 nm
1.90
20.00
θ
x
2.11
1.89
S
1.89
1.90
Mn
[110]
1.91
Short bond (Å)
49 nm
1.92
[110]
BULK
Tackling multiferroic YMnO3 and BiFeO3 in BM25
17-APR-2012, http://usuaris.tinet.cat/xmarti/talks
[email protected]
THANKS FOR YOUR ATTENTION !!
-EXAFS:
-bonding angle in YMnO3 films increases with decreasing strain
- Grazing incidence:
evidences a BiFeO3 skin layer.
SKIN
Strained YMnO3 thin films
(a)
(b)
BiFeO3
(AF, FE)
FT Module
Fitting
=
106 nm
XRD
FT Magnitude
EXAFS
3
-2
k ·(k) (Å )
106 nm
49 nm
L
(a)
S
[100]
Mn-O d=1.90 Å
Mn-O d=2.14 Å
49 nm
d
Mn-O d=1.90 Å
Mn-O d=2.14 Å
S
Bonding angle
EXAFS k (k)
S
Magnetic
(k)
Filtered k properties
Fitting
Ferroelectric
properties L
3
L
3
1
12
10
8
6
-1
Wavenumber (Å )
4
(c)
L
S
L
S
3
2
Distance (Å)
E
S
L
[010]
(c)
(b)
35.00
2.16
30.00
(d)
2.14
30.00
25.00
20.00
Long bond (Å)
Long bond (Å)
25.00
2.15
35.00
15.00
[001]
9.000
x
2.14
2.13
2.13
O
L
1.91
1.92
15.00
9.000
Mn
D
2.11
1.90
Short bond (Å)
20.00
[001]
θ
x
2.12
106 nm
1.89
S
1.89
1.90
Mn
[110]
1.91
Short bond (Å)
49 nm
1.92
[110]
BULK