Page 1
Oxydes de métaux de transition: réseaux carrés et triangulaires
pour générer de nouvelles fonctionnalités
Laboratoire CRISMATCRIstallographie
et Sciences des MATériaux
Unité
Mixte de Recherche n°6508 CNRS/ENSICAEN
Antoine Maignan
Collége
de France, Chaire de Physique de la Matière CondenséeAntoine Georges, Cours 6: transition métal-isolant de Mott
dans
les oxydes de métaux de transition
Page 2
Why
are we
interested
in oxides
?plenty
of cation combinations
(playground
for Chemists)
natural
abundancegreen materials
«
air prepared
»
(Pb free etc…)
applications: microelectronics: dielectrics
(HfSiO2
) , ferroelectrics(SrBi2
Ta2
O9
),
QTM quantum computing
(Ca3
Co2
O6
) ?
energy: (TCOs
for PV ITO, Li-batteries Lix
CoO2
, SOFC H2(La,Sr)(Co,Fe)O3-d
, catalysis
nanomaterials
to replace PtRh, superconductivity
YBa2
Cu3
O7
, thermoelectricity
?)
FeRam TEG
Page 3
Plan:
3D magnetic
networks:CMR in perovskite
manganites
MIT in cobaltitesFrustrated
lattices
of the «
114
»
type
1D and 2D TM-O-TM
networks: hexagonal perovskitesand CdI2
type structures
n-type vs p-type
conductivity
in oxides
Page 4
Introduction
Perovskite: very
rich
system!Structures and properties!!
T (K)0 50 100 150 200 250
ρ (Ω
.cm
)
10-2
10-1
100
101
M (µ
B)
0
1
2
3
4
RB
=0/R
B=5
T
ρ (Ω
. cm
)
T (K)
0
5T
0 50 100 150 200 25010-2
10-1
100
101
102
50
100
150
200
CMRStrong
coupling
between
structures,transport
and magnetism.
ABO3
Page 5
A-site (Ln, A)
O
B-site (Mn)
Perovskite
structure
Flexibility
of the structure with
regard to cationic
and
anionic
replacements and tolerance
to ion defects.
aP
ABO3
AO and BO frameworks
Page 6
Spin-Charge-Orbital coupling
Ln
3+x Ca 2+
1-x Mn
3+1-x Mn
4+
x O3Ln
3+x Ca 2+
1-x Mn
3+1-x Mn
4+
x O3
Page 7
Square-shaped window
Tilting
Diamond-shaped window
No tiltingNo tilting
Page 8
Distortiont > 1 → hexat = 1 → cubict < 0.96
→ orthorhombic
…)(2),(
OMn
OALn
rrrr
t+
+=
Tolerance factorGoldschmidt
factor
-
manganese valency
(Mn3+/Mn4+)-
average A-site cationic radius (<rA
>)
Ln
3+x Ca 2+
1-x Mn
3+1-x Mn
4+
x O3
(Ln,A)-O and Mn-O interatomic
distances
AO / BO frameworks
if O3 !!
Page 9
Fixed
Mn valence
Ln0.7
A0.3
MnO3
Fixed
<rA
> = 1.255 Å
#Nd0.7
Ba0.3
MnO3
propertiesTh0.35
(Bax
Sry
Caz
)MnO3
A-site disorderσ2
= Σyi
ri2-<rA
>2
Page 10
x ( P r1 - x
C ax
M n O3
)
0 . 0 0 . 1 0 . 2 0 . 3 0 . 4 0 . 5 0 . 6 0 . 7 0 . 8 0 . 9 1 . 00 .
0 . 5
PrMnO3
. 0
1 . 5
2 . 0
2 . 5
3 . 0
3 . 5
1 5 0
2 0 0
2 5 0
3 0 0
TC
M4K
(μB
/ mol
. Mn)
T(K
)
TN
CMR CMR
FMI
CO
AFM
I
CG
TN
TCO
CaMnO3
100
50
0
Manganites : Complex
magnetic
and electronic
phase diagram
Page 11
Magnetic
properties
: magnetization, susceptibility….
… Correlated
withtransport properties 0.95
0.85
0.925
0.975
Sm1-xCaxMnO3
0 50 100 150 200 250 3000.0
0.2
0.4
0.6
0.8
1.0
1.2
0.87
0.80M (µ
B/f.u.
)
0.83
0.75
T (K)
J. Solid State Chem. 134, 1, 198 (1997)
Phys. Rev. B 60, 14057 (1999)
0 50 100 150 200 250 3000.005
0.010
0.015
0.020
0.8
1.0
1.2
1.4
1.6
1.8
0
7T
0 50 100 150 200 250 30010-4
10-3
10-2
10-1
100
101
102
103
100
101
102
103
104
105
0
7T
0 50 100 150 200 250 30010-4
10-3
10-2
10-1
100
101
102
103
104
105
0
2
4
6
0
ρ 0/ρ
7T
7T
x = 0.90
x = 0.85x = 0.80
Page 12
x=0.07
x=0.10
x=0.12
0 50 100 150 200 250 300 350 400
0.005
0.010
0.015
0.020
χ' (e
mu.
fu-1
)
f=100Hzhac=3 Oe
T(K)
0 50 100 150 200 250 300 350 4010-1
101
103
105
107
109
Elec
tric
al r
esis
tivity
(m
Ωcm
)
T (K)
0.10
0.08
0.07
0.12 0.15
CaMn1-x
Mox
O3
Ex1Impurity
induced
CO
Page 13
20 29 38 47 56 65 74 83 92 101
-1000
6000
13000
20000
27000
34000
41000
48000
55000
62000
2 Theta (deg.)
Inten
sity (
a.u.)
101
020
200
121
002
201
102
211
112
031Pnma
P21/m
1.5K
305K
201,
102
101
020
101,
020
200,
-121
,002
-201
,-102
-211
,-112
-101 12
1
211 ,
130,
031,
112
220,
022
TN
TOO
CaMn0.9
Mo0.1
O3magnetism
[TN
]and
structure [TOO
] vs.
T
ND-LLB-G4 1 f (T)
Ex1
Page 14
a b002
002
200
CaMn0.9
Mo0.1
O3ME f(T)
DE 300K 90K image
0 50 100 150 200 250 300 350 40010-1
101
103
105
107
109
Elec
tric
al r
esis
tivity
(m
Ωcm
)
T (K)0 50 100 150 200 250 300 350
-350
-300
-250
-200
-150
-100
-50
0
50
100
Ther
moe
lect
ric p
ower
(μV
K-1)
T (K)
Propriétés
physiques f(T)
T (K)0 50 100 150 200 250 300
M ( μ
B/f.
u.)
0.010
0.012
0.014
0.016
0.018
0.020
0.022
0.024
0.026
Pnma P21
/m
Ex1
Page 15
CaMn1-x
Mox
O3
Ex1
Page 16
Charge and orbital Ordering
e.g. Pr0.5
Ca0.5
MnO3
Mn3+ Mn4+Insulating
Antiferromagnet
Metallic
Ferromagnet
H > 25 T
Page 17
M (μ
B/f.
u)
0 20000 40000 60000 800000,0
0,2
0,4
0,6
0,8
1,0
1,2
1,4
1,6
T=2.5K
3
2
1
H (Oe)
Pr0.5
Ca0.47
Ba0.03
MnO3
Manganites : successive M(H) at
2.5 K, T= 300K
The ferromagnetic
fractiondecreases
with
the number
of
thermal cycling
: history
effect
Page 18
μ0H(T)
3
2
1
T=2.5K
0 1 2 3 4 50
1
2
3
4M
(μB/f.
u) Pr0.6
Ca0.4
Mn0.99
Cr0.01
O3
μ0H(T)0 1 2 3 4 5
0
1
2
3
4
32
1
T=2.5 K
M (μ
B/f.
u)Pr0.6
Ca0.4
Mn0.98
Ga0.02
O3
μ0 H(T)0 1 2 3 4 5
0
1
2
3
4
31
T=2.5 K
M (μ
B/f.
u)
Pr0.6
Ca0.4
Mn0.96
Ga0.04
O3
Characteristic
H of the steps
:irreproducibility
Page 19
3.2 3.4 3.6 3.8 4.0 4.2 4.4
2.4
2.6
2.8
3.0
3.2
T = 1.5 K
M (μ
Β / f.u
.)
μ0Η(Τ)
At even lower T, additional steps : no characteristic scalesas expected in MT like transition
Influence of the temperature
Avalanches
Page 20
Magnetization Steps
No “critical fields”
strictly speakingNo specific magnetization values associated with the plateaus
Stepwise growth of the FM phase at the expense of the AFCOO phase ?
AFC00
FM Hintermediate
states
Page 21
Ex4’Phase separation
Page 22
Plan:
3D magnetic
networks:CMR in perovskite
manganites
MIT in cobaltitesFrustrated
lattices
of the «
114
»
type
1D and 2D TM-O-TM
networks: hexagonal perovskitesand CdI2
type structures
n-type vs p-type
conductivity
in oxides
Page 23
LBaCo2
O5.5
123
112
Oxygen
and cation ordering: ordered
perovskite
Page 24
TMI
=300K
210 50 100 150 200 250 300 350 400
10-3
10-2
10-1
100
101
102
103
104
105
T(K)
ρ(Ω
.cm
)
HoBaCo2
O5.5
LnBaCo2
O5+x
: x=0.5, pure trivalent cobalt, TMI
=f(rA
)trivalent Ho and Y same ionic radius (0.1072 and 0.1075nm)
Hole
vs Electron asymmetry
0T
0 50 100 150 200 250 300
0
50
100
150
7T
0T
S( μ
V.K
-1)
T(K)
0 50 100 150 200 250 300
0
50
100
150
200
TEP sign change at TMI
from metal S = -2 μV.K-1
(e-) to insulator S>>0 (h+)
Page 25
Possible spin blockade in 112High T : an eg
electron Co2+
can movein a background of IS/HS Co3+
Broad eg
band , S<0 and small abs. value
Low T : an eg
electron Co2+
cannot move in a background of LS Co3+
, requires to flip other spins, wrong spin-states LS Co2+ and IS Co3+
instead of LS
Low T : a tg
hole Co4+
can hopin a background of LS Co3+
, Localization of heavy holes as T decreases, S>>0
A. Maignan et al, Phys. Rev. Lett. 93, 026401 (2004)
« Co3+
»
-
112 cobaltites
Page 26
CuO
tenorite
oxidespiral induced electric polarization in the 213K-230K range
where an incommensurate antiferromagnetic
structure is observedC2/c monoclinic
structure (distorted
NaCl
struct.)
Page 27
c c
Y
BaO (Fe,Cu)O2
a b FeO2
CuO2
112-
YBaCuFeO5
ordered
perovskite
(Y/BaO), isostructural
to YBaCo2
O5
Do Fe and Cu order
?
P4/mmm P4mm
Kundys B et al., APPLIED PHYSICS LETTERS 94 , 072506 2009
Page 28
0 50 100 150 200 250 300
0.0
0.1
0.2
0.3
0.4
0
20
40
60
80
100
120
1407.6
7.8
8.0
8.2
8.4
8.6
0
200
400
600
(c)
Cur
rent
(pA/
cm2 )
Pola
rizat
ion(
ΔP(µ
C/c
m2 ))
T(K)
(b)100kHz
10kHz
5kHz
ε'
(a)
H = 0.3 Tχ
(em
u.g-1
)*10
6
YBaCuFeO5
TN2
Magnetoelectric
coupling
Incommen.Antiferro.
CommensurateAntiferromagnet
Paramagnetic
Complex
IncommensurateAF structure
Page 29
Plan:
3D magnetic
networks:CMR in perovskite
manganites
MIT in cobaltitesFrustrated
lattices
of the «
114
»
type
1D and 2D TM-O-TM
networks: hexagonal perovskitesand CdI2
type structures
n-type vs p-type
conductivity
in oxides
Page 30
3 Co(2) : kagomé
1 Co(1) : triangular
LnBaCo4
O7
vCo
= 2.25 3Co2+
: 1Co3+
Charge ordering ?
Network ofCoO4
tetrahedra
kagome
Page 31
Co cations: 2 frustrated
magnetic
networks
kagome pyrochlore
Page 32
YbBaCo4
O7
and YbBaCo4
O8
100 150 200 250 3006.255
6.260
6.265
6.270
6.275
a (Å
)
T (K)
Space
group P63
mc , a ≈
0.63 nm, c ≈
1.03 nm
TS
100 150 200 250 300 350120
140
160
180
200
220
240
260
Y3+Yb3+
0.5Y3+
0.5Yb3+
Y3+
Yb3+0.5Y
3+0.5
Yb3+
rL3+(nm)
T S(K
)
S(μV
/K)
T(K)
0.0860.0870.0880.0890.090160180200220240260280300320
LBaCo4
O7
: ionic
radius of L3+
controls
TS
Page 33
0 50 100 150 200 250 300 350
1x104
2x104
3x104
4x104
ParamagnetismAF fluctuations
shortrangeAF
AF
TN
TSP31cPbn21
χ-1 (g
.em
u-1)
T (K)
YbBaCo4
O7
: from
geometric
frustation
to long–range
AF
Geometric
frustration lift by a first-order
structural transition
Page 34
Formula sum CaBaCo4 O7
Formula weight 525.134
g/mol
Crystal system orthorhombic
Space group P b n 21 (33)
Cell parameters a=6.2872(2)
Å
b=11.0043(3)
Å
c=10.1913(2)
Å
Cell volume 705.10(3)
Å3
Calc. density 1.23664
g/cm3
Atom x y z
Ca 1/2 1/2 1/2 4b
Ba 1/4 3/4 3/4 4c
Co1 0 0.1209 0.1209 16e
O1 0 0 3/4 24f
O2 1/4 1/4 3/4 4d
CaBaCo4
O7
Distortion
Page 35
CaBaCo4
O7 Ferrimagnetic
Page 36
0 50 1000,0
5,0x10-31,0x10-21,5x10-22,0x10-22,5x10-23,0x10-23,5x10-24,0x10-24,5x10-25,0x10-25,5x10-26,0x10-2
40 50 60 70 80
0,05,0x10-3
1,0x10-2
1,5x10-2
2,0x10-2
2,5x10-2
3,0x10-2
3,5x10-2
4,0x10-2
4,5x10-2
5,0x10-2
χ (e
mu.
g-1)
T (K)
0,003 0,004 0,005 0,006 0,007101
102
103
104
105
106
ρ (Ω
.cm
)
T-1 (K)
zfc fcc fcw
χ (e
mu.
g-1)
T (K)
0 10 20 30 40 50 60 70 80 90 100
10
12
14
16
18
20
22
24
26V517, Bias Field 1V, 1K/min
ε'
T(K)
5kHz (1K/min) 10kHz (1K/min) 50kHz (1K/min) 100kHz (1K/min)
0 10 20 30 40 50 60 70 80 90
10
12
14
Ferrimagnetic
114
0 10 20 30 40 50 60 70 80 90
-80
-60
-40
-20
0
20
40
60
80
P(μ
C/m
2 )
T(K)
+111kV/m -111kV/m
TC
TC
Spin induced
ferroelectric
Page 37
Plan:
3D magnetic
networks:CMR in perovskite
manganites
MIT in cobaltitesFrustrated
lattices
of the «
114
»
type
1D and 2D TM-O-TM
networks: hexagonal perovskitesand CdI2
type structures
n-type vs p-type
conductivity
in oxides
Page 38
hexagonal perovskiteABO3
Page 39
A=Ba
Ba
Hexagonal close packed
stacking
of the AO3
layersEvery
AO3
unit, one octahedron
is
created, occupiedby Co4+
Hexagonal Perovskites2H-BaCo4+O3 : a 1D compound with
edge-shared
CoO6
octahedra
The chains
of CoO6
octahedra
forma triangular
array
M. Parraset al, J. Solid State Chem. 120 , 327 (1995)
Page 40
Alternating
hexagonal (h) and cubic
(c) stackingof the AO3-δ
layers
(hhhccc) yields
the 12-HCreation
of CoO4
tetrahedra
3D array
of CoOn
polyhedra
12H-Ba0.9
Co+3.2O2.6 : units
of edge-shared
CoO6
octahedra
bridgedby CoO4
tetrahedra
A.J. Jacobson et J.L. Hutchison, J. Solid State Chem. 35, 334 (1980)K. Boulahya et al , Phys. Rev. B 71, 144402 (1999)
Page 41
12H-Ba0.9
Co+3.2O2.6 : structure
Transmission electronmicroscopy
: hhhccc
EDS coupled
to ED :Ba/Co = 0.9 ratio
X-ray diffraction :12H, P63/mmca=0.56612 (1) nmc=2.84627 (8) nm
A. Maignan et al , J. of Solid State Chem. 179 (2006), in press
Page 42
A3n+3m
A’n
B3m+n
O9m+6n
: intergrowth
of n[A3
O9
] and m[A3
A’O6
] triple layersCreates
B octahedral
sites and trigonal prism
sites (A’)
For A’=B=Co and n=1, m=0 Ca3 Co2 O6
1:1 CoO6
trigonal prism
and octahedron
Geometric
frustration : hexagonal
a = b = 9.13 Å
c = 10.58 Åinterchain
distance : 5.24 Å
intrachain
distance : 2.6 Åspace group R3 cK.E. Stitzer et al, Curr. Opin. Solid State Mater. Sci. 5, 535 (2001)
H. Fjellvag et al , J. Solid State Chem. 124, 10 (1996)
Page 43
0 50 100 150 200 250 300 350 4000,0
5,0x10-3
1,0x10-2
1,5x10-2
TC
0.3 Tzfc
SrCoO3
χ (e
mu.
g-1)
T (K)
SrCoO3
: edge-shared
Co4+O6
octahedrain the Pm3m cubic
perovskite
(a=0.3836 nm)Ferromagnet
with
TC = 280 K , Co4+-O-Co4+
180°
exchange
P. Bezdicka et al, Z. Anorg. Allg. Chem. 619, 7 (1993)
Page 44
SrCoO3
: edge-shared
Co4+O6
octahedrain the Pm3m cubic
perovskite
-6 -4 -2 0 2 4 6-2,0
-1,5
-1,0
-0,5
0,0
0,5
1,0
1,5
2,0
T = 2 K
SrCoO3
M (µ
B/f.u
.)
μ0H(T)
Conventional
ferromagnet
MS
= 1.75 μB
/Co
Co4+
is
neither
100%
LS or HS
Page 45
0 50 100 150 200 250 300 350
0,02
0,04
0,06
0,08
0,10
0,12
0,14
ZFC
FC 0.3 T2H-BaCoO3
χ
(em
u.m
ol-1)
T (K)
2H-BaCo+4O3 : weak
ferromagnetism
below
TC
= 50 K ?effect
of the 1D character
of the Co-O array
Page 46
00,0
0 100 200 3000,0
0,2
0,4
0,6
0,8
1,0
1,2
TC
µ0h
ac = 10-3 T
χ'' (
emu/
mol
)
T (K)
12H-Ba0.9
Co+3.2O2.6 : ferromagnetism
below
TC
= 50 K
0 50 100 150 200 250 300 3500
1
2
zfc
fc 12H-BaCoO3-δ
χ (e
mu.
mol
-1)
T (K)
Magnetic
susceptibility
values 10 times larger
than
in the 2H
Page 47
1,0
1,5
2,0
2,5
3,0
0 100 200 300 400100
101
102
103
104
105
106
ρ (Ω
.cm
)
(7T)(0T)
T (K)
ρ H=0
T / ρ
H=7
T
0 2 4 6 8-60
-50
-40
-30
-20
-10
0
100 K
% M
R 40 K
200 K
75 K
125 K
50 K
μ0H (T)
12H-Ba0.9
Co+3.2O2.6 : negative
magnetoresistance
at
TC
= 50 K
Bump
in the ρ(T) curve
at
TC -60% at
50K in 7 T
No MR measured
in the 2H : related
to the ferromagnetism
of the 12H
spin/charge interplay
Large H dependence
at
TC
Page 48
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
-0,15
-0,10
-0,05
0,00
0,05
0,10
0,15 2H - BaCoO3
T = 20 K
T = 50 K
T = 2.5 K
T = 10 KT = 5 K
M (μ
B/f.u
.)
µ0H (T)
-6 -4 -2 0 2 4 6-6
-4
-2
0
2
4
6
μ0H(T)
T = 2 K
M (e
mu.
g-1)
2H-BaCo+4O3 : weak
ferromagnetismbelow
TC
= 50 K ?
M5T
= 0.15 mB
/Co at 2.5 K μo
Hc
~ 0.8T at 2.5 K
At
2K no special
change
Page 49
-6 -4 -2 0 2 4 6
-30
-20
-10
0
10
20
30 T = 2 K
M (e
mu.
g-1)
μ0(T)
12H-Ba0.9
Co+3.2O2.6 : ferromagnetismbelow
TC
= 50 K
-6 -4 -2 0 2 4 6-1,2-1,0-0,8-0,6-0,4-0,20,00,20,40,60,81,01,2
10 K
5 K2.5 K
50 K
M (µ
B/f.u
.)
µ0H (T)
M5T
= 1.2 μB
/Co and μ0
Hc
~ 1T at 2.5 K
At
2K, additional
M jumps
Similar
to the 5H
Page 50
-6 -4 -2 0 2 4 6
-30
-20
-10
0
10
20
30
H = 250 Oe / sec
H = 10 Oe / sec
H = 110 Oe / sec
T = 2 K
M (e
mu.
g-1)
μ0H(T)
12H-Ba0.9
Co+3.2O2.6 : M jumps
at
2 K
Varying
the H sweep
rate or the waiting
timedoes
not suppress
the steps
0,0 0,5 1,0 1,5 2,0 2,50
5
10
15
20
/0.1T 60 sec
/0.25T 60 sec
T = 2 K
M (e
mu.
g-1)
μ0H(T)
Page 51
χ(a.
u.)
TC2
TC1
T(K)0 10 20 30 40 50 60 70
0,0
0,1
0,2
0,3
0,4
0,5
0,6
10-3T
Ca3
Co2
O6 single crystals
A. Maignan et al., EPJB 15, 657 (2000)
TN
TB
fc
zfc
0 5 10 15 20 25
0 5 10 15 20 25
0.000
0.002
0.004
0.006
0.008
χ''(e
mu.
g-1)
hac=3 OeCa3Co2O6 (crystal, H//chains)
104
103
102101
10-1
100
10-2Hz
T(K)For f>1 Hz, T(χ’’max
) increasesas in a superparamagnet
But f <1Hz, fixed T(χ’’max
)
1 cmA3n+3m
A’n
B3m+n
O9m+6n
: A’=B=Co and n=1, m=0 Ca3 Co2 O6
Page 52
MagnetismCa3
Co2
O6
c
J > 0
Ferro IntrachainCoupling
AntiFerro
Interchain
CouplingJ’ < 0
“
1 D + Frustration “
c
+
_
?
intrachain
: ferro
(F)interchain
: antiferro
(AF)
TN
= 25K
S = 0 → Octahedron S = 2 → Trigonal
Prism
Co3+
Decrease of the AF peak intensity below ∼
15K !Loss of the magnetic coherence along the chain ?
isolated finite spin units ?S. Aasland et al, Solid State Comm. 1997, 101, 197.
Strong
local anisotropy
(TP)
Page 53
XMCD on crystals
: TP S=2, Oct. S=0large orbital moment 1.7 μB
Consistent with
the special
crystal
field
splittingin the Trig. Prism
: orbital d2
Predicts
large orbital moment :exp. Ms (10K) > 4 μB
Responsible
for the strong
magnetic
anisotropyL. H. Tjeng et al, Köln University
Page 54
0 1 2 3 4 5 6 7 8 90
1
2
3
4
5
T = 2 K
M (μ
Β /
f.u.)
μ0H(T)
0 1 2 3 4 5 6 7
0.1
1
10 T = 2 K1.2 T
2.4 T3.6 T
7.1 T5.9 T
4.7 T
dM/d
H (a
.u.)
μ0Η(Τ)
c H
A. Maignan et al, J. of Mater. Chem. 14, 1231(2004)
Ca3
Co2
O6
QTM
n=1, m=0
Page 55
Ca3
Co2
O6
–
magnetization stepsIsing triangular TN
=24K
0 1 2 3 4 5 60
1
2
3
4
5
T=10K
M (μ
B/f.u
.)
μ0H(T) 0 2 4 6 8 100
1
2
3
4
5
T=2K
M (μ
B/f.u
.)
μ0H(T)
ΔH=3.6T
ΔH=1.2TFI →
FO
0 25 50 75 100 125 150 175 2000
2
4
6
8
10
12 TN
CM (J
K -1
mol
-1)
T(K)
Page 56
Ca3
Co2
O6
–magnetodielectric coupling
0 1 2 3 4 5 60
1
2
3
4
5
M (μ
B/f.u
.)
0 1 2 3 4 5 6
-1
0
Δε H
/εsa
t (%
)
μ0H(T)
T=10K
0 1 2 3 4 5 6-3
-2
-1
0
ΔεH/ε
sat(%
)
μ0H(T)
T=4K
0
1
2
3
4
5
M (μ
B/f.u
.)
0 1 2 3 4 5 60.00.20.40.60.81.01.2
χ(μ B/T
·f.u.
)
0 0
0.5
1.0
1.5
χ(μ B/
T·f.u
.)
Δε∼-χBellido N, Simon C, Maignan A. , Phys. Rev. B 77, 054430 (2008)
Page 57
Plan:
3D magnetic
networks:CMR in perovskite
manganites
MIT in cobaltitesFrustrated
lattices
of the «
114
»
type
1D and 2D TM-O-TM
networks: hexagonal perovskitesand CdI2
type structures
n-type vs p-type
conductivity
in oxides
Page 58
2 ceramic
substrates
that
serve as thermal link
and electrical
insulation
of p-type and n-type diceDices
connected
electrically
in series
and thermally
in parallelSolder at
the connection
joints to ensure
the electrical
connections and hold
the module together
How a TE Generator
Works ?
Page 59
Figure of merit
Power factor
ρκ=
2SZ
ρ=
2SPF
For applications : n and p type materials
withZT > 1
Current
Electricity
generation
p n
Heater
Heat
sink
ΔV ΔT⇔
Seebeck effect
(ΔT ΔV) : thermogeneratorsPeltier effect
(ΔV ΔT) : cooling
systems
⇒⇒
THot
TCold
S=ΔV/ΔT
c
hm
mCarnot
c
hm
m
h
chmax
TTZT1
1ZT1
TTZT1
1ZT1T
TT
++
−+η=
++
−+−=η
Efficiency
of a thermogenerator
Thermoelectric Generators (TEG)
Page 60
Module under
test
Page 61
Te/
TeS/S
S)1()2( μ
→μ+−
=
Limit T →∝ : S ~ entropy / carrier
for T →∝
)x
x1ln(e
kS B −−=
Narrow
band systems
with
strong
interactions : the Hubbard model
+ Spin and/or orbital degeneracy
β )xx-1ln(
ekS B β−=
p typeNax
CoO2
I. Terasaki
Misfit cobaltites
T-independentNot expected
for metal
Page 62
(Bi0.87 SrO2 )2 (CoO2 )1.82 oxide
Sous réseau 1 [(Bi0.87
SrO2
)2
] : a = 4.90 Å, b1 = 5.11 Å, c = 29.86Å, β
= 93.4°Sous réseau 2 [CoO2
] : a = 4.90 Å, b2 = 2.81 Å, c = 29.86Å, β
= 93.4°b1 /
b2 = 1.82≈
11/6
N = 4
H. Leligny et al,C.R. Acad. Sci. Paris, t.2Série IIc, 409 (1999)
Co network: triangles
Page 63
Origin
of large S?
Spin and Orbital DegeneracyCo3+
(3d6)/Co4+
(3d5)
LS states due to CdI2 layers
)x1
xggln(
ekS
4
3B
−−=
Localized
picture
: the generalized
Heikes
formula
Maekawa
and cowork. Phys. Rev. B 62, 6869 (2000)
Band structure calculations
:Lifting of the t2g
levels
degeneracy
due to rhombohedral
crystalline
field
of
CdI2
layers
FEE
22
))ln((e3k
TS
==dE
d σπ
D. J. Singh, Phys. Rev. B 61, 13397 (2000)T. Yamamoto et al., Phys. Rev. B 65, 184434 (2002)
Peak
in DOS : large S+ MetallicityAt
high
T
:
Page 64
Scaling
MR et MTEPLien avec la susceptibilité
MagnetothermopowerMisfit
BiCaCoO
Similar
to Na0.7
CoO2Y. Wang et al., Nature423, 425 (2003)
Scaling
law
for S(H) : paramagnetic
spins S=1/2Brillouin function
P. Limelette et al., PRL97, 046601 (2006)
Decrease
of S in field
at
low
TDue to the alignement of paramagnetic
spins
Peak of susceptibility
NMR
J. Bobroff et al,PRB (LPS Orsay)
Page 65
0 50 100 150 200 250 3000
20
40
60
80
100
S (μ
V.K-1
)
T (K)
Bi1.95Ba1.95Rh1.9Oα
Bi2Ba2Co2Oα
0 100 200 300 4000
5
10
15
20
MR
(%)
ρ (m
Ω.c
m)
T(K)
0 10 20 30 40 50
-2
0
2
4
6 14T 7T 3.5T
[Bi1.95
Ba1.95
Rh0.1
O4
][RhO2
]1.8
Metallic
down to 50KLarge S
: spin degeneracy
β
= 1/6
Small and positive magneto-resistance
Y. Klein, Phys. Rev. B 73, (2006) 165121
T-independentMetallic
Page 66
SrRuO3Chemical formula Calculated Ru
oxidation state
SrRuO3 4SrRu0.97
O2.94 4SrRu0.92
O3 4.35SrRu0.975
Cr0.025
O3 4 (for Cr4+)SrRu0.9
Mn0.1
O3 4.11 (for Mn3+)Sr0.8
La0.2
RuO3 3.80
0 50 100 150 2000
10
20
Sr0.8La0.2RuO3
SrRu0.92O3 SrRu0.97O2.94
SrRuO3
SrRu0.975Cr0.025O3
SrRu0.9Mn0.1O3
dc, FC, 1 kOe
M (e
mu/
g)
T (K)
0 50 100 150 200 250 300 350 400
10-3
10-2
SrRuO3
SrRu0.92O3
Sr0.8La0.2RuO3
SrRu0.97O2.94
SrRu0.975Cr0.025O3
SrRu0.9Mn0.1O3
T (K)
ρ (Ω
cm)
Page 67
0 200 400 600 8000
5
10
15
20
25
30
35
40
Sr2RuO4
CaRu0.8Ga0.2O3
CaRuO3
SrRuO3
S (μ
V.K-1
)
T (K)
Ruthenates: same
behavior
for S(T)
Spin only
contribution, works
in a metallic
compound
Ru3+
/Ru4+
1121)2/1(2
+×+×
=β
Sspin
= 35μV/K
Ru4+
/Ru5+
Sspin
= 25μV/K
Page 68
0 100 200 300 400 500 600 700 800 900-202468
10121416182022242628303234
La0.5Ca0.5Cu3Ru4O12 LaCu3Ru4O12
S (µ
V.K-1
)
T (K)
0 100 200 300 400 500 600 700 800 9000,0
1,0x10-42,0x10-43,0x10-44,0x10-45,0x10-46,0x10-47,0x10-48,0x10-49,0x10-41,0x10-31,1x10-31,2x10-31,3x10-31,4x10-31,5x10-3
LaCu3Ru4O12
ρ (Ω
.cm
)
T (K)
ACu3
Ru4
O12Large mass enhancement(γ=135mJ/fu.mol.K2 for A=La)ex: RuO2
γ=6mJ/fu.mol.K2S. Tanaka et al, cond-mat 28 june 2009
A. Maignan et al (to be published)
T lineardependence
T lineardependence
Page 69
Plan:
3D magnetic
networks:CMR in perovskite
manganites
MIT in cobaltitesFrustrated
lattices
of the «
114
»
type
1D and 2D TM-O-TM
networks: hexagonal perovskitesand CdI2
type structures
n-type vs p-type
conductivity
in oxides
Page 70
AMO2
A (dumbell)
MO22H or 3R depending
on
oxygen
packing
PdCoO2
: metal, like
PdDJ Singh
Doped
CuCrO2
: bad
metalwith
large S
Du Pont 1970
Delafossite: layer compound with CdI2 type layer
M network: triangles
Page 71
0 50 100 150 200 250 300 350 4000,0
1,0x10-5
2,0x10-5
3,0x10-5
4,0x10-5
5,0x10-5
6,0x10-5
7,0x10-5
8,0x10-5
9,0x10-5
TN
CuRh0.9Mg0.1O2
CuCr0.98Mg0.02O2
ZFC, 0.3 T
χ (e
mu.
g-1)
T (K)
CuCr1-x
Mgx
O2 CuRh1-x
Mgx
O2
Triangular
AF S=3/2Pauli paramagnet
S=0
Page 72
CuRh1-x
Mgx
O2
For large enough
hole
contentmetal-like
behavior
as cobaltites
Experiment
Calculated
SαT
Page 73
PF is
rather
T independent
CuRh1-x
Mgx
O2
300 400 500 600 700 800 900 1000 1100100120140160180200220240260280300320340
x=0.00
x=0.01 x=0.04
x=0.10
S (µ
V.K-1
)
T (K)
300 400 500 600 700 800 900 1000 11000,0
5,0x10-51,0x10-41,5x10-42,0x10-42,5x10-43,0x10-43,5x10-44,0x10-44,5x10-45,0x10-45,5x10-46,0x10-46,5x10-47,0x10-47,5x10-4
x=0.00
x=0.01
x=0.04
x=0.10
S2 ρ-1 (W
.K-2.m
-1)
T (K)
Large T range for Fermi liquid-like
behavior
Page 74
Spiral magnets
Spiral magnets breaking inversion symmetry, in an insulator, induces a polarization.
Spin rotation axis
Wave vector of the spiral≠][ QePrrr
×≈
Mostovoy Phys.Rev.Lett.96 067601 (2006)
M. Kenzelmann Phys. Rev. Lett. 95, 087206 (2005)
CFE TT = Ferroelectricity
is induced by magnetic order
Peak in dielectric constant
5 10 15
4.02
4.03
4.04
Ni3V2O8
ε
T(K)
Page 75
Modulated
antiferromagnetic
structures found
in geometrically frustrated insulating materials
Spin current
model
Page 76
Antiferromagnetically
stacked
proper
helical
structure (q,q,3/2), q=0.21
][ QePrrr
×≈
BUTe//Q (on average) , P=0
Spin current
model
Crystals
to test for the chirality
Spin current
model
New explanation
is
requiredin doped
CuFeO2
c is
the spin chirality
vector
Page 77
0 50 100 150 200 250 300 350 40010-1
100
101
102
103
104
105
x = 0.06
x = 0.03
x = 0.01
x = 0.005
x = 0.02
x = 0.00
ρ (Ω
.cm
)
T (K)0 50 100 150 200 250 300
0
200
400
600
800
1000
1200
x = 0.005
x = 0.01x = 0.03
x = 0.04
CuCr1-xMgxO2
x = 0.00
x = 0.06
x = 0.02
S (µ
V.K-1
)
T (K)
Transport properties
of CuCr1-x
Mgx
O2
Large resistivity
drop up tox=0.02
Large S drop up tox=0.02
Holes
: Cr4+
Activated
(x=0.00) to small
polaron
(x>0.01)
Maekawa
TEM/ED/EDX/XRD: xmax
=0.01
Trivalent Cr S=3/2
Page 78
T (K)0 50 100 150 200 250 300
1/χ
(mol
.em
u-1)
160
180
200
220
240
260
280
μeff = 3.89μΒ
CW = -202K
T (K)5 10 15 20 25 30 35 40
χ (em
u.g-1
)
41x10-6
42x10-6
43x10-6
44x10-6
TN
CuCrO2
SG: R-3m
NTE
No structural transitionKeeps
a centrosymmetric
structure
Undoped: insulator
Trivalent Cr S=3/2
Page 79
CuCrO2
M. Poienar et al, Phys. Rev. B 79, 014412 (2009)
10-1
100
101
102
103
104
105
0 50 100 150 200 250 300 350
0 25 50 75 1000.000
0.025
0.050
0.075
0.100
0 10 20 30 40 500
5
10
15
20
x = 0 x = 0.02
C (J
.K-1.m
ol-1)
T (K)
CuCr1-xMgxO2
T (K)
ρ (Ω
.cm
)
C/T
(J.K
-2.m
ol-1
)
T2 (K2)
K. Kimura et al, Phys. Rev. B 78, 140401R 2008exp: in-plane polarization
AF, incommensurate propagation vector k = (q, q, 0) with q ≅
0.329(1)
Helicoidal
AF
Page 80
-10 -5 0 5 10
14
16
18
20
25-25
-20
-15
-10
-5
0
5
10
15
20
25Po
lariz
atio
n(Δ
P(μC
/m2 ))
μ0H(T)
Related
to structural changes
0 5 10 15 20 25T(K)
CuCrO2
TN
Page 81
Cr [3a (0,0,0)]
Ag [3a (0,0,0.1549(2))]S1
[3a (0,0,0.2691(3))]
S2
[3a (0,0,0.7307(3))]
AgS4
“tetrahedra”
CrS6“octahedra”
a = 3.4961(1)Å
c = 20.5316(5)Å
AgCrS2S O
acentric
R3m rhombohedral
Two sets of three Cr-S interatomic
distances (about 2.386 Å
and 2.447 Å)Different from the 6 equivalent Cr-O distances of delafossites
Page 82
0
100
200
300
400
0 50 100 150 200 250 300 350 4000,002
0,004
0,006
0,008
0,010
0,012
0,014
0 10 20 30 40 50 60 70 80102
103
TN
CuCrS2
ρ (Ω
.cm
)
T (K)
AgCrS2
CuCrS2
AgCrS2
CuCrS2
χ-1 (m
ol.e
mu-1
)
χ (e
mu.
mol
-1)
T (K)
5,05
5,10
5,15
5,20
40
60
80
100
(a)
ε'
0 5 10 15 20 25 30 35 40 45 50 55 60-25
-20
-15
-10
-5
0
5
10
15
20
0 5 10 1513.0
13.5
14.0
14.5
15.0
P(μ
C/m
2 )
B(T)
(b)
ΔP (μ
C/m
2 )
T(K)
χ (μ
emu.
g-1)
K. Singh et al, Chem. Mater. 2009, 21 (21), pp 5007–5009
AgCrS2
AF insulator
Page 83
JT-cation: CuMnO2
JT distortion
lifts the eg
orbital degeneracyOrbital ordering
crednerite
C2/m
NaMnO2M. Jansen and R. Hoppe, Zeitschrift Fur Anorganische Und Allgemeine Chemie 399, 163 (1973)S=2
a = 5.5945(2)Å, b = 2.8847(1)Å, c = 5.8935(2)Å
and b = 103.97(2)°
Page 84
propagation vector k1 = (-½
½
½)
F. Damay et al , Phys. Rev. B 80, 094410 (2009)
TN
=65K
monoclinic (C2/m) to strained triclinic C 1
Anisotropic
magnetic
in-plane
interactions
No magnetoelectric
properties
Page 85
Plan:
3D magnetic
networks:CMR in perovskite
manganites
MIT in cobaltitesFrustrated
lattices
of the «
114
»
type
1D and 2D TM-O-TM
networks: hexagonal perovskitesand CdI2
type structures
n-type vs p-type
conductivity
in oxides
Page 86
T)(
STSZTle
22
κ+κρ=
ρκ=
Degenerate
semiconductors
, best TE
n type
Page 87
TCO physics:
Zn1-x
Alx
O (x = 0 –
0.1)ZT = 0.6
M. Ohtaki et al
Page 88
0 200 400 600 800 1000
1,0x10-2
2,0x10-2
3,0x10-2
4,0x10-2
5,0x10-2
6,0x10-2
7,0x10-2
0.0075 0.005
0.0025
0.03
0.01
ρ (Ω
.cm
)T (K)
ρ
minimum for x=0.01
Zn1-x
Alx
O
Proceedings
ICT 2008
Page 89
Zn1-x
Alx
O
300 400 500 600 700 800 900 1000 1100-230-220-210-200-190-180-170-160-150-140-130-120-110
0.0075
0.005
0.0025
0.03
0.02
0.01
S (µ
V.K-1
)
T (K)|S|
minimum for x=0.01
FEE
2B
2
)E
)E(ln(T3ek
S =∂∂
=σπ
Not able to reproduce
Page 90
Pb1.6
V8
O16 1D structure
I12/m1 space group with a=10.125Å, b=2.902Å
and c=9.880Å
1.4e-
in the V empty t2g
orbitalsn type?
Hollandite
Page 91
300 400 500 600 700 800 9002,0x10-5
3,0x10-5
4,0x10-5
5,0x10-5
6,0x10-5
7,0x10-5
8,0x10-5
9,0x10-5
S2 ρ-1 (V
2 .K-2.Ω
-1.m
-1)
T (K)
1,0x104
2,0x104
3,0x104
4,0x104
5,0x104
6,0x104
7,0x104
8,0x104
9,0x104
1,0x105
1,1x105
1,2x105
1,3x105
0 50 100 150 200 250 300 350 4000,0
1,0x10-5
2,0x10-5
3,0x10-5
4,0x10-5
5,0x10-5
6,0x10-5
7,0x10-5
8,0x10-5
100 110 120 130 140 150 160 170 180 190 2009,00x10-6
9,20x10-6
9,40x10-6
9,60x10-6
9,80x10-6
1,00x10-5
1,02x10-5
1,04x10-5
fcc fcw
χ (e
mu.
g-1)
T (K)
fccfcw
fcw
χ (e
mu.
g-1)
T (K)
χ -1 (g
.em
u-1)
10-3
10-2
10-1
100
101
102
103
104
105
106
0 100 200 300 400 500 600 700 800 900-45
-40
-35
-30
-25
-20
-15
-10
-5
ρ (Ω
.cm
)
S (µ
V.K-1
)
T (K)
TN
TN
Pb1.6
V8
O16
1.7 mΩ.cm to 2.2 mΩ.cm
300K 100K
From
ED:no struct.transition
n type!
Page 92
a1a2
c
V2
O9
dimmers
Pb
V in VO5trigonal bipyramid
a
c
a b
VO6
octahedra
layer
PbV6
O11
5/3 e-
in the V empty t2g
orbitals
kagome
RT : 5.7567(1) Å
and 13.2662(2) ÅP63
mc
Page 93
-8 -6 -4 -2 0 2 4 6 80,70
0,75
0,80
0,85
0,90
0,95
1,00
-4 -3 -2 -1 0 1 2 3 40.86
0.88
0.90
0.92
0.94
0.96
0.98
1.00
1.02 20 K
ρ(H
) / ρ
(H =
0)
µ0H (T)
200 K150 K
120 K
100 K
90K40K60K
20K
PbV6O11
ρ(H
) / ρ
(H =
0)
µ0H (T)
-8 -6 -4 -2 0 2 4 6 8-18-15-12-9-6-30369
121518
120K 90K 60K 20K
PbV6O11
M (e
mu.
g-1)
µ0H (T)
PbV6
O11
SPINTRONIC
A.Maignan et al, APL (in press)
Ferro. Like
component
Page 94
0,0010 0,0015 0,0020 0,0025 0,0030
-20-18-16-14-12-10-8-6-4-202468101214
300 400 500 600 700 800 900-20-18-16-14-12-10-8-6-4-202468
101214
S (µ
V.K-1
)
T -1 (K-1)
S (µ
V.K-1
)
T (K)
0 100 200 300 400 500 600 700 800 90010-2
10-1
100
101
102
103
104
105
106
0,000 0,005 0,010 0,015 0,02010-2
10-1
100
101
102
103
ρ (Ω
.cm
)
T -1 (K)
ρ (Ω
.cm
)
T (K)
0 50 100 150 200 250 300 350 4000,0
5,0x10-31,0x10-21,5x10-22,0x10-22,5x10-23,0x10-23,5x10-24,0x10-24,5x10-25,0x10-25,5x10-26,0x10-26,5x10-2
fc
zfc
χ (e
mu.
g-1)
T (K)
TC
TC P63/mmcP63mc
PbV6
O11
Structural transitionFrustration is
lifted
n type
Page 95
Conclusions :
Many
things
still
to be
discovered
in oxides
!!!!!!!!!!!
Decreasing
the thermal conductivity
: polyanions
?
Electronic
correlations, spin/charge/orbital coupling
Page 96
Thanks
to my
Colleagues
Christine Martin, Denis Pelloquin, Sylvie HébertRaymond Frésard, Oleg Lebedev, Charles Simon,Vincent Caignaert, Valérie Pralong, Bernard Raveau
andLPS, UJF, IPCMS, ICMCBLLB, ILL, ISIS, MPI Dresden, Koeln
and Augsburg
Univ. ,
NIU
and
Post-docs, PhDs