International Symposium on Present and Future of Material Sciences Osaka university 17-18 november 2015

Solid State chemistry of electron correlated oxides: From perovskite derivatives to triangular metallic lattices Bernard Raveau Laboratoire CRISMAT, UMR 6508 CNRS-ENSICAEN, Univ .of Caen, France

Electron correlated systems :transition metal oxides

Multiple transitions: structural, electrical,magnetic

Cuprates: high Tc superconductivity Manganites: Colossal MagnetoResistance CMR Cobaltates : high t° thermoelectricity Ferrates : multiferroicity

New Transition Metal Oxides for New Properties

TM

valence

A: countercation TM

coordination

Oxygen stoichiometry

Transport, dielectric

Magnetic properties

Structure

La4BaCu5O13

non supercond La2-xBaxCuO4 La2-xSrxCu2O6 YBa2Cu3O7

supercond. supercond. supercond.

- mixed valence Cu2+/ Cu3+

- 2D-Structure : Jahn-Teller effect of copper - Apical/equatorial oxygen O- : Cu3+ 3d8 Cu 2+ 3d9L

3D

superconducting copper oxides

Maeda & al (1988) Takano & al (1988) Borel &al (1987 )

Bi2Sr2CuO6+δ

Superconductivity up to 110 K

Bi2Sr2CaCu2O8+δ Bi2Sr2Ca2Cu3O10+δ

Colossal Magnéto-Resistance Perovskites : Ln1-x (Ca,Sr)xMnO3

Transition paramagnetic insulator ferromagnetic metal

- mixed valence Mn3+/Mn4+ : double exchange (« metal ») - Jahn-Teller effect of Mn3+: control of structural distortion

AFM insulator FM metal charge ordering charge delocalisation Mn3+ and Mn4+ mixed valence J-T effect of Mn3+ Mn3+/Mn4+

Réalisation doping - On Mn3+ sites : Ga3+, Cr3+

or on Ca2+ sites: Ba2+

structural transition

Colossal Magneto-Resistance Perovskites : Pr0.5Ca0.5MnO3

Thermoelectric cobalt oxides :« misfit »

(Bi0.87SrO2)2(CoO2)1.82

-mixed valence Co3+/Co4+

- 2D-structure - triangular cobalt lattice

- p-type semi-metal - High TEP : ~140 µVK-1 - low thermal conductivity

Oxygen Deficient Double Perovskites : LnBaCo2O5.5+δ

-mixed valence: Co2+/Co3+ (-0.5<d<0) Co3+/Co4+ (0<d<+0.5) - Charge order and delocalisation - disproportionation: 2Co3+=Co4+ +Co2+

Numerous magnetic transitions e.g. metal-insulator , PM-AFM transition, high magneto-résistance

Swedenborgite:the « 114 family »

Valldor & al Solid State Sci.4,923(2002)

YBaCoII3CoIII O7

Geometric frustration

Spin glass :Tf =66 K

Antiferromagnet: TN = 110 K

Mixed valence in a tetrahedral system

Kagome layers & triangular layers

Changing the cobalt mixed valence

into Co2IICo2

III instead of Co3II Co1

III

CaBaCo4O7

Trigonal aH, cH orthorhombic aOaHV3, b~bH, c~cH

Charge ordering (BVS)

Co2, Co3 (K layers) :Co2+

Co1(T layers), Co4(K layers) :Co2+/Co3+

Co3+ =Co3d6 Co2+ = Co3d7L

V..Caignaert et al. Phys.Rev. B 2010

Lifting of the geometric frustration

Noncentro :Pbn21( polar axis :c)

CaBaCo4O7: Ferrimagnet TC= 64 K

Magnetic Structure of CaBaCO4O7

FM Co2+ zig zag chains // to b AFM coupled with co3+ and Co2+L

CaBaCo4O7: dielectric permittivity & loss vs T at 100 kHz.The coincidence of the

peaks and TC evidences the spin and charge coupling.

K.Singh et al Phys. Rev. B 86, 024410 (2012)

CaBaCo4O7: Electric polarization vs T showing a transition around TC and

sign change of P by reversing E, suggesting spin driven ferroelectricity.

CaBaCo4O7: Magnetodielectric effect vs magnetic field at different t°.

E and H are perpendicular to each other.

sharp transition along b @TC=64 K

(100 Oe)

Sharp transition along c @ TC=64 K

(100 kHz)

CaBaCo4O7 : magnetoelectric coupling along c

Specific heat: 0Tblue, 1Tgreen, 2T red

Gigantic variation of the polarisation

along c: ΔP=17mC/m2 @ 10K (Ec=1.1 kV/cm)

But cannot be reversed completely by

changing the polarity of E(14kV/cm)

Caignaert et al PRB 88, 174403 (2013)

Polarisation along polar axis c, with H along b

Large increase of the polarisation

with the applied magnetic field

Magnetoelect. coeff α32 and β322

Largest ME effects are close TC

Caignaert et al PRB 88, 174403 (2013)

Research of mixed valent Fe(II)- Fe(III) oxides

Trigonal YBaCo4O7 Spinel Fe3O4

Co(II)-Co(III) Fe(II)-Fe(III)

kagome tetrahedral layers kagome octahedral layers

triangular tetrahedral layers triangular tetrahedral layers

frustrated magnetic structure ferrimagnet

complex magnetic transitions complex charge ordering

« 114 » oxides : CaBaFe4O7 & YBaFe4O7

B.Raveau & al Chem .Mater. V.Caignaert & al chem Mater. 21,1116 (2009)

20, 6295 (2008)

Fe

1

Fe

2

Trigonal CaBaFe4O7

B.Raveau & al Chem .Mater. 20, 6295 (2008)

0 50 100 150 200 250 300 350 400

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

Zfc

Fc H = 0.3 T

M (

µB/f

.u.)

T (K)

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

-3.0

-1.5

0.0

1.5

3.0

-3.0

-1.5

0.0

1.5

3.0

-3.0

-1.5

0.0

1.5

3.0

-3.0

-1.5

0.0

1.5

3.0

5K

M (

µb/f

u)

Field (T)

50K

150K

250K

CaBaFe2IIFe2

IIIO7

Mexp =3mB / f.u.

Fe(II) : HS (tetrahedral) eg3 t2g

3

Fe(III) : HS (tetrahedral) eg2 t2g

3

ferromagnetism : Mth=18mB/f.u.

Ferrimagnetic : AFM coupling between kagome & triangular layers

Geometric frustration +charge ordering ?

Investigation of Y-Ba-Fe-O system YBaFe4O7 cubic instead of trigonal

ac= 8.9 A ~ aH 2

1/2 similarity with spinel But Fe in tetrahedra only!

(111)C layers in YBaFe4O7

Kagome

(001)H layers in CaBaFe4O7

YBaFe4O7 CaBaFe4O7

Kagome & Triangular Layers of FeO4 Tetrahedra

Triangular Tunnels obstructed by YO6 Octahedra

YBaFe4O7 :

View along <110>C

CaBaFe4O7 :

View along <100>H

V.Caignaert & al Chem. Mater. 21, 1116 (2009)

0 50 100 150 2007,0x10

-5

8,0x10-5

9,0x10-5

1,0x10-4

1,1x10-4

1,2x10-4

1,3x10-4

1,4x10-4

1,5x10-4

1,6x10-4

1,7x10-4

1,8x10-4

0,0030 0,0035 0,0040 0,0045 0,0050 0,0055 0,0060 0,0065 0,0070

102

103

104

105

(

.c

m)

1/T (K-1)

30 40 50 60 701.5x10

-4

1.6x10-4

1.6x10-4

1.7x10-4

1.7x10-4

1.8x10-4

1.8x10-4

1.9x10-4

1000Hz

10000Hz

' (e

mu

.g-1)

T (K)

1000Hz

10000Hz

' (

em

u.g

-1)

T (K)

Spin glass like behavior of YBaFe4O7

V.CAIGNAERT & al Chem. Mater. 21,1116 (2009)

0 50 100 150 200 250 300

0.010

0.015

0.020

0 100 200 300

0.000

0.001

0.002

ZFC

FC

M (

mB/f

.u.)

Temperature (K) Fig. 1M

FC-M

ZF

C (

mB/f

.u.)

T (K)

mixed valence iron oxides: Fe3+/Fe4+ ? Perovskites Ln2Ba3Fe5O15-δ

Sm0.4Ba0.6FeO3-x: cubic Short range AFM interactions from PXRD under low field Tapez une équation ici.

Nanoscale Ordered Quintuple perovskite Ln2Ba3Fe5O15- δ

HRTEM : Tetragonal « 5ap »:

Semi ordered distribution of Sm/Ba layers

Sequence: Sm-(Ba/Sm)4-Sm ?

Ln2Ba3Fe5O15-δ

High angle annular dark field STEM

HAADF-STEM

I~ Z2: Z=56 for Ba , Z=62 for Sm

Layered ordering is:

« Sm-Ba-Sm/Ba-Sm/Ba-Ba-Sm »

Ln2Ba3Fe5O15-δ :EELS elemental mapping

HAADF Fe Sm Ba O-K colour

Sm

Ba

Sm/Ba

Sm/Ba

Ba

Sm

Schematic representation of quintuple perovskite structure of

Ln2Ba3Fe5O15-δ represented as intergrowth of

double and triple perovskite structures.

EELS fine structure of Sm2-εBa3+εFe5O15-δ; (Left panel) O-K edge fine

structure signatures from the regions indicated in the central panel.

Structural model with indicated EELS integration areas. (Right panel) Fe-L2,3

fine structure signatures from the regions indicated in the central panel with

references for 4, 5 and 6-fold coordinated Fe3+, and a simultaneously acquired

and energy-shifted Ba M5 edge.

O vacancies in the median layers

Fe3+/Fe4+ mixed valence

Fe3+3d5 Fe3+3d5 L

Ln2Ba3Fe5O15-δ: Nanoscale chemical twinning

HRTEM

HAADF-STEM Hinders long range AFM ordering

Key Factors: Impact on Physics

TM valence: single, mixed, charge ordering, possible transitions vs T « A » Counter Cation: influences the structure (size) and TM valence (acido-basic: bond competition) TM coordination: Tetrahedral, octahedral, pyramidal,square influences structure, crystal field and chemical bonding Oxygen issue : stoichiometry, order- disorder of vacancies, influences TM valence and coordination, influences structure, issue of charge (O2- or O-) Structure : geometry of the lattice («square » or « triangular »),cationic & anionic order-disorder, struct. distortions, dimensionality, centro or non-centro symmetry, commensurability (or non)

Aknowledgements

V. Caignaert (Caen) S. Turner ( Antwerp) O. Lebedev (Caen) Md. Motin Seikh (Santiniketan) V. Hardy (Caen) A. Kundu (New Dehli) N. Gauquelin (Antwerp) V. Cherepanov (Ekaterinburg)

PERSEVERANCE WORK LUCK

Interactions 3d-4f: Ba2LnFeO5 apparentés aux pérovskites

Ba2YFeO5: AFM, TN=5.1 K Super-super échange Fe-O-O-Fe: J5

10

20

0

10

20

30

0

10

20

30

0 2 4 6 8 10 12 14

5

10

0 5 10 15 20 25 300

10

20

30

10

20

4

8

12

10

20(c) Gd

Cp (J

K-1 m

ol -1)

Cp (

J K

-1 m

ol-1

)

(e) Dy

(f) Ho

(d) Y

T(K)

(h) Yb

Ba2LnFeO

5(a) Sm

(b) Eu

(g) Er

0 1 2 3 4 5 6 7 8 90

2

4

6

8

10

M(m

B/f

.u.)

H(Tesla)

Ba2LnFeO

5

Sm

Eu

Gd

Dy

Ho

Y

Er

Yb

0.86 0.88 0.90 0.92 0.94 0.96

4

5

6

7

8

9

10

11

Sm

Eu

Gd

DyHo

Y

Er

Yb

ionic radius VI (A)

tran

sit

ion

tem

pera

ture

(K

) from specific heat

from magnetic data

What about the Future of Solid State Chemistry in Strongly Correlated Oxides?

Discovery of new oxides for new properties

Numerous results on nanomaterials, hybrids.

but

Chemistry of bulk materials: very few new compounds

Methods of synthesis: e.g.high pressure,

soft chemistry, electrochemistry, laser ablation in thin films

and or

Use new methods of investigation for design of new

frameworks: HRTEM, HAADF-STEM,EELS