J. Rouquette, J. Haines

from LuFe2O4.5

= CYCLES

Effect of oxygen stoichiometry on magnetic properties

E. Elkaim

k1 = (0 2/3 0)m and k2 = (0 2/3 1/2)m

hkl broadening : disordered stacking of magnetic

platelets

AFM at RT

Loss of the triangular character

of the Fe lattice

50 nm

Nanostructures in LuFe2O4+δ M. Hervieu et al. Solid State Science 23, 26 (2013)

ADAPTABILITY and FLEXIBILITY : towards new coupling types for applications ?

M -LuFe2O4

C2/m subcell

+ O

2

- O2

[001] [100] [010]

M’ -LuFe2O4.5

C2/m subcell

O supercell

+ Reversibility Without altering the quality of the material

(by Ar/H2 annealing )

Sensitivity of the oxygen uptake phenomena:

Low temperature (200°C) And low pressure

(primary vacuum)

aM

bM

cM

cR

aR

Lu

Fe

LuO6 octahedra = CdI2 type layer

FeO

5

= t

rian

gula

r b

i-p

yram

ids

Fe

Lu

[LuFe2] [LuFe2] [Fe2]

[Lu]

M - LuFe2O4 M’ - LuFe2O4.5 hp - LuFe2O4

Similarity between oxygen non stoichiometry and pressure effects

LuFe2O4+d:

from magnetism to oxygen storage

C. Martin, M. Hervieu, A. Guesdon, A. Maignan

LuFe2O4

T >

T CO

= 3

30

K :

R-3

m

Oxygen insertion

from LuFe2O4 … to LuFe2O4.5

[= 1Fe+2: 1 Fe+3]

[= 2 Fe+3]

OSC = 1 426 mmol O g-1

DV/V = +2.2%

….to LuFe2O4

Ordering inside layers

and inter-layers

M -LuFe2O4

modulated M -LuFe2O4.25

and M -LuFe2O4.286

‘’LuFe2O5’’

‘’LuFe2O4’’

M supercell R13 -LuFe2O4.318

M’ supercell

O -LuFe2O4.5

aM

bM

aM bM

aR

aR13

bM’ aM’

bO

aO

3 3 4 4 4 4 4

Rev

ersi

ble

ph

eno

men

a st

ud

ied

by

XR

, e-

and

neu

tro

n d

iffr

acti

on

, TG

A a

nd

Mo

ssb

auer

Oxygen insertion - by a progressive transition characterized by (at least)

3 metastable structures (M, R13, M’) - involving short range ordering phenomena in more or less extended domains

and shearing mechanisms. For all, the stacking of 1 Lu for 2 Fe layers is preserved.

Complex magnetism linked to the 2D triangular iron lattice: two TN (250 and 200K) and two magnetic propagation vectors → magnetic phase separation at low temperature

Lay

ered

str

uct

ure

Complex microstructure in connection with Fe2+ : Fe3+ charge ordering at ≈ 330K (modulations q = βb *+ γc *)

New modulations in the h0l plane q = αa* + γc*

Evidence of oxygen-dependent modulation in LuFe2O4. J. Bourgeois et al. Phys. Rev. B85, 064102 (2012)

Evidence of magnetic phase separation in LuFe2O4.

J. Bourgeois et al. Phys. Rev. B86, 024413 (2012)

Oxygen storage capacity and structural flexibility of LuFe2O4+x (0 ≤ x ≤ 0.5)

M. Hervieu et al. Nature Materials (2013) doi:10.1038/nmat3809

Rare earth ferrites LuFe2O4±δ: polymorphism,

polytypism and metastable phases M. Hervieu et al.

Solid State Sciences 48, A1-A16 (2015)

From LuFe2O4 to hp-Fe2O4: High pressure effect

F. Damay

Stacking of 1 Lu for 2 Fe layers and intercrossing of diagonal atomic layers preserved.

Pressure-Induced Structural Transition in LuFe2O4: Towards a New Charge Ordered State. J. Rouquette et al. Phys. Rev. Lett 105, 237203 (2010) Pressure effect on the magnetic order of LuFe2O4. O. L. Makarova et al Appl. Phys. Lett. 103, 082907 (2013) A high-pressure polymorph of LuFe2O4 with room temperature antiferromagnetic order F. Damay et al. Phys. Rev. B 91, 214111 (2015)

LuFe2O4

hp-LuFe2O4