Download Podlesnyak, Andrey: Spin crossover phenomena in transition metal

Spin crossover phenomena
in transition metal oxides
under high magnetic field
Andrey Podlesnyak
Quantum Condensed Matter Division,
Neutron Sciences Directorate,
Oak Ridge National Laboratory
[email protected]
ORNL is managed by UT-Battelle
for the US Department of Energy
OUTLINE
1. Spin crossover - fascinating
electronic structure phenomena
2. The origin of spin crossover
3. Magnetic field as a tool to analyze
spin-state transitions
4. Magnetic field as a tool to
manipulate with electronic states
5. Conclusions
2 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30
OUTLINE
1. Spin crossover - fascinating
electronic structure phenomena
2. The origin of spin crossover
3. Magnetic field as a tool to analyze
spin-state transitions
4. Magnetic field as a tool to
manipulate with electronic states
5. Conclusions
3 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30
OUTLINE
1. Spin crossover - fascinating
electronic structure phenomena
2. The origin of spin crossover
3. Magnetic field as a tool to analyze
spin-state transitions
4. Magnetic field as a tool to
manipulate with electronic states
5. Conclusions
4 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30
OUTLINE
1. Spin crossover - fascinating
electronic structure phenomena
2. The origin of spin crossover
3. Magnetic field as a tool to analyze
spin-state transitions
4. Magnetic field as a tool to
manipulate with electronic states
5. Conclusions
5 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30
Prussian blue was synthesized for the first time
in Berlin in 1703. Its intense color arises
from a charge transfer transition between
the FeII HS and FeIII LS ion, which occurs
when light in the red region of the visible
spectrum is absorbed.
KFeIII[FeII(CN)6]·xH2O
Pablo Picasso, The Old Guitarist (1903),
Art Institute of Chicago. The Blue Period
6 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30
Prussian blue was synthesized for the first time
in Berlin in 1703. Its intense color arises
from a charge transfer transition between
the FeII HS and FeIII LS ion, which occurs
when light in the red region of the visible
spectrum is absorbed.
KFeIII[FeII(CN)6]·xH2O
Pablo Picasso, The Old Guitarist (1903),
Art Institute of Chicago. The Blue Period
7 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30
Thermal, pressure-induced and magnetic-field spin crossovers
A mononuclear ferric complex
[Fe(H-5-Br-thsa)(5-Br-thsa)]⋅H2O
shows unprecedented reversible
six-step spin-crossover behavior.
Zhao-Yang Li, et al., Chemistry - A
European Journal 19, 12948 (2013)
Pressure-Induced Cooperative Spin
Transition in Iron(II) 2D Coordination Polymers [Fe(3-Fpy)2MII(CN)4],
(MII = Ni, Pd, Pt)
G. Levchenko, et al., J. Phys. Chem. B
115, 8176 (2011)
Set of isotherms showing the
triggering effect on the HS
fraction in Co(H2(fsa)2en)(py)2.
Bousseksou A., et al., Phys. Rev B 65,
172412 (2002)
8 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30
Electric and photo-induced spin crossover
9 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30
The origin of spin crossover
orbitals forming eg set
orbitals forming t2g set
The difference in energy between the eg and the t2g energy levels is the crystal field splitting parameter, Do.
The Pairing Energy P is the energy required to pair two electrons
10 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30
The origin of spin crossover
Intermediate
spin state
High spin state
eg
Low spin state
eg
eg
∆ο
∆o
t2g
t2g
t2g
∆ is small
∆ is large
∆o < P
∆o > P
electrons occupy eg and t2g orbitals
singly before pairing
11 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30
electrons pair in t2g oribtals before
occupying eg orbitals
Spin-state puzzle in the cobaltites
Ground state electron configuration: [Ar].3d7.4s2
Low spin state
Intermediate
spin state
High spin state
Co2+ (3d7)
S=1/2
Co3+ (3d6)
S=0
S=1
S=2
Co4+ (3d5)
S=1/2
S=3/2
S=5/2
12 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30
S=3/2
OUTLINE
1. Spin crossover - fascinating electronic structure phenomena
2. The origin of spin crossover
3. Magnetic field as a tool to analyze spin-state transitions
4. Magnetic field as a tool to manipulate with electronic states
5. Conclusions
13 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30
Intermediate vs high spin state
[Ar].3d7.4s2
z
Co
xy
La
O
Rhombohedral unit cell of LaCoO3
Possible electronic configurations
of Co3+ ions
14 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30
K. Azai, et al., J.Phys.Soc.Jpn. 67 (1998) 290.
Intermediate vs high spin state
Intermediate spin state!
High-Field Magnetostriction, K. Sato, et al., J.Phys.Soc.Jpn. 77 (2008) 024601
Photoemission spectroscopy, K. Azai, et al., J.Phys.Soc.Jpn. 67 (1998) 290
Magnetic susceptibility, C. Zobel, et al., Phys. Rev. B 66 (2002) R020402
Infrared spectroscopy, S. Yamaguchi, et al., Phys. Rev. B 55 (1998) R8666
Raman spectroscopy, A. Ishikawa, et al., Phys. Rev. Lett. 93 (2004) 136401
LDA+U calculations, M. Korotin, et al., Phys. Rev. B 54 (1996) 5309
High spin state!
Electron spin resonance, S. Noguchi, et al., Phys. Rev. B 66 (2002) 094404
Magnetic susceptibility, T. Kyomen, et al., Phys. Rev. B 67 (2003) 144424
Heat capacity, T. Kyomen, et al., Phys. Rev. B 71 (2005) 024418
Hartree-Fock calculations, M. Zhuang, et al., Phys. Rev. B 57 (1998) 10705
CoO6 claster calculations, M. Haverkort, et al., Phys. Rev. Lett. 97 (2006) 176405
...
15 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30
Intermediate vs high spin state
Temperature evolution of the INS profiles measured
in LaCoO3. The filled circles correspond to the LaAlO3
nonmagnetic reference compound at T = 50 K.
Observed and fitted temperature dependence of the
integral intensity of the INS peak at 0.6 meV.
A. Podlesnyak, et al., PRL 101 (2008) 247603.
IS: S=1, L=1, J=2
e1g
S=1
HS: S=2, L=1, J=1
eg2
4
t2g
5
t2g
M. Haverkort, PhD thesis, cond-mat/0505214 (2005)
16 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30
J=1
Intermediate vs high spin state
HS |+1>
14
One striking difference between these
scenarios: this is the predicted g-factor.
IS |0> -> |+1>
dE (meV)
10
The HS state is a triplet with a g-factor of
about 3.5,
whereas the IS has g-factor of about 2.0.
IS |+1>
HS |0> -> |+1>
12
|0>
8
IS | -1>
6
HS |-1>
ΔE = µB g S B0
4
2
LS
0
0
2
4
6
8
10
12
14
B0 (T)
IS: S=1, L=1, J=2
e1g
S=1
HS: S=2, L=1, J=1
eg2
4
t2g
5
t2g
M. Haverkort, PhD thesis, cond-mat/0505214 (2005)
17 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30
J=1
16
18
20
Intermediate vs high spin state
HS!
HS |+1>
14
IS |0> -> |+1>
10
dE (meV)
IS |+1>
HS |0> -> |+1>
12
|0>
8
IS | -1>
6
HS |-1>
ΔE = µB g S B0
4
2
The magnetic inelastic scattering at T = 50K
in 0T (circles) and 6T (boxes) applied field.
LS
0
0
2
4
6
8
10
12
14
B0 (T)
IS: S=1, L=1, J=2
e1g
S=1
HS: S=2, L=1, J=1
eg2
4
t2g
5
t2g
M. Haverkort, PhD thesis, cond-mat/0505214 (2005)
18 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30
J=1
16
18
20
Evolution of the INS in the magnetic field
La0.998Sr0.002CoO3
Temperature dependence of the magnetic susceptibility
for lightly doped crystals of La1-xSrxCoO3
A. Podlesnyak, et al., PRL 101 (2008) 247603.
S. Yamaguchi, et al., Phys. Rev. B 53 (1996) R2926
19 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30
Evolution of the INS in the magnetic field
La0.998Sr0.002CoO3, T=2K
1.2
400
H=0.4T
?!, M=15µB
1.0
300
Co4+ HS
H=0.3T
∆E, meV
Neutron counts
0.8
200
H=0.2T
Co4+IS
0.6
0.4
100
H=0T
0.2
0
0.0
-1.5
-1.0
-0.5
Energy transfer, meV
0.0
0.0
0.1
0.2
0.3
H, T
0.4
0.5
0.6
Spin-state polaron in La1-xSrxCoO3
A. Podlesnyak, et al., PRB 83 (2011) 134430.
A. Podlesnyak, et al., PRL 101 (2008) 247603.
Spin-state polaron in La1-xSrxCoO3
Co3+, IS
Co4+, LS
eg
t2g
Co4+, LS
Co3+, IS
eg
t2g
A. Podlesnyak, et al., PRB 83 (2011) 134430.
23 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30
OUTLINE
1. Spin crossover - fascinating electronic structure phenomena
2. The origin of spin crossover
3. Magnetic field as a tool to analyze spin-state transitions
4. Magnetic field as a tool to manipulate with
electronic states
5. Conclusions
24 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30
HS |+1>
14
IS |0> -> |+1>
10
dE (meV)
IS |+1>
HS |0> -> |+1>
12
|0>
8
IS | -1>
6
HS |-1>
4
2
LS
0
0
2
4
6
8
10
B0 (T)
25 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30
12
14
16
18
20
14
12
10
dE (meV)
8
6
4
2
IS |-1>
0
0
-2
10
20
30
40
50
60
70
80
90
100
B0 (T)
-4
HS |-1>
26 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30
14
12
10
dE (meV)
8
6
4
2
IS |-1>
0
0
-2
10
20
30
40
50
60
70
80
90
100
B0 (T)
-4
HS |-1>
27 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30
28 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30
SUMMARY
 Spin crossover - fascinating electronic structure phenomena.
 We are waiting for strong magnetic fields to become available to INS:
 a “must” tool to analyze spin-state transitions;
 to manipulate with electronic states.
29 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30
Georg Ehlers,
Quantum Condensed Matter Division,
ORNL, Oak Ridge TN, USA
Margarita Russina,
The Helmholtz Centre Berlin
for Materials and Energy, Germany
Albert Furrer,
Thierry Strässle,
Laboratory for Neutron Scattering,
Paul Scherrer Institute, Switzerland.
Kazimierz Conder,
Ekaterina Pomjakushina,
Peter Allenspach,
Laboratory for Developments and Methods,
Paul Scherrer Institute, Switzerland.
Maurits Haverkort,
Daniel Khomskii,
II Physikalisches Institut,
Universität zu Köln, Köln, Germany.
30 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30
Vincent van Gogh's Starry Night uses
Prussian blue pigments.
31 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30
32 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30
33 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30
Intermediate spin state
e1g
S=1
5
t2g
(x2-y2)1(xy)1
(z2)1(xy)1
Georg Ehlers,
Quantum Condensed Matter Division,
ORNL, Oak Ridge TN, USA
Margarita Russina,
The Helmholtz Centre Berlin
for Materials and Energy, Germany
Albert Furrer,
Thierry Strässle,
Laboratory for Neutron Scattering,
Paul Scherrer Institute, Switzerland.
Kazimierz Conder,
Ekaterina Pomjakushina,
Peter Allenspach,
Laboratory for Developments and Methods,
Paul Scherrer Institute, Switzerland.
Maurits Haverkort,
Daniel Khomskii,
II Physikalisches Institut,
Universität zu Köln, Köln, Germany.
35 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30
Vincent van Gogh's Starry Night uses
Prussian blue pigments.
Intermediate spin state
=
S 1=
L 1=
J 0,1,2
(x2-y2)1(xy)1
M. Haverkort, PhD thesis, cond-mat/0505214 (2005)
High spin state
S=1
=
S 2=
L 1=
J 1,2,3
e g2
4
t2g
M. Haverkort, PhD thesis, cond-mat/0505214 (2005)
38 Andrey Podlesnyak, Neutron Scattering in Magnetic Fields Above 15 Tesla, October 29-30