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Magnetic field – temperature phase diagram
of multiferroic (NH4)2FeCl5∙H2O
A. J. Clune, K. D. Hughey, A. L. Blockmon, J. L. Musfeldt (UT); J. Nam, M. Lee, J. H. Lee (UNIST); W.
Tian, R. S. Fishman (ORNL); J. Fernandez-Baca (ORNL & UT); J. Singleton, M. Lee, V Zapf (LANL)
Objectives:
• explore molecule-based multiferroic (NH4)2FeCl5∙H2O in high magnetic fields
• reveal complex B-T phase diagram
• enable new types of property investigations
image of a single crystal
Multifunctional material vs. multiferroics?
Schmidt (1996); Spaldin + Fiebig, Science (2005)
E → P
σ → εH → M
Multifunctional: must combine >1 interesting functionalities
What are they?
ferroelectricity
ferromagnetism ferrotoroidicity
ferroelasticity
Extending this definition to include
non-primary order parameters…
ferrimagnetism antiferromagnetism
Appear in different forms…
single phase
composites
heterostructues
Cross-coupling gives rise to rich phase diagrams!
nanoparticles
Multiferroics: must have >1 primary ferroic order parameter
why molecule-based multiferroics?• molecule-based multiferroics
• low energy scales• flexible architecture
• chemical substitution• experimentally accessible fields!
• field-induced transitions to fully-saturated state under-explored
• how to fix this? • develop phase diagrams!• reveal properties
A. Clune, et al., PRB (2017)A. Narayan, et al., Nat. Mater. (2019)
[(CH3)2NH2]Mn(HCOO)3
Erythrosiderite (NH4)2FeCl5∙H2O
• space group: Pnma
• Fe+3 = 5/2
• TO/D = 79 K
• TN = 7.25 K
• TFE = 6.9 K
• multiferroic!
• mechanism is curious
(a) (d)(b)
(c)
6.4 6.8 7.20.0
0.5
1.0
1.5
2.0
2.5
J3
J4
J2
J5
-J (
K)
Distance between FeFe (Å)
J1(H
2O)
image of a single crystal
oh, the places you will go!
exotic properties emerge when phases compete!
Erythrosiderite (NH4)2FeCl5∙H2O
Ackermann, et al, New Journal of Physics (2013)
but what about the high field behavior?
Competition between exchange pathways
J1 = -2.51 KJ2 = -1.55 K
J4 = -1.25 K J5 = -0.71 K
J3 = -0.27 K
(a) (d)(b)
(c)
6.4 6.8 7.20.0
0.5
1.0
1.5
2.0
2.5
J3
J4
J2
J5
-J (
K)
Distance between FeFe (Å)
J1(H
2O)
Frustration!
Hydro
gen
tate
d, B
|| c
0 10 20 300.0
0.5
1.0
BSat
= 30.3 T
M/M
Sat
Magnetic Field (T)
0.60 K(a)
15 20 25 30
(f)
M
/B
Magnetic Field (T)
0.60 K
1.59 K
2.16 K2.54 K
3.09 K
3.62 K4.12 K
1 2 3 4 5 6
(e)
M
/B
Magnetic Field (T)
0.60 K1.59 K3.09 K4.12 K5.50 K
6.75 K6.25 K
0 10 20 300.0
0.5
1.0 (d)
BSat
= 30.3 T
M/M
Sat
Magnetic Field (T)
0.62 K
0 10 20 300.0
0.5
1.0 (c)
M/M
Sat
Magnetic Field (T)
0.66 K
BSat
= 31.1 T
0 10 20 300.0
0.5
1.0 (b)
BSat
= 30.1 T
M/M
Sat
Magnetic Field (T)
0.62 K
3.0 4.5 6.0
M
/B
Magnetic Field (T)
3.5 4.0 4.5
M
/B
Magnetic Field (T)
3.0 4.5
M
/B
Magnetic Field (T)
3.5 4.0 4.5
M
/B
Magnetic Field (T)
Mag
net
ic f
ield
|| a
Hydrogentated Deuterated
Mag
net
ic f
ield
|| c
Driving to the fully saturated state
• two sets of transitions
• Blow field < 6 T
• BSat ≈ 30 T
• shape consistent with
3D materials
Derivatives to reveal magnetic transitions
Hydro
gen
tate
d, B
|| c
0 10 20 300.0
0.5
1.0
BSat
= 30.3 T
M/M
Sat
Magnetic Field (T)
0.60 K(a)
15 20 25 30
(f)
M
/B
Magnetic Field (T)
0.60 K
1.59 K
2.16 K2.54 K
3.09 K
3.62 K4.12 K
1 2 3 4 5 6
(e)
M
/B
Magnetic Field (T)
0.60 K1.59 K3.09 K4.12 K5.50 K
6.75 K6.25 K
0 10 20 300.0
0.5
1.0 (d)
BSat
= 30.3 T
M/M
Sat
Magnetic Field (T)
0.62 K
0 10 20 300.0
0.5
1.0 (c)
M/M
Sat
Magnetic Field (T)
0.66 K
BSat
= 31.1 T
0 10 20 300.0
0.5
1.0 (b)
BSat
= 30.1 T
M/M
Sat
Magnetic Field (T)
0.62 K
3.0 4.5 6.0
M
/B
Magnetic Field (T)
3.5 4.0 4.5
M
/B
Magnetic Field (T)
3.0 4.5
M
/B
Magnetic Field (T)
3.5 4.0 4.5
M
/B
Magnetic Field (T)
Mag
net
ic f
ield
|| a
Hydrogentated Deuterated
Mag
net
ic f
ield
|| c
(a) (d)(b)
(c)
6.4 6.8 7.20.0
0.5
1.0
1.5
2.0
2.5
J3
J4
J2
J5
-J (
K)
Distance between FeFe (Å)
J1(H
2O)
J1
J2J4
J5 J3
0 2 4 6 80
5
10
15
20
25
30
35
Mag
net
ic F
ield
(T
)
Temperature (K)0 2 4 6 8
0
5
10
15
20
25
30
35
Mag
net
ic F
ield
(T
)
Temperature (K)0 2 4 6 8
0
5
10
15
20
25
30
35
Mag
net
ic F
ield
(T
)
Temperature (K)A. Clune, et al., npj Quant. Mater. (2019); Ackermann, et al., New Journal of Physics (2013); W. Tian, et al., PRB (2018)
• previous studies only went to 15 T
• transition to fully polarized state at 30.3 T
• linked to J1
J1
J1
Developing the phase diagram (hydrogenated B ║ c)
(NH4)2FeCl5.H2O… the full view
A. Clune, et al., npj Quant. Mater. (2019); Ackermann, et al., New Journal of Physics (2013); W. Tian, et al., PRB (2018)
electric polarization across the magnetic quantum phase transition?
A
- +
- +
P
B
Pulsed fields = very low noise!
Pulse up to 65 T
electric polarization across the magnetic quantum phase transition
consequences of Type II multiferroic:
ferroelectricity derives from magnetic order
spin-lattice interactions in multiferroics
[(CH3)2NH2]Mn(HCOO)3 (NH4)2FeCl5∙H2O
U
tJ AFM
2
~
K. D. Hughey, PRB 96, 180305 (2017).
phonon mode links
ferroicities!
?
Spin-phonon coupling in Ruby?
NH4 and H2O
librations
evaluate coupling constants?
What we learned…• able to drive molecular multiferroics into the
fully saturated state at realizable fields
• generated a rich + complex B-T phase diagram
• opens door to exploring high field properties
A. Clune, et. al, npj Quant. Mater. (2019)
We thank
NSF and NHMFL for
support of this work!
(a) (d)(b)
(c)
6.4 6.8 7.20.0
0.5
1.0
1.5
2.0
2.5
J3
J4
J2
J5
-J (
K)
Distance between FeFe (Å)
J1(H
2O)