Abstract
Chromium (II) fluoroperovskites
A
CrF
3
(
A
=
Na
+
,
K
+
)
are strongly correlated Jahn-Teller active materials at low temperatures. In this paper, we examine the role that the
A
-site ion plays in this family of fluoroperovskites using both experimental methods (x-ray diffraction, optical absorption spectroscopy, and magnetic fields) and density functional theory simulations. Temperature-dependent optical absorption experiments show that the spin-allowed transitions
E
2
and
E
3
only merge completely for
A
=
Na
at 2 K. Field-dependent optical absorption measurements at 2 K show that the oscillating strength of the spin-allowed transitions in
NaCrF
3
increases with increasing applied field. Direct magneto-optical correlations suppress the spin-flip transitions for
KCrF
3
below its Néel temperature. In
NaCrF
3
the spin-flip transitions vanish abruptly below 9 K revealing magneto-optical correlations possibly linked to crystal structure changes. This suggests that as the long range ordering is reduced, local Jahn-Teller effects in the individual
CrF
4
−
6
octahedra take control of the observed behavior. Our results show clear deviation from the pattern found for the isoelectronic
A
x
MnF
3
+
x
system. The size of the
A
-site cation is shown to be central in dictating the physical properties and phase transitions in
A
CrF
3
, opening up the possibility of varying the composition to create novel states of matter with tunable properties.
A
CrF
3
(
A
=
Na
+
,
K
+
)
are strongly correlated Jahn-Teller active materials at low temperatures. In this paper, we examine the role that the
A
-site ion plays in this family of fluoroperovskites using both experimental methods (x-ray diffraction, optical absorption spectroscopy, and magnetic fields) and density functional theory simulations. Temperature-dependent optical absorption experiments show that the spin-allowed transitions
E
2
and
E
3
only merge completely for
A
=
Na
at 2 K. Field-dependent optical absorption measurements at 2 K show that the oscillating strength of the spin-allowed transitions in
NaCrF
3
increases with increasing applied field. Direct magneto-optical correlations suppress the spin-flip transitions for
KCrF
3
below its Néel temperature. In
NaCrF
3
the spin-flip transitions vanish abruptly below 9 K revealing magneto-optical correlations possibly linked to crystal structure changes. This suggests that as the long range ordering is reduced, local Jahn-Teller effects in the individual
CrF
4
−
6
octahedra take control of the observed behavior. Our results show clear deviation from the pattern found for the isoelectronic
A
x
MnF
3
+
x
system. The size of the
A
-site cation is shown to be central in dictating the physical properties and phase transitions in
A
CrF
3
, opening up the possibility of varying the composition to create novel states of matter with tunable properties.