Structural Aspects of Charge Disproportionation Transition in La$_{x}$Sr$_{1-x}$FeO$_{3-y}$ ($x$=1/10, 1/3, and 1/2)

다국어 초록 (Multilingual Abstract)

The aspects of the charge disproportionation transition for polycrystalline LaxSr1ကxFeO3ကy(x =
1/2, 1/3, and 1/10) near the transition temperature are investigated using Mossbauerspectroscopy
in relevance with their chemical and crystallographic data.
As the lanthanum content x is increased, both the rhombohrdral lattice constant aR and the
edge angle R increase, resulting in a slight increase in the tolerance factor t. For x = 1/3, a
rst-order-like transition between the low-temperature antiferromagnetic mixed-valence state and
the high-temperature paramagnetic average-valence state takes place in the temperature range
between 175 K and 200 K. With an increase in x from 1/3 to 1/2, this transition becomes blurred
by the weakened p-d hybridization due to the slight decrease in the bond angle (\Fe-O-Fe) from
180 with its transition temperature eectively unchanged. For the case of x = 1/10, the electron
delocalization takes place at considerably low temperature, and LaxSr1ကxFeO3ကyis paramagnetic
in the temperature region examined. This comes from a reduction of electron transfer energy due
to contractions in the bond lengths.

참고문헌 (Reference)

1 "General StructureAnalysys System" (Los AlamosNational Laboratory, Los Alamos 1990

2 "Elements of X-Ray Di raction, 2nd ed." Addison Wesley, Massachusetts 1978