Cation composition dependence of superlattice reflections in (Sr/Ca/La)14Cu24O41 (CROSBI ID 575954)
Prilog sa skupa u zborniku | sažetak izlaganja sa skupa | međunarodna recenzija
Podaci o odgovornosti
Milat, Ognjen
engleski
Cation composition dependence of superlattice reflections in (Sr/Ca/La)14Cu24O41
Crystallographic structure of the (Sr/La/Ca)14Cu24O41 “chainladder” compounds is complex [1] due to being composed of two interpenetrated subsystems with lattice parameters mutually incommensurate along one direction. “Ladder”-subsystem is formed by the (Sr/La/Ca)2Cu2O3 layers on an orthorhombic (Fmmm) lattice, and “chain”-subsystem consists of the CuO2 interleaved layers on an (Amma) lattice [2]. While cell parameters a (≈1.14nm) and b (≈1.34nm) are common for both lattices regardless of the cation composition, the misfit between the c-parameters is found to depend on substitution and doping. The cLd/cCh ratio is always close to √2, but varies from 1.45 to 1.41 [3] for pure Sr14Cu24O41, to Sr2Ca12Cu24O41, respectively, being roughly 1.43 in La/Ca for Sr substituted La6Ca8Cu24O41. In addition, partial substitution of La for Sr affects electronic structure by reducing hole-doping on Cu2+δ. A lot of doubt has recently emerged about doped hole ordering into Wigner crystal (WC) on the 5cLd or 3cLd superlattice cells, as found by RXS [4]. This ordering is allocated onto “ladder” subsystem due to observation of weak RXS spots at reciprocal positions commensurate with “ladder”, but not with “chain” basic spots. Here, we present detailed electron diffraction study of the corresponding 4-dim reciprocal lattice, and prove that all spots can be indexed: H = ha* + kb* + lcLd* + mcCh*. Spot`s intensity depends more on local imaging conditions and degree of order, then on nominal composition. By varying the Sr/La/Ca composition and the corresponding cLd/cCh ratio, all reciprocal lattice points shift in positions along c* ; the range (1/5cLd*- 1/3cLd*), coinciding to (1/7.1cCh*- 1/4.3cCh*), is swept by the weak spot 0046. Therefore, the peaks observed in that range should be assigned as 0046 reflection, and could not be exclusively related to “hole" superlattice formation in “ladder” subsystem only, as claimed for 5cLd WC in Sr14Cu24O41 [4]
composite crystal; electron diffraction; charge ordering
nije evidentirano
nije evidentirano
nije evidentirano
nije evidentirano
nije evidentirano
nije evidentirano
Podaci o prilogu
s63-s63.
2010.
objavljeno
Podaci o matičnoj publikaciji
Acta Crystallographica A66 (Supplement) ; Abstracts 26th European Crystallographic Meeting
Fuess Hartmut
Darmstadt: International Union of Crystallography
Podaci o skupu
26th European Crystallographic Meeting, ECM 26, Darmstadt, 2010
predavanje
29.08.2010-02.09.2010
Darmstadt, Njemačka