Resonant x-ray scattering in La1-xSr1+xMn04 (x≥0.5): Incommensurate-lattice modulation vs. Charge-stripe models

Workshop on Resonant Elastic X-ray Scattering in Condensed Matter 2013

Subías, G.^1 ; García, J.^1 ; Herrero-Martín, J.^2 ; Blasco, J.^1 ; Sánchez, M.C.^1

Instituto de Ciencia de Materiales de Aragón, Departamento de Fisica de la Materia Condensada, CSIC-Universidad de Zaragoza, Pedro Cerbuna 12, 50009-Zaragoza, Spain^1

ALBA Synchrotron Radiation Facility, Crta. BP 1413 Km 3.3, Cerdanyola del Vallès, 08290, Barcelona, Spain^2

关键词: Charge disproportionation;    Incommensurate lattice;    Incommensurate phase;    Lattice modulations;    Modulation vectors;    Resonant reflection;    Resonant X-ray scattering;    Sinusoidal modulation;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/519/1/012008/pdf
DOI  :  10.1088/1742-6596/519/1/012008

来源: IOP

【 摘 要 】

Using resonant x-ray scattering at the Mn K-edge, we have investigated the nature of the charge and lattice modulation in the La1-xSr1+xMnO4 (x=0.5 and 0.6) manganites. Resonant reflections (h±epsi;, h±Ε, 0) and (h±2Ε, h±2Ε, 0) of the tetragonal I4/mmm structure with a modulation vector of 2e=l-x were found in the insulating phases of both manganites but the intensity of these reflections is much weaker for La0.4Sr1.6MnO4. Resonant x-ray scattering data for the two samples are well explained by the presence of two types of sinusoidal modulations of the oxygen displacements, transverse and longitudinal to the tetragonal [110] direction. The amplitude of the oxygen displacements for any of the modulations decreases with the hole doping, in agreement with the change from a commensurate (x=0.5) to an incommensurate (x=0.6) ordered phase. The different polarization and azimuthal behaviour of the two sets of resonant reflections rule out any kind of stripe model composed by Mn3+-like and Mn4+-like charge-ordering. The maximum charge disproportionation among the different Mn atoms in the unit cell is about 0.15 e-and 0.04 e-for the x=0.5 and x=0.6 samples, respectively. These results thus confirm the existence of a charge-density-wave ordering in both the commensurate-phase of the half-doped La0.5Sr1.5MnO4 and the incommensurate-phase of the over-doped La0.4Sr1.6MnO4 manganites.