Undirectional Diagonal Order and Three-Dimensional Stacking of Charge Stripes in Orthorhombic Pr1.67Sr0.33NiO4 and Nd1.67Sr0.33NiO4

The interplay between crystal symmetry and charge stripe order in Pr{sub 1.67}Sr{sub 0.33}NiO{sub 4} and Nd{sub 1.67}Sr{sub 0.33}NiO{sub 4} has been studied by means of single crystal x-ray diffraction. In contrast to tetragonal La{sub 1.67}Sr{sub 0.33}NiO{sub 4}, these crystals are orthorhombic. Th...

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Bibliographic Details
Published in:Physical review letters 2006-01, Vol.74
Main Authors: Hucker,M., Zimmermann, M., Klingelar, R., Kiele, S., Geck, J., Bakehe, S., Zhang, J., Hill, J., Revcolevschi, A., et al
Format: Article
Language:English
Subjects:
CRYSTAL STRUCTURE
DEGREES OF FREEDOM
DIMENSIONS
ELECTRON MICROSCOPY
GROUND STATES
MATERIALS SCIENCE
MELTING
MONOCRYSTALS
national synchrotron light source
OXYGEN
SPIN
SYMMETRY
X-RAY DIFFRACTION
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Summary:The interplay between crystal symmetry and charge stripe order in Pr{sub 1.67}Sr{sub 0.33}NiO{sub 4} and Nd{sub 1.67}Sr{sub 0.33}NiO{sub 4} has been studied by means of single crystal x-ray diffraction. In contrast to tetragonal La{sub 1.67}Sr{sub 0.33}NiO{sub 4}, these crystals are orthorhombic. The corresponding distortion of the NiO{sub 2} planes is found to dictate the direction of the charge stripes, similar to the case of diagonal spin stripes in the insulating phase of La{sub 2-x}Sr{sub x}CuO{sub 4}. In particular, diagonal stripes seem to always run along the short a axis, which is the direction of the octahedral tilt axis. In contrast, no influence of the crystal symmetry on the charge stripe ordering temperature itself was observed, with T{sub CO}{approx}240 K for La, Pr, and Nd. The coupling between lattice and stripe degrees of freedom allows one to produce macroscopic samples with unidirectional stripe order. In samples with stoichiometric oxygen content and a hole concentration of exactly 1/3, charge stripes exhibit a staggered stacking order with a period of three NiO{sub 2} layers, previously only observed with electron microscopy in domains of mesoscopic dimensions. Remarkably, this stacking order starts to melt about 40 K below T{sub CO}. The melting process can be described by mixing the ground state, which has a three-layer stacking period, with an increasing volume fraction with a two-layer stacking period.
ISSN:0031-9007
1079-7114