Issue
EPL
Volume 86, Number 6, June 2009
Article Number 67010
Number of page(s) 5
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
DOI http://dx.doi.org/10.1209/0295-5075/86/67010
Published online 13 July 2009
EPL, 86 (2009) 67010
DOI: 10.1209/0295-5075/86/67010

A “checkerboard" orbital-stripe phase and charge ordering transitions in Pr(SrxCa2 - x)Mn2O7 (0 $\leqslant$ x $\leqslant$ 0.45)

Z. A. Li1, X. Li2, Z. Wang1, H. F. Tian1, C. Ma1, L. J. Zeng1 and H. X. Yang1

1   Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences Beijing 100080, China
2   Department of Communication Engineering, School of Information Engineering, University of Science and Technology Beijing 100083, China

hxyang@aphy.iphy.ac.cn

received 5 May 2009; accepted in final form 2 June 2009; published June 2009
published online 13 July 2009

Abstract
The charge/orbital ordering (COO) behaviors in the double-layered Pr(SrxCa2-x)Mn2O7 have been investigated by in situ transmission electron microscopy (TEM) observations. The experimental results reveal that two charge ordering (CO) phase transitions, so-called $T_{{\rm co}1}$ and $T_{{\rm co}2}$, commonly exist in the orthorhombic Pr(SrxCa2-x)Mn2O7 (0 $\leqslant$ x $\leqslant$ 0.45) samples. Moreover, a “checkerboard" orbital-stripe phase characterized by two orthogonal COO modulations, $\vect{ q}_{a}$ and $\vect{ q}_{b}$, is observed between $T_{{\rm co}1}$ and $T_{{\rm co}2}$ in all samples. Detailed TEM investigations on the x=0.2 sample, in which a visible electric polarization was found (TOKUNAGA Y. et al., Nat. Mater.5 (2006) 937) demonstrate that the $\vect{ q}_{b}$ modulation only survives between $T_{{\rm co}1}$ and $T_{{\rm co}2}$, and the “checkerboard” phase transforms into the conventional one-dimensional COO stripe phase below $T_{{\rm co}2}$. The reversal of in-plane optical anisotropy across the $T_{{\rm co}2}$ transition (TOKUNAGA Y. et al., Nat. Mater.5 (2006) 937) is also explained based on TEM result.

PACS
71.27.+a - Strongly correlated electron systems; heavy fermions.
71.30.+h - Metal-insulator transitions and other electronic transitions.
61.05.J- - Electron diffraction and scattering.

© EPLA 2009