A “checkerboard" orbital-stripe phase and charge ordering transitions in Pr(Sr$_{x}$Ca$_{2 - x}$)Mn$_{2}$O$_{7}$ (0 $\leqslant$ $x$ $\leqslant$ 0.45)

Z. A. Li; X. Li; Z. Wang; H. F. Tian; C. Ma; L. J. Zeng; H. X. Yang

doi:doi:10.1209/0295-5075/86/67010

EPL, 86 (2009) 67010
DOI: 10.1209/0295-5075/86/67010

A “checkerboard" orbital-stripe phase and charge ordering transitions in Pr(Sr_xCa_{2 - 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(Sr_xCa_2-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(Sr_xCa_2-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

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

A “checkerboard" orbital-stripe phase and charge ordering transitions in Pr(Sr_xCa_{2 - x})Mn₂O₇ (0 $\leqslant$ x $\leqslant$ 0.45)