Issue
EPL
Volume 86, Number 5, June 2009
Article Number 54001
Number of page(s) 5
Section Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics
DOI http://dx.doi.org/10.1209/0295-5075/86/54001
Published online 09 June 2009
EPL, 86 (2009) 54001
DOI: 10.1209/0295-5075/86/54001

Variation of ultrasonic behaviors in R1/3Sr2/3FeO3 (R = La, Pr, Gd)

Hui Kong1, 2 and Changfei Zhu1

1   Laboratory of Advanced Functional Materials and Devices, Department of Materials Science and Engineering, University of Science and Technology of China - Hefei, Anhui, 230026, PRC
2   School of Metallurgy and Resources, Anhui University of Technology - Maanshan, Anhui, 243002, PRC

cfzhu@ustc.edu.cn

received 10 December 2008; accepted in final form 7 May 2009; published June 2009
published online 9 June 2009

Abstract
The longitudinal ultrasonic velocity (V), as well as resistivity and magnetization has been measured in polycrystalline R1/3Sr2/3FeO3 (R = La, Pr, Gd). When the R-site ion is changed from La to smaller-size R ion, the charge ordering (CO) transition shifts to lower temperature and finally disappears for R = Gd. Dramatic anomalies in V for the R = La, Pr compounds are observed near the CO transition temperature, which implies the electron-phonon coupling arising from the Jahn-Teller effect of Fe4+. And the theory calculation result shows that this coupling is weakened for Pr, which may lead to the shift of $T_{{\rm CO}}$. In the case of Gd1/3Sr2/3FeO3 with no CO transition, the anomaly in V is small, and may be attributed to the antiferromagnetic spin fluctuations. Below $T_{{\rm CO}}$, another unexpected softening in V is discerned in La1/3Sr2/3FeO3, while only a slope change is observed in Pr1/3Sr2/3FeO3. This feature is attributed to the breathing-type distortion of Fe-O octahedron via the charge disproportionation, which is weakened in Pr1/3Sr2/3FeO3.

PACS
43.35.+d - Ultrasonics, quantum acoustics, and physical effects of sound.
64.70.K- - Solid-solid transitions.
71.38.-k - Polarons and electron-phonon interactions.

© EPLA 2009