Ultrasonic evidence for short-range charge-ordering state in the low-doping regime of La_1–xSr_xFeO₃ (1/3 ≤ x ≤ 0.45)

Abstract

The longitudinal ultrasonic velocity (V) and attenuation at a frequency of 10 MHz, as well as magnetization and resistivity, have been measured in the single-phase polycrystalline La_{1– x} Sr _x FeO₃ (x = 1/3, 0.4, 0.45). Upon cooling down from high temperature, a slight softening in V and dramatic stiffening are observed in all samples, and this stiffening is coincided with a big attenuation peak. The relative increase of V is proportional to the Sr concentration, which implies that this anomaly is strongly correlated with Fe⁴⁺. However, no obvious changes in magnetic and electric properties are found at this temperature range. The analysis suggests that this feature may be caused by the Jahn–Teller effect of Fe⁴⁺ and correspond to the formation of short-range charge-ordering state.

Keywords:

• charge ordering
• ultrasonic
• transition metal oxides
• Jahn–Teller effect
• electron–phonon interactions

Acknowledgments

This study was supported by the National Natural Science Foundation of China (No. 11004002).