Dynamic Jahn–Teller distortion and oxygen vacancies in (La1−xPrx)1/3Sr2/3FeO3−δ investigated by mechanical spectroscopy

•The dynamic Jahn–Teller distortion changes with Pr substitution in LSFO.•The magnetic properties were affected by the oxygen vacancy.•The abruptness of the CO transition was reduced by the oxygen vacancy.

We present the results of the low temperature kilohertz mechanical spectrum of air sintered (La1−xPrx)1/3Sr2/3FeO3−δ (x=0, 0.1, 0.3, 0.5, 0.7, 0.9, and 1.0) samples. A step-like change of mechanical spectrum was observed around the charge ordering (CO) transition temperature TCO in La1/3Sr2/3FeO3−δ. By substitution of smaller-size Pr ion for La ion, TCO shifts towards lower temperature with the increase of Pr doping. The CO transition was suppressed in (La1−xPrx)1/3Sr2/3FeO3−δ with x=0.9 and 1.0 as indicated by the resistivity. However, the phase transition was observed in x=0.9 sample by specific heat, magnetic measurement and mechanical spectrum. The imprint of the phase transition was found in x=1.0 sample from the modulus softening in the mechanical spectrum. These diverse behaviors show the evolution of the dynamic Jahn–Teller distortion and oxygen vacancies in Pr substituted (La1−xPrx)1/3Sr2/3FeO3−δ.