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.