Acoustic properties of multiferroics PbFe<inf>1/2</inf>Ta<inf>1/2</inf>O<inf>3</inf> and BiFeO<inf>3</inf> at Néel temperature

Abstract

The longitudinal acoustic wave velocity and attenuation in PbFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sub> Ta <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> and BiFeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ceramics have been measured by ultrasonic pulse-echo technique in the temperature range from 50 K to 530 K and from 250 K to 830K, respectively. The anomalies observed in the sound velocity behavior versus temperature in the case of PbFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sub> Ta <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> were correlated with Burns temperature and temperature range of relaxor ferroelectric and antiferromagnetic states coexistence. BiFeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> demonstrates wide minimum of acoustic wave velocity at Neél temperature. Magnetostriction along with order parameter fluctuations are discussed as the factors determining the acoustic wave velocity anomaly in the vicinity of the antiferromagnetic phase transition point.