J. Phys. IV France 07 (1997) C1-223-C1-224
Effect of Heat Treatment on the Ultrasonic Attenuation in Mn-FerritesY. Kawai1, V.A.M. Brabers2 and Z. Simsa3
1 Gakushuin University, 1-5-1 Meijiro, Tokyo 171, Japan
2 University of Technology, 5600 Eindhoven, The Netherlands
3 Institute of Physics ASCR, Cukrovarnická 10 , 162 00 Praha 6, Czech Republic
The acoustic losses in single crystals of manganese ferrites were studied in the temperature range from 180 to 650 K by applying longitudinal vibrations of 150 kHz. Loss peaks were observed at 232 and 537 K with activation energies of 0.3 and 0.8 eV, respectively. The first loss peak at 232 K is regarded as a stress-induced relaxation of electrons between two and three-valent ions. The second peak at 537 K is ascribed to the exchange motion of iron cations and their vacancies on octahedral sites. Heat treatments at 300 and 600°C affect the oxygen stoichiometry and distribution of cations between octahedral and tetrahedral sites which results in the changes of the loss peaks magnitudes.
© EDP Sciences 1997