Effect of Heat Treatment on the Ultrasonic Attenuation in Mn-Ferrites
نویسندگان
چکیده
The acoustic losses in single crystals of manganese femtes 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.
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