Acoustic Relaxations in Ferrite Single Crystals

Acoustical wave attenuation measurements have shown the existence of two types of stress-induced relaxations and a transformation in the ferrites examined. A loss mechanism due to stress-induced electron migration of the type Fe++++e⇄Fe++, with an activation energy of 0.03±0.004 ev per electron jump, appears to be common to all ferrites containing di- and trivalent ferrous ions on the octahedral sites. A stress-induced relaxation has been demonstrated in manganese ferrite, with an activation energy of about 0.3 ev per unit process. This relaxation process is sensitive to composition and homogeneity. Finally, a transformation has been observed in manganese zinc ferrite near 10°K, the temperature depending upon composition. A similar transformation probably occurs in manganese ferrite below 1.25°K. Below the transition temperature the intensity of magnetization is found to decrease with decreasing temperature.