Low-Temperature Acoustic Relaxation in Ni—Fe Ferrites

Abstract

An acoustic relaxation effect occurs near 40°K in ${\mathrm{Ni}}_{0.75}$ ${\mathrm{Fe}}_{2.25}$ ${\mathrm{O}}_4$ and is attributed to a stress-induced change in distribution of ${\mathrm{Fe}}^{++}$ and ${\mathrm{Fe}}^{+++}$ similar to that occurring in magnetite. The process involves electron diffusion. The activation energy is between 0.026 and 0.055 ev per electron jump.