Moduli and Internal Friction of Magnetite as Affected by the Low-Temperature Transformation

The low-temperature ordering transformation in magnetite is the source of large nonelastic effects. For example, Young's modulus for the $〈111〉$ direction at 108°K is 30 percent lower than the value one would estimate from higher-temperature measurements; an internal friction peak occurs near 95°K. We have attributed the nonelastic effects to stress-induced ordering of ${\mathrm{Fe}}^{++}$ and ${\mathrm{Fe}}^{+++}$ among the octahedral sites in the lattice.