The low-temperature transition in magnetite

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

“…The symmetry changes from cubic to orthorhombic on cooling. 5 In certain crystallographic directions this transformation, we find, is accompanied by large effects in the moduli and internal friction. Stress-induced ordering is proposed as the explanation.…”

“…This was verified experimentally. 5,13 When the crystal becomes orthorhombic, the dimensions of the cubic lattice change, according to Bickford, 13 as follows: The c axis, direction of easy magnetization in the orthorhombic phase and normal to the plane of Fig. 6, shrinks 0.03 percent.…”

Instability of Crystal Lattices with Respect to Electron Density Redistributions

“…1). Below 119 "K, there is a distortion to orthorhombic synimetrp [12]. This deformation is very small but is accompanied by a large specific-heat anomaly [13].…”

Selected X-ray crystallographic data, molar volumes, and densities of minerals and related substances

“…Accordingly all ideal gases have the same molar volume at 25°0 (298.15°K) equal to :RT or 24465.0± 3.4 cm 3 mole-1 • For mineral equilibrium calculations at higher pressures, one needs to know the V dP term in the expression for the free energy. Accordingly, the molar volumes have been given in both the conventional units of cm 3 mole- 1 and also in terms of caJ.ories bar-1 to facilitate thermodynamic calculations.…”