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Magnetite is a mineral and one of the main iron ores, with the chemical formula Fe 2+ Fe 3+ 2 O 4. ... The Curie temperature of magnetite is 580 °C (853 K; 1,076 °F).
Above the Curie temperature, the magnetic spins are randomly aligned in a paramagnet unless a magnetic field is applied. In physics and materials science, the Curie temperature (TC), or Curie point, is the temperature above which certain materials lose their permanent magnetic properties, which can (in most cases) be replaced by induced magnetism.
The Verwey transition is a low-temperature phase transition in the mineral magnetite associated with changes in its magnetic, electrical, and thermal properties. [1] It typically occurs near a temperature of 120 K but is observed at a range of temperatures between 80 and 125 K, although the spread is generally tight around 118-120 K in natural magnetites.
The Curie temperature of magnetite, a spinel-group iron oxide, is about 580 °C (1,076 °F), whereas most basalt and gabbro are completely crystallized at temperatures below 900 °C (1,650 °F). Hence, the mineral grains are not rotated physically to align with Earth's magnetic field, but rather they may record the orientation of that field.
Tammann temperature was pioneered by German astronomer, solid-state chemistry, and physics professor Gustav Tammann in the first half of the 20th century. [1]: 152 He had considered a lattice motion very important for the reactivity of matter and quantified his theory by calculating a ratio of the given material temperatures at solid-liquid phases at absolute temperatures.
H {\displaystyle H} is the magnitude of the applied magnetic field (A/m), T {\displaystyle T} is absolute temperature (K), C {\displaystyle C} is a material-specific Curie constant (K). Pierre Curie discovered this relation, now known as Curie's law, by fitting data from experiment. It only holds for high temperatures and weak magnetic fields.
These temperature dependencies have also been experimentally observed in NiFe 2/5 Cr 8/5 O 4 [8] and Li 1/2 Fe 5/4 Ce 5/4 O 4. [9] A temperature lower than the Curie temperature, but at which the opposing magnetic moments are equal (resulting in a net magnetic moment of zero) is called a magnetization compensation point. This compensation point ...
The involved processes are complex and depend on the reduction temperature: At lower temperatures, wüstite disproportionates into an iron phase and a magnetite phase; at higher temperatures, the reduction of the wüstite and magnetite to iron dominates. [43] The α-iron forms primary crystallites with a diameter of about 30 nanometers.