Hematite: intrinsic and defect ferromagnetism.
Both intrinsic (spin-canted) ferromagnetism and defect ferromagnetism occur in hematite. Because defect ferromagnetism is sensitive to structure, it is altered by stress or heating and could give spurious paleomagnetic information. Annealing experiments now suggest that the defect remanence of fine-grain hematites and red sediments, unlike that of single crystals, is magnetically softer than the spin-canted remanence and can be erased by partial demagnetization.
Dunlop
D J
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