A transmission electron microscopy study on the real structure of synthetic hematite
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The magnetic properties of hematite (α-Fe2O3), the most important iron ore, have been extensively studied. It shows a Morin transition—a magnetic phase transition from an antiferromagnetic state to a weakly ferromagnetic one. The spins of the low-temperature phase order antiferromagnetically along the rhombohedral  direction. Those of the high-temperature phase order antiferromagnetically in the (111) plane, with a slight tilt out of plane, which leads to the ferromagnetic component. The Morin transition in pure hematite is known to be strongly dependent on the real structure of the investigated sample: Grain size, substitution for Fe by other metals, incorporation of water or OH− groups due to various synthesis routes influence the spin ordering of the hematite. Dang et al.  reviewed published work and successfully established a correlation between the lattice parameters and the Morin transition. They correlated the varying lattice parameters to different defect structures,...
KeywordsHematite Hematite Particle Morin Transition Threefold Symmetry Hematite Sample
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