Morin transition

{
  "id": "MLC-T-CHM-007576",
  "term": "Morin transition",
  "field": "Chemistry",
  "definition": "A first-order magnetic phase transition observed in hematite (α-Fe₂O₃) where the orientation of antiferromagnetically coupled iron(III) ion spins changes. Above the transition temperature, the spins lie in the basal plane, resulting in a weak ferromagnetic moment, while below it, they align along the trigonal c-axis, and the material is purely antiferromagnetic. This spin-reorientation transition occurs at the Morin temperature, which is approximately 260 K for pure, bulk hematite.",
  "synonyms": [
    "spin-flop transition"
  ],
  "subject": "Inorganic Chemistry",
  "references": [
    "PAC, 1994, 66, 577. 'Definitions of terms relating to phase transitions of the solid state (IUPAC Recommendations 1994)' on page 587 (https://doi.org/10.1351/pac199466030577)"
  ],
  "url": "https://mlchart.com/terminology/chemistry/morin-transition/"
}