Epitaxial Growth of Complex Metal Oxides

6.2. Magnetism and major magnetic-oxide systems

6.2.1. Magnetism in oxides

Magnetic materials violate time-reversal symmetry, but are invariant under spatial inversion; in other words, when magnetic moments are present in a crystal, the antisymmetry operator must also be present. The 32 classical crystallographic point groups do not have the antisymmetry operator and hence cannot fully describe the symmetry of magnetic crystals. Symmetry analysis reveals 122 total magnetic space groups of which only 31 can support ferromagnetism (Aizu, 1970; Laughlin, Willard, & McHenry, 2000). A material is said to be a ferromagnet when there is long-range, parallel alignment of the atomic moments resulting in a spontaneous net magnetization even in the absence ...