Magnetic Domain Structure of Hematite

Abstract

Magnetic colloid observations on synthetic hematite indicate the existence of only two phase domain structures. The normal or N structure is a usually slablike 180° wall structure where the majority of walls are parallel to the basal plane and have a 100–200 μm separation. Wall energies are estimated to be 0.35 × 10−1 to 1.0 × 10−1 erg/cm2 from domain geometry. Under special circumstances, a domain structure, called CN domains, occurs in [Formula: see text] and [Formula: see text] surfaces and appears to be a two phase structure of non-180° walls. Spontaneous magnetostriction requires these walls of 100–200 μm separation to be planar and lie either perpendicular to or at ~26° to the basal plane. A third structure, called C domains, of 25–50 μm spaced planar walls occurs on (110) surfaces in two characteristic directions symmetric with the basal plane and consistent with CN-wall geometry. However, because of their behavior and geometry, they appear to be nonmagnetically stabilized but possibly by a strain effect. By using magnetoelastic coupling for the effective basal plane anisotropy constant for moment rotation in domain walls, N-wall energies are estimated to be 0.45 × 10−1 to 1.0 × 10−1 erg/cm2. Because of geometry complications CN-wall energies are difficult to calculate but are estimated to be ~10−1 erg/cm2 or slightly larger.