Structure of Grain Boundaries in Oxides.
Abstract
The magnetic properties of sintered alpha-ferric oxide were investigated as a function of grain size for three different kinds of powders. The coercive force was found to change drastically as soon as grain boundaries were formed by sintering, while the Morin temperature and the antiferromagnetic susceptibility were unaffected. The increase of magnetic hardness was identified as an effect of grain boundaries rather than the effect of crystal size only. The existence of grain boundaries appeared to be equivalent to the existence of strong uniaxial anisotropy of the order of 1000 ergs per g in the vicinity of grain boundary which could be visualized as a film possessing strong uniaxial anisotropy. The microscopic origin of the strong uniaxial anisotropy associated with grain boundaries is discussed on the basis of the dislocation structure of the grain boundary. The lowering of six fold symmetry of the crystal to two fold symmetry due to dislocations is suggested as the origin of this uniaxiality. (Modified author abstract)
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1973
- Accession Number
- AD0776069
Entities
People
- G. C. Kuczynski
Organizations
- University of Notre Dame