Title :
Aging phenomena in cobalt-modified iron oxides: influence of dilution and magnetic interactions
Author :
Schwab, E. ; Veitch, R.J.
Author_Institution :
BASF Aktiengesellschaft, Ludwigshafen, West Germany
fDate :
9/1/1989 12:00:00 AM
Abstract :
Aging of cobalt-modified iron oxides is shown to lead to changes of the coercivity of the particles. Microscopically, this is due to variations in the local structure of the cobalt ferrite surface layer under the influence of magnetic interactions with neighboring particles. By means of dilution with nonmagnetic material these interactions can be reduced and, consequently, in these diluted samples no aging is observed. Aging is dependent upon the topography of the surface layer. In contrast to the above-mentioned smooth particles, pigments with very rough surfaces do not show aging effects. This is interpreted as being due to very large stray fields in the rough surface layers which mask the additional effect of particle interactions
Keywords :
ageing; cobalt compounds; coercive force; iron compounds; magnetic properties of fine particles; Co-Fe2O3; Fe2O3; aging; coercivity; dilution; ferrite surface layer; magnetic interactions; particle interactions; rough surfaces; stray fields; topography; Aging; Cobalt; Coercive force; Ferrites; Iron; Lead compounds; Magnetic force microscopy; Rough surfaces; Surface roughness; Surface topography;
Journal_Title :
Magnetics, IEEE Transactions on