Magnetization processes in a dot of ferrimagnetic garnet near the compensation temperature
Résumé
At the compensation temperature of ferrimagnetic materials, magnetization vanishes but domain wall energy does not. Magnetic domains and coercive field become then very large. We are interested in small objects of such materials, in order to study the effect of size, shape, edges... on the domain structure and on the magnetization processes. A magnetic garnet film was patterned by chemical etching, leading to dots 7 μm thick and 10 to 100 μm wide. Domain observations were performed close to compensation (213 K) under magnetic field up to 22 mT. In the case where the dots are connected by a thin continuous magnetic film (partial etching), magnetization reversal occurs via an intermediate spin-flop state, coexisting with perpendicular domains. In order to analyze this process, we performed a mean field computation to characterize the spin-flop state itself, by the amplitude and orientation of the magnetization of each sublattice.