HOPKINSON EFFECT STUDY IN SPINEL AND HEXAGONAL FERRITES

The magnetic susceptibility shows a Hopkinson peak just below the Curie temperature TC when heating the selected hexagonal and spinel ferrite samples. It is proposed that this peak can be associated with a transition from stable magnetic state to super-paramagnetic relaxation above the blocking temperature up to the TC . The Hopkinson effect results are compared with SEM micrographs of both studied hexagonal and spinel ferrites. K e y w o r d s: Hopkinson effect, super-paramagnetic relaxation, blocking temperature, spinel and hexagonal ferrite