Exchange bias in a superspin glass system of Co particles in Mn matrix

The magnetic properties of 1.8 nm Co particles dispersed ( 4.7% volume fraction) in a Mn matrix have been investigated. The results show that the antiferromagnetic matrix provides a strong interface exchange coupling with the ferromagnetic particles and, through it, an effective long range interparticle correlation. This gives rise to a superspin glass type freezing ( T-g = 62 K), exchange bias and a remarkable enhancement of thermal stability with respect to the same particles in a Ag matrix, as shown by a shift of the distribution of energy barriers and switching fields to much larger values.