ANTIFERROMAGNETIC TRANSITION-TEMPERATURE OF MNO ULTRAFINE PARTICLE

The size dependence of Neel temperature T-N Of MnO ultrafine particles in LiF matrix with the average size range from 4.0 nm to 5.4 nm was i nvestigated through the temperature dependence of the ESR linewidth. I t was found that the TN Of MnO ultrafine particles becomes smaller tha n that in bulk state, and decreases as the size becomes smaller. The f act is mainly attributed to the smallness of the coordination number o f surface atom in a particle. This tendency is also confirmed by the c alculation of using mean held approximation of the Ising clusters.