GIANT MAGNETORESISTANCE AND CLUSTER-SIZE DISTRIBUTION IN Co/Ag GRANULAR MONOLAYERS

Abstract

In this paper, we report on granular Co/Ag monolayers grown by MBE on MgO(100). The clusters sizes and distribution are governed by nucleation and growth processes onto the surface. By a careful fitting of the giant magnetoresistance, using a Langevin formalism that relies solely on the number of Bohr’s magnetons in the superparamagnetic clusters, we infer their size distribution and its dependence on cobalt content. In Co 20 Ag 80, clusters sizes found range from 13 to 206 atoms, while in Co 60 Ag 40 they range from 40 to 3200, with the bigger clusters having sizes comparable to the total thickness of the samples. Also, by measuring the size of the effective clusters as function of temperature, we can estimate their blocking temperature and anisotropy constant.