Magnetic interactions in Fe films sputtered on nanochannel alumina

We present in this work a study of the magnetic interactions observed in Fe films sputtered onto the surface of commercial porous nanochannel alumina. These films, which grow in a "network-like" structure, have been characterized by delta M plots, magnetic viscosity and activation volume as a function of film thickness (5 nm/spl les//spl phi//spl les/100 nm) and substrate pore size (20 nm, 100 nm and 200 nm average diameter). We have found a maximum in the remanent coercivity and a minimum in the interparticle interaction for a film thickness /spl phi//spl sim/20 nm for the three substrates. The behavior of the magnetic viscosity and the activation volume on the other hand is dependent on the pore size. We have interpreted our results in terms of the different porosity of the substrates, As the porosity is smaller for the substrates with smaller holes, the continuous film behavior is approached first because the pores fill in more rapidly.