Effect of thickness on structural and magnetic properties in nanocrystalline Fe-N thin films

We have investigated the structural and magnetic properties of Fe-N thin films, for a thickness range of 40-280 nm, grown on Si(100) substrates. The Fe-N films exhibit a structural transformation from ε-Fe3N phase to γ′-Fe4N phase with the increasing film thickness. The average grain size and saturation magnetization are found to increase with the increasing thickness. The smaller Fe-N grains and large strain inhibit more the domain wall motion and, therefore, the films exhibit an increase in coercivity with the decreasing thickness. The influence of structural properties, such as crystallographic phase, crystallite size, and surface roughness on the magnetic properties of saturation magnetization and coercivity, is demonstrated as a function of the film thickness. © 2013 Elsevier B.V. All rights reserved.