Magnetic properties and structure of Al/Fe‐N periodic multilayer thin films

Periodic multilayer thin films of the form (xAl/yFe‐N)n were grown by sequential dc‐magnetron sputtering. The thicknesses of the individual Al and Fe‐N layers are given by x and y, respectively, and the total number of bilayer units is n. For this set of experiments, x was fixed at 3.5 nm and y was varied systematically from 3 to 135 nm. Magnetic properties were studied by vibrating sample magnetometry and crystal structure by x‐ray diffraction for both as‐deposited and annealed films. A strong enhancement of the saturation magnetization was found in multilayers containing the thinnest Fe‐N layers which was further strengthened by annealing. The coercivity was found to decline monotonically with decreasing Fe‐N layer thickness in the as‐deposited films. Annealing produced nonsystematic changes in coercivity. The evolution of magnetic properties with decreasing Fe‐N layer thickness was correlated with complex changes in iron‐nitride crystal structure. For the thinnest layers of Fe‐N (less than 12 nm) the m...