Magnetic Anisotropy Dispersion in FeCo Films

We report on our study of magnetic and nonmagnetic parameters such as coercivity, anisotropy , magnetic dispersion, and stress on FeCo films of various thicknesses from 25 A to 500 A . We used 10 A Ru or NiFe seed layers for two sets of FeCo films. All films showed so-called hard-axis coercivity rocking, i.e., the hard-axis coercivity exhibits two local minima close to the nominal hard axis. Magnetic properties and stress change dramatically with FeCo thickness, but with little difference between the two types of seed materials. We found a correlation between the angular separation of the two local coercivity minima and easy-axis coercivity. The results stress the need to differentiate between two levels of dispersion, one at the microscopic and the other at the macroscopic level.