  The magnetic easy axis orientation was studied by the third order perturbed
Heisenberg Hamiltonian. Ferromagnetic CoPt/AlN multilayer thin films with
number of layers N=11, 16 and 21 synthesized on fused quartz substrates using
dc magnetron sputtering technique have been employed as experimental data.
According to experimental research performed by some other researchers, easy
axis of these fcc structured ferromagnetic films is oriented in the plane of
the film at one particular temperature. Average value of out of plane spin
component was plotted against temperature in order to determine the spin
reorientation temperature. The spin reorientation temperature was highly
sensitive to 2nd order magnetic anisotropy constant.
