On the coupling between double Ni-Fe films

An experimental method is described which may be used to determine the shape of the coupling energy curve between the layers in double films. The coupling energy, assumed here to be isotropic, is an additional energy term in the total energy expression. A simple formula is derived for the derivative of the coupling energy with respect to the angle a between the magnetizations in both layers. Experimental data for measurements of the reversible susceptibility permit the determination of the angle α from another equation. It is found that the shape of the coupling energy curve differs from , and it seems that the formula for this energy is more complicated and probably includes the exchange energy as well.