Interactions between regions within magnetic film

Calculations are made on a model of a ferromagnetic film in which interactions between regions enter as a perturbation of the configuration without interactions. Nine regions are assumed with a uniform dispersion of uniaxial anisotropy axes through 0.16 radians and with no magnitude dispersion. The energy of interaction between any two regions is taken to be
-NM_{1} \cdot M_{2}
and values of the relative interaction field,
h_{i} = 2NM/H_{k}
, which are studied, are 0.0, 0.05, 0.1, and 0.3. Calculations are made corresponding to torque and magnetoresistance measurements. The field variation is a rotation in the film plane with constant magnitude. Values chosen for
h = H/H_{k}
range from 0.1 through 1.1. The representation of magnetoresistance values as certesian coordinates is shown to be very revealing of the effects of interactions. In the presence of interactions it is found that irreversible, rotational switching of the local magnetization is through smaller angles than with no interactions; this causes the appearance of locked regions.