Solitary magnetic inhomogeneities in a thin ferromagnetic film

Abstract

It is known that in theoretical investigation of the domain structure in infinite ferromagnetic samples with a mixed anisotropy there appear solutions corre� sponding to 0° domain walls (DWs) of the Bloch or Neel type [1]. The calculations performed show that such DWs are quite suitable model representations of magnetic inhomogeneities formed in crystal defects, which makes it possible to study processes of spin reorientation in realistic magnets. However, it is by no means all experimentally observed aspects of the wall nucleation [2] that can be investigated theoretically in view of the “rigidity” of the model under consider� ation. One of the ways of the expansion of the field of application of this model is taking into account the effect of the finite thickness of the film on the structure of 0° DWs. Note that earlier no similar investigations were performed by analytical methods because of the complexity of the analysis of nonlinear integrodiffer� ential equations that describe the distribution of mag� netization in samples of finite dimensions. However, for the case of 0° DWs such an analysis can be per� formed in a nontrivial way using the perturbation the� ory. To this end, let us determine the demagnetizing fields caused by the geometry of the sample. They are found from the equations of magnetostatics [3]; in the case of an arbitrary distribution of magnetization M(r) in space, their strength can be represented as follows: