Enhancement of magnetic ordering by the stress fields of grain boundaries in ferromagnets

In the paper we predict a distinctive change of magnetic properties and considerable increase of the Curie temperature caused by the strain fields of grain boundaries in ferromagnetic films. It is shown that a sheet of spontaneous magnetization may arise along a grain boundary at temperatures greater than the bulk Curie temperature. The temperature dependence and space distribution of magnetization in a ferromagnetic film with grain boundaries are calculated. We found that ${45}^{\circ }$ grain boundaries can produce long-range strain fields that results in the width of the magnetic sheet along the boundary of the order of $0.5÷1\mu m$ at temperatures grater than the bulk Curie temperature by about ${10}^2$ K.