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 \div 1 \mu m$ at temperatures grater than the bulk Curie temperature by about $10^2$ K.