Enhancement of Magnetic Ordering by the Stress Fields of Grain Boundaries in Ferromagnets

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 the magnetization in a ferromagnetic film with grain boundaries is calculated. We found that 45° grain boundaries can produce long-range strain fields that result in a magnetic sheet along the boundary of width 0.5 ÷ 1 μm at temperatures higher than the bulk Curie temperature of about 10² K.