Change in the magnetic properties of polycrystalline thin-film magnetite upon introduction of an iron sublayer

The field dependences of the magnetic moment of polycrystalline magnetite films formed by pulsed laser deposition on a silicon substrate with the addition of an iron sublayer have been investigated. The influence of the sequence of layers Fe/Fe 3 O 4 and Fe 3 O 4 /Fe on the magnetic characteristics of these structures has been analyzed. It has turned out that an increase in the saturation magnetization and the formation of a rectangular hysteresis loop with the coercive force acceptable for applications of thin-film magnetite as a hard magnetic electrode of the magnetic tunnel junction are observed only for the sequence of layers Fe/Fe 3 O 4 . The effect of the vacuum annealing temperature on the magnetic properties of polycrystalline samples of the Fe/Fe 3 O 4 structure has been studied. It has been found that the best result is achieved at an annealing temperature of 500°C. The phenomenological model describing the magnetic properties of the polycrystalline two-layer magnetic structure Fe/Fe 3 O 4 has been formulated. The results of numerical calculations have demonstrated that the introduction of only two phenomenological anisotropic interactions into the expression for the energy of the film provides a qualitative description of the observed experimental data in the form of hysteresis loops.