Abstract:
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$^\circ$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.
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