Growth of epitaxial ferromagnetic thin films on semiconductor substrates and their applications

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Recent progressf epitxial growth technology has made it possible to prepare a variety of new artificial thin films and heterostructures (HS's) consisting of dissimilar materials. Among them, stable epitaxial ferromagnet/semiconductor HS's offer unprecedented opportunities for basic and applied research, adding a new degree of freedom inmaterials design. We have performed a series of studies on epitaxial growth and physical properties of such novel dissimilar heterostructures with focus on ferromagnetic compound/semiconductor systems. Here we used both Si and GaAs as semiconductor saubstrates. We have successfully grown epitaxial ferromagnetic MnAs thin films on GaAs (001) and (111) B,and on Si (001) and (111) substrates, by using molecular beam epitaxy (MBE). Our original template approaches are found to be very effective to obtain high-quality epitaxial films in such heteroepitaxy of dissimilar materials, and also to control magnetic anisotropy of the ferromagnetic films. Furthermore, we have successfully grown MnAs/GaAs/MnAs ferromagnet-semiconductor trilayr heterostructures on GaAs (111) B and S (111) substrates by MBE.These new HSs are promising for future applications to magnetic nonvolitile memory devices and/or magnetic field sensors coupled with underlying Si and/or III-V semiconducror electronic/optical circuitry.