Ferrimagnetic magnetite, Fe₃O₄, is a promising material for spin dependent electronics due to high Curie temperature (of 858 K) and high degree of spin polarized carriers at room temperature. Up to now, high quality Fe₃O₄ films have been grown heteroepitaxially on latticed-matched MgO, SrTiO₃ and Al₂O₃. However, for most applications such as tunneling magnetoresistance (TMR) devices there is great interest in various heterostructures composed of lattice-matched ferromagnetic, antiferromagnetic films, highly conducting underlayers and insulating barrier layers.

In this work, Fe₃O₄ thin films were grown on both lattice matched MgO or Al₂O₃ substrates and La_2/3A_1/3MnO₃ (A = Ca, Sr, Ce) underlayers by DC magnetron sputtering of metallic Fe target under a fixed Ar:O₂ (30:1) gas mixture pressure of about 5 Pa. The manganite films were prepared by the same method on both lattice-matched SrTiO₃ and NdGaO₃ buffered by highly conductive LaNiO₃ or RuO₂ layers. Crystalline structure of all the films and heterostructures were characterized by x-ray difraction (XRD) and reflected high-energy electron diffraction (RHEED). The electrical resistance, magnetoresistance and voltage versus current were measured for the films and multilayer structures in a wide range of temperatures and magnetic fields. Three point-probe method was applied to investigate the interface resistance and tunneling magnetoresistance of the heterostructures. Electrical properties of the interfaces were modelled to elucidate the effect of deposition conditions and possible oxygen diffusion at various interfaces.

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