We plan to study the growth and the magneto-transport properties of ferrite-based spintronics devices. The insulating ferrites are a family of mixed oxides with the general formula AFe2O4 (A= Co, Ni, Mn ?). These ferrimagnetic oxides are very attractive for applications in spintronics because these materials have a high Curie temperature with the capability of spin filtering effect. So a strongly spin-polarized current can be generated and the use of ferrites in magnetic tunnel junctions can lead to high tunnelling magnetoresistance effects (TMR) at room temperature. The SPCSI team is specialized in the epitaxial growth of oxide-based magnetic heterostructures by molecular beam epitaxy (MBE) and we have recently obtained promising results in CoFe2O4 or MnFe2O4-based magnetic tunnel junctions.

The aim of this thesis will consist to perform the growth of high quality ferrite ultra-thin layers by molecular beam epitaxy (MBE), as well the demonstration of their spin filtering capabilities and to develop a new variant of ferrite-based spin-filters, the so called double spin-filters. In these heterostructures, constituted of two ferrimagnetic barriers, AFe2O4/BFe2O4, the amplitude of the TMR depends only on the intrinsic characteristics of the two barriers and resistance variation as large as 105% can be expected.