The new concepts offered by “spinorbitronics” make it possible to envisage more frugal electronics. In particular, for writing a magnetic memory (MRAM), a new concept of magnetization reversal by a spin-orbit couple is emerging. Its principle permits a significant decrease in memory writing energy and enhanced endurance. Its operation is based on the conversion of a charge current in a material with strong spin-orbit coupling into a spin current that is absorbed by the adjacent magnetic layer to be reversed (and which stores the 0 or 1 information). The higher the charge-spin conversion efficiency, the lower the current to be applied to reverse the magnetization, thus reducing energy consumption.
The objective of the thesis project is to maximize this conversion by developing and implementing new materials, 3D topological insulators (TI). Indeed, it has been demonstrated recently that the charge-spin conversion was very strong in these materials thanks to the strong spin-orbit coupling and the existence of topological surface states in which it is possible to produce a strong spin accumulation thanks to an electric current. In this context, LETI is interested in the growth by sputtering of this type of materials on large surfaces. These are specifically bismuth and antimony tellurides (Bi2-x SbxTe3). In parallel, SPINTEC is actively involved in the study of spin-orbit torque, with extensive expertise in deposition and control of ferromagnetic layers, as well as measurement of spin-orbit torques that cause magnetization reversal. The aim of this thesis project is therefore to combine LETI’s know-how on IT growth and SPINTEC’s expertise on ferromagnetic materials and spin-orbit torques. A thesis is currently underway at LETI on the development of Bi2-x SbxTe3 films on industrial sputtering growth equipment. The goal of the proposed thesis project is to combine different x compositions of the Bi2-x SbxTe3 alloy with various FM ferromagnetic materials (CoFeB, CoFe, Co, Fe) to optimize these TI/FM couples and thus qualify these materials for their use in MRAM.