SPINMULTIFILM · Physical principles of the creation of novel SPINtronic materials on the base of MULTIlayered metal-oxide FILMs for magnetic sensors and MRAM

Physical principles of the creation of novel SPINtronic materials on thebase of MULTIlayered metal-oxide FILMs for magnetic sensors and MRAM

The main goal of the SPINMULTIFILM project is the development of novel nanoheterostructures (NHS) for future application as base elements of spintronic devices, first of all, magnetic field sensors (MFS) and magnetoresistive random-access memories (MRAM). The key research and technological aspects are focused on the formation of layers and/or nanosized grains of magnetic materials with a high degree of spin polarization. These layers/grains are separated by dielectric interlayers. The novel NHSs were designed according to two directions: (1) sputtering of multilayer films with dielectric interlayers and (2) deposition, on a substrate, of nanosized particles separated by dielectric shells. The action principle of these systems is based on tunneling magnetoresistance (TMR). The main idea of the project is based on the use of the Sr2FeMoO6 (SFMO) metal-oxide compound, having practically 100% spin polarization of conduction electrons, as a magnetic material for the formation of spintronic NHSs. The SFMO possesses high values of the Curie temperature (Тc = 400–460 K) and magnetoresistance (MR ~ 30–50%), high sensitivity to the magnetic field, good temperature and chemical stability. The main scientific results of the project are: 1. The use of mixtures of the SrFeO3 and SrMoO4 precursors instead of simple oxides allows the synthesis of the single-phase SFMO compound with a high degree of superstructural ordering of cations up to 87%. 2. The increase in the concentration of oxygen vacancies above δ ≥ 0.024 leads to the formation of an intermediate (Fe2+–Fe3+) valence state of iron. 3. The simultaneous presence in SFMO of magnetic regions of different magnetic nature was found. 4. NHSs with dielectric interlayers suitable for device application were created by two technologies accessible for small and medium enterprises: (i) sputtering of multilayer structures from targets and (ii) deposition of SFMO nanosized particles with subsequent oxidation of their surface by simple heat treatment. 5. The first approach was directed toward the formation of multilayered structures with a sequence of layer-by-layer deposited SFMO magnetic films and a separate deposition of dielectric layers (Al2O3) on platinized Si substrates. These technologies included pulsed DC sputtering, high-current pulse sputtering, and RF sputtering. 6. A technology of dielectric film deposition on top of SFMO layer by atomic layer deposition was developed. Dielectric Al2O3 interlayers with thicknesses of 3–7 nm were formed between the magnetic films by atomic layer deposition. 7. Mesa structures of the magnetic tunnel junction (MTJ) type were formed in the SFMO-based multilayers by photolithography and etching. Measurements of the electronic transport in these samples in a wide range of magnetic fields and temperatures are going on. 8. The second approach focused on single-layer magnetic films on a substrate. The structures exhibit low-field MR up to 300 K which opens the perspective of the creation of SFMO-based MRAM and MFS devices. 9. More than 60 seminars, knowledge exchange meetings and conference presentations were accomplished in physical and electronic formats. 51 scientific articles were published and are openly accessible to the public in journal format. 10. Young researchers have been trained in other beneficiaries’ laboratories where they had access to unique equipment and could learn modern research techniques and approaches.

Data: CORDIS, © European Union