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

Project Information

SPINMULTIFILM

Grant agreement ID: 778308

DOI

10.3030/778308

Project closed

EC signature date 22 November 2017

Start date 1 January 2018

End date 30 June 2023

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 436 500,00

EU contribution

€ 436 500,00

Coordinated by

UNIVERSIDADE DE AVEIRO
Portugal

Periodic Reporting for period 2 - SPINMULTIFILM (Physical principles of the creation of novel SPINtronic materials on thebase of MULTIlayered metal-oxide FILMs for magnetic sensors and MRAM)

Reporting period: 2020-01-01 to 2023-06-30

Summary of the context and overall objectives of the project

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.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

Dense, homogeneous single-phase Sr2FeMoO6-δ targets for layer deposition with a controlled superstructural ordering of the Fe/Mo cations have been obtained. The SFMO targets were obtained under conditions of control over oxygen exchange processes, with an increased degree of cation ordering, reduced economic costs, a simplification of technological equipment and a decrease in environmentally harmful emissions.

For the first time, Sr(2-y)Fe(1+x)Mo(1-x)O(6-δ) thin films were deposited by direct synthesis in a sputtering process driven in the oxide mode onto pure, oxidized and platinized 150 mm silicon wafers.

The formation of single-layer films on the base of the SFMO sol-gel nanopowders with dielectric shells has been carried out by a single-step process.

The deposition of SFMO/Al2O3/SFMO multilayer heterostructures using the reactive ion beam sputtering has been successfully performed. Crystal structure, phase and element compositions of the “magnetic-dielectric” multilayer films were controlled after each stage of the sequential sputtering, which has made it possible to optimize their formation processes.

Photolithography and etching of the obtained Platinized Si / SFMO / Al2O3 / CoFe / Ag multilayers were performed. As a result, mesa structures with an elliptical cross-section and dimensions of 4x2, 6x3, 8x4 and 10x5 μm were formed. These samples have a basic structure of magnetic tunnel junctions (MTJ) employed as MRAM and magnetic field sensors. The electrical transport measurements on these samples in a wide range of temperatures and magnetic fields are going on.

The resistivity and MR behaviour of the granular Sr2FeMoO6 material with dielectric SrMoO4 interlayers has been studied in a wide temperature and magnetic field range.

The project’s results have been published in peer-reviewed journals and made available to the scientific community and general public by using a scientific repository. The knowledge generated in the Project has also been regularly communicated by means of seminars and attendance of conferences/workshops, as well as regular meetings between Consortium members.

The project’s website and associated social media (Facebook, Twitter and LinkedIn) were created with the intent of publicising the project and its activities but also serving the purpose of providing outreach knowledge for the general public. All pages were updated on a regular basis and will continue to be even beyond the end of the project to help disseminate the knowledge generated.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The following technological and socio-economic progress is expected:
1. Science and technology - development of reliable and low-cost technologies of new materials (SFMO and related compounds) with required structural, electrical, magnetic and magnetoresistive characteristics.
2. Automotive industry – creation of scientific and technological foundations of new MFSs for protective and security systems.
3. Electronic industry - creation of the scientific and technological foundations for a new generation of magnetic random access memory (MRAM) and highly sensitive magnetic sensors.
4. Socio-economic impact – training of highly qualified young researchers who will work in European institutes and enterprises.

The SPINMULTIFILM project deepens essential aspects of the manufacture of SFMO-based MTJs. Modern artificial intelligence (AI) text generators such as ChatGPT are based on neural networks. The conventional CMOS neuron and synapse designs require numerous transistors and feedback mechanisms and would be unsuitable for developing modern AI systems. The main advantage of spintronic devices compared to other resistive memories for neuromorphic computing is the possibility to induce complex and tunable resistance dynamics through spin torque. AI has the potential to bring about numerous positive changes in society, including enhanced productivity, improved healthcare, and increased access to education.

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