Interdisciplinary Environmental Doctoral Studies "Physical, Chemical and Biophysical Foundations of Modern Technologies and Materials Engineering" (FCB) – PhD. Krzysztof Grochot
Project title
Interdisciplinary Environmental Doctoral Studies "Physical, Chemical and Biophysical Foundations of Modern Technologies and Materials Engineering" (FCB) – PhD. Krzysztof Grochot
Name of Beneficiary/Beneficiaries
Faculty of Physics and Applied Computer Science, the Stanisław Staszic AGH University of Science and Technology, Kraków
Name of programme
Operational Program Knowledge Education Development
Competition
Interdisciplinary Environmental Doctoral Studies "Physical, Chemical and Biophysical Foundations of Modern Technologies and Materials Engineering" (FCB)
Project value
PLN 10,123,883.00 for 75 beneficiaries
Funding value
PLN 134,895.00 per doctoral student
Project delivery period
from September 1, 2017 to August 31, 2022 (extended to October 31, 2023)
Get to know our team
See the effect of our work
Current Induced Magnetization Switching (CIMS) allows for energy-saving saving of bit states in hybrid multilayer systems. We studied the Dzyaloshinskii-Moriya interaction (DMI) and spin orbit torque (SOT) in the Ti(2)/Co(1)/Pt(0-4)/Co(1)/MgO(2)/Ti multilayer system (2) (numbers in brackets are the thicknesses of individual layers in nanometers) produced in the form of micrometer elements for measuring the Hall effect. In the tested system, a layer of heavy metal (Pt) is used as a source of spin current and as a non-magnetic spacer, the variable thickness of which enables optimal selection of the value of ferromagnetic interlayer coupling (IEC). Based on measurements of anomalous Hall effect (AHE), anisotropic magnetoresistance (AMR) and spin Hall magnetoresistance (SMR) signals, we found that an increase in Pt thickness (tPt) leads to a reorientation of the magnetization direction of ferromagnetic Co from an in-plane direction to a direction perpendicular to the plane layers at tPt ≈ 1.3 nm. A further increase in the Pt thickness, above 3 nm, leads to a significant decrease in the coupling value and, as a consequence, the two weakly coupled Co layers become magnetized orthogonally to each other. Based on the analysis of the spectra of the Stokes and anti-Stokes peaks, measured using the Brillouin light scattering (BLS) method, the value of the effective DMI constant as a function of the Pt spacer thickness was determined. This value reaches its highest value for a Pt thickness of approximately 2 nm, where the perpendicular anisotropy is the highest. Imaging of magnetic domains using Kerr microscopy showed skyrmion domains in the strong coupling region, which decay as the ferromagnetic coupling decreases. Finally, we investigated the effect of SOT-CIMS, which we analyzed theoretically using the Landau-Lifshitz-Gilbert-Slonczewski equation. As a result of the asymmetry of the Co/Pt and Pt/Co interfaces, IEC and the DMI interaction, we obtained multi-level magnetization current switching, a very important phenomenon in SOT-MRAM applications.
What problem does our project solve?
The development of new technologies for storing and processing information based on electron spin arouses wide interest from the point of view of potential applications in the area of energy-saving electronic memories consistent with the trend of green information technology (Green IT). The doctoral thesis concerns research on thin-film heterostructures of spin electronics (so-called spintronics) characterized by high efficiency in generating lossless spin currents. For this reason, the results obtained during the doctoral thesis are very interesting for applications in electronics, in particular in computer technology in the field of information storage and processing. This applies primarily to new solutions in the field of operating memory of Magnetoresistive Random Access Memory (MRAM) type.
Moreover, the effect of spin-orbit torque (SOT - Spin Orbit Torque) on the magnetization of the ferro-magnetic layer using spin-polarized current is used in logic systems and microwave oscillators used in telecommunications. We show that savings in energy consumption by spin electronics components are possible if the contribution of the spin current prevails over the charge current, which is the source of energy loss. The doctoral thesis analyzed theoretically and experimentally examined the SOT phenomenon excited by a spin-polarized current. The most important research results were published in highly indexed journals on the Journal Citation Reports (JCR) list and were presented at national and international conferences. We believe that our research will primarily contribute to the fact that common smartphones, tablets and computers, thanks to the built-in spintronic elements, will consume less energy than those currently produced.
Who will benefit from the project results?
The basic result of the research of the doctoral thesis "Spin magnetoresistance and spin Hall effect in thin-film hybrid systems: heavy metal, ferromagnetic, antiferromagnetic" is the material optimization of the multilayer system in terms of spin-orbit interactions and the generation of spin-polarized current needed for multi-state switching of digitally encoded magnetization in memory cells SOT-MRAM. An example is a joint publication with the company Singulus Technologies https://www.singulus.com/products/semiconductor-cluster-tools/, published in IEEE Transactions on Electron Devices, vol. 68, no. 12, 6379-6385 (2021), DOI: 10.1109/TED.2021.3122999 "Angular Harmonic Hall Voltage and Magnetoresistance Measurements of Pt/FeCoB and Pt-Ti/FeCoB Bilayers for Spin Hall Conductivity Determination." The works published as part of the doctoral thesis have been noticed in the international spintronics community and have been cited many times.
Our advice to other Applicants
The ongoing project titled Interdisciplinary Environmental Doctoral Studies "Physical, Chemical and Biophysical Foundations of Modern Technologies and Materials Engineering" (FCB) undoubtedly gave its beneficiaries great opportunities for multidisciplinary scientific development and implementation of research plans through the possibility of financing trips for internships abroad and taking part in a number of national and international scientific conferences. The funds allocated for publications in Open Access journals gave doctoral students the opportunity to make their research results public and easily disseminate them in the international scientific community.