Ongoing Research Projects

From Interfaces to Interlayers: The Next Frontier of Chiral Magnetism

Advancing spintronics beyond current limits requires harnessing emergent magnetic phenomena enabling new device functionalities. The recently discovered interlayer Dzyaloshinskii-Moriya interaction (IL-DMI) offers unexplored opportunities for three-dimensional spin texture engineering and deterministic magnetization control in synthetic antiferromagnets. Despite recent progress, critical challenges persist: IL-DMI magnitude remains substantially weaker than symmetric RKKY coupling, preventing robust chiral texture emergence; field-free spin-orbit torque switching suffers from high critical currents and poorly understood dynamics; and direct visualization of IL-DMI-induced three-dimensional configurations remains elusive. This project addresses these challenges through systematic investigation combining atomic-precision materials synthesis, device implementation, and advanced characterization. Theoretical studies predict that chiral interlayer coupling emerges from controlled symmetry breaking at ferromagnet/spacer interfaces combined with spacer electronic structure contributions. Our hypothesis is that molecular beam epitaxy’s atomic-layer precision enables experimental validation and deterministic control of these mechanisms by systematically tuning growth conditions, interface chemistry, and spacer thickness.

Grant financed by the Polish National Science Centre (NCN)
Programme: OPUS 30
Budget: 2 020 320 PLN

Antiferromagnetic insulatronics – from fundamental properties to multi-level allelectric spintronics

While engineering of magnetic anisotropy in ferromagnets (FMs) has been so far intensively studied, the control of antiferromagnets is nowadays in focus of magnetism community and the aim of contemporary AFM spintronics is to replace ferromagnets in the active components of electronic devices. Antiferromagnets, which possess a zero net magnetic moment, up to very recently have played a minor role, for example in the spin-valve effect by stabilizing the direction of FM reference layer via an exchange bias effect. However, recent demonstration of manipulation of the magnetic states in AFMs makes them a promising alternative for use as active elements in the next generation data storage materials. In contrast to FMs, the AFMs are robust against magnetic perturbations and do not create stray fields, which is beneficial for ultimate down-size scalability of magnetic memory devices. Manipulation of the Néel vector in AFMs was realized via magnetic, strain, electrical and optical methods. For AFM insulators electrical switching of the Néel order can be realized in heavy metal(HM)/AFM bilayer, where a charge current in the HM layer induces a transverse spin current via the spin Hall effect and creates a spin-orbit torques (SOTs) in AFM. Recently electrical switching of the Néel order was demonstrated via spin Hall magnetoresistance measurements in NiO/Pt , CoO/Pt and Pt/α-Fe2O3 systems. For NiO(001)/Pt and CoO(001)/Pt electrical switching of bistate AFM moments, while for Pt/α-Fe2O3 observation of tristate switching was reported. The nature of the present project is two-fold. First, we aim to follow the fundamental magnetic properties of IAFM1/IAFM2 bilayers. By tuning the choice of the substrate, buffer and covering layers as well as thickness of particular AFM sub-layers, the symmetry of the in-plane magnetic anisotropy of the individual AFM components and overall antiferromagnetic system will be engineered. Besides such stricte fundamental project aspects, the development of a unique state-of-art technology by integrating into one memory cell two antiferromagnetic layers will enable an important progress in antiferromagnetic spintronics. This idea, if successful, will provide a prototype of a novel multilevel AFM-based magnetic memory that enables to push further data density. Specifically, in our experiments we will switch independently the Néel order in each AFM layer in AFM bilayers stack that should result even in six or more different values of Hall resistance. The exact number of resistance states will be determined by anisotropy of each AFM layer and relative orientation of easy axis of top and bottom AFM layers which makes proposed fundamental studies not only important for the basic knowledge but also crucial for magnetotransport properties and thus for spintronic applications.

Grant No. 2021/41/B/ST5/01149 financed by the Polish National Science Centre (NCN)
Programme: OPUS 21
Project duration: 17.01.2022 – present
Budget: 1 462 780 PLN

Piezospintronics and voltage control of magnetic anisotropy – novel approaches to control magnetic state of antiferromagnets

Antiferromagnets (AFMs), which possess a zero net magnetic moment, up to very recently has played a passive role in spintronics. However, recent demonstration of manipulation of the magnetic states in AFMs makes them a promising alternative for use as active elements in the next generation data storage materials. In contrast to FMs, the AFMs are robust against magnetic perturbations and do not create stray fields, which is beneficial for ultimate down-size scalability of magnetic memory devices.
The aim of the project is to control magnetic state of thin antiferromagnetic films with a use of electric field. The project will be realized in two parallel paths. The first will concentrate on strain-induced piezoelectric switching of magnetic moments in AFMs. Here, we will grow metallic and insulating thin antiferromagnetic films on piezoelectric PMN-PT substrates and examine how the electric field applied to the substrate influence the magnetic state of AFM through magnetoelastic coupling. For metallic AFMs we will explore effect of modification of the spin-orbit interaction on the electrical switching characteristics.
The second path of the project focuses on demonstration of direct influence of electric field on magnetic anisotropy in AFMs, so called voltage control magnetic anisotropy (VCMA) effect. In this case an electric field will be applied directly to the AFM/dielectric interface. In both routes AFM layers will be grown by molecular beam epitaxy which offers a superior control of the interface and enables to grow the layers with sub-nanometer thicknesses. With a use of sophisticated techniques, like x-ray linear magnetic dichroism and x-ray photoemission electron microscope we will be able to characterize magnetic structure of AFMs and its dependence on (piezo-)-electric field induced switching. The feasibility of AFM piezospintronics and voltage control of magnetic anisotropy in AFMs will be presented via magnetotransport measurements.

Grant No. 2020/38/E/ST3/00086 financed by the Polish National Science Centre (NCN)
Programme: SONATA BIS 10
Project duration: 29.07.2021 – present
Budget: 1 514 000 PLN

Previous Research Projects

Antiferromagnetic proximity effect and development of epitaxial bimetallic antiferromagnets – two routes towards next-generation spintronics

The main active components of spintronic elements are ferromagnets (FMs), in which a net spin polarization is responsible for logical zeros and ones. Antiferromagnets (AFMs), in which magnetic order is accompanied by a zero net magnetic moment, play an important role in the spin-valve effect by establishing direction of FM reference layer via an exchange bias effect. However, recent demonstration of magneto-transport effects in AFMs and their ultrafast magnetization dynamics make them potential candidates that could replace FMs in spintronic devices. In this project I propose two routes that will lead to development of antiferromagnetic spintronics. The first one is focused on tuning magnetic properties of AFMs via modulation of strain in AFM layer. The second path concentrates on the epitaxial bimetallic AFMs. In both paths the feasibility of AFM spintronics with studied AFM materials will be presented.

Financed by the Foundation for Polish Science (FNP)
Programme: FNP HOMING
Project duration: 01.03.2018 – 28.02.2021
Budget: 787 310 PLN
https://www.afm-homing.agh.edu.pl/home

Tunable magnetic properties of spintronic nanostructures based on FeRh alloy

Ferromagnets(FM) are materials that exhibit spontaneous magnetization due to the fact that magnetic moments of the atoms are parallel to each other. In contrast in the antiferromagnetic (AF) materials the moments of neighboring atoms are antiparallel and cancel each other, therefore antiferromagnets does not display magnetization. The mechanism that is responsible for the ordering of atomic moments in both ferro- and antiferromagnets is known as the exchange interaction. Usually, with increasing temperature both ferromagnetic and antiferromagnetic ordering get weaker and finally disappear above the critical temperature namely: Curie temperature and Neel temperature for the ferromagnets and antiferromagnets respectively. At 1938, for equi-atomic FeRh alloy with cesium-chloride structure, intriguing transformation of magnetic properties was observed that consists in appearance of ferromagnetism and simultaneous disappearance of antiferromagnetism with increasing temperature. The FeRh alloy undergoes a transition from the antiferromagnetic state to ferromagnetic state (AFM›FM transition) at the temperature of about 370K, which apparently is opposite tendency to a common weakening of ferromagnetism with increasing temperature. The goal of the project is to utilize transformation of magnetic properties accompanying AFM›FM transition characteristic for FeRh alloy films in tailoring of magnetic properties of thin ferromagnetic films that are in a direct contact with FeRh system. The transfer of changes of magnetic properties accompanying AFM›FM transition in FeRh layers to the neighboring FM films is provided by the exchange interaction existing at the interface. Such “glued” together layers of ferromagnetic material and FeRh alloy can be obtained by their subsequent deposition onto the appropriate substrate. Resulting bi-layer FM/FeRh system will display a strong changes of magnetic properties occurring with increasing temperature, originating from the AFM›FM transition in FeRh sublayer. Hence the new magnetic properties of this artificial FM/FeRh system can be expected with respect to magnetic properties of ferromagnets and FeRh alloy alone, being tunable by variation of temperature. The concept of bilayer FM/FeRh with tunable magnetic properties will be further developed by implementation of FM/FeRh bilayers into a more complex multilayer systems. The manipulation with the magnetic state of FM/FeRh system embedded in such multilayers will allow for the control of magnetic state of the whole multilayer and also its electrical resistance in a similar way as it happens in sandwiches exhibiting famous giant or tunneling magnetoresistance phenomena.

Grant No. 2015/19/B/ST3/00543 financed by the Polish National Science Centre (NCN)
Programme: OPUS 10
Project duration: 03.10.2016 – 02.10.2020
Budget: 1 114 000 PLN

Cooperation

Elettra Sincrotrone Trieste

The close cooperation between the AGH team and the researchers responsible for the Nanospectroscopy beamline at Elettra Sincrotrone Trieste has enabled a continuous exchange of expertise in synchrotron-based PEEM methods. In particular, the extensive experience of the Trieste group in X-PEEM microscopy strongly complements our expertise in magnetism and MOKE-related techniques, creating a highly synergistic partnership. These joint efforts have already resulted in several high-impact publications and successful multi-instrumental experiments, demonstrating the strong complementarity between the expertise and experimental capabilities of the collaborating laboratories.

SOLARIS National Synchrotron Radiation Centre

The AGH team is actively involved in the operation and scientific development of the PEEM and XAS beamlines at SOLARIS National Synchrotron Radiation Centre. This collaboration is intensive and long-term in nature, involving many jointly conducted beamtimes and continuous experimental campaigns. It is further demonstrated by a significant number of published results, reflecting the strong scientific output of this sustained cooperation.