Elzbieta Gradauskaite

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Gradauskaite

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Elzbieta

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0000-0001-9607-1855

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Publications 1 - 10 of 13

Magnetoelectric Phase Control at Domain-Wall-Like Epitaxial Oxide Multilayers
Gradauskaite, Elzbieta; Yang, Chia-Jung; Efe, Ipek; et al. (2025)
Advanced Functional Materials
Ferroelectric domain walls are nanoscale objects that can be created, positioned, and erased on demand. They often embody functional properties that are distinct from the surrounding bulk material. Enhanced conductivity, for instance, is observed at charged ferroelectric domain walls. Regrettably, domain walls of this type are scarce because of the energetically unfavorable electrostatics. This hinders the current technological development of domain-wall nanoelectronics. Here this constraint is overcome by creating robust domain-wall-like objects in epitaxial oxide heterostructures. Charged head-to-head (HH) and tail-to-tail (TT) junctions are designed with two ferroelectric layers (BaTiO3 and BiFeO3) that have opposing out-of-plane polarization. To test domain-wall-like functionalities, an ultrathin ferromagnetic La0.7Sr0.3MnO3 layer is inserted into the junctions. The interfacial electron or hole accumulation at the interfaces, set by the HH and TT polarization configurations, respectively, controls the LSMO conductivity and magnetization. Thus it is proposed that trilayers reminiscent of artificial domain walls provide magnetoelectric functionality and may constitute an important building block in the design of oxide-based electronic devices.
Ferroelectric Thin Films for Oxide Electronics
Müller, Marvin; Efe, Ipek; Sarott, Martin F.; et al. (2023)
ACS Applied Electronic Materials
Ferroelectric materials have set in motion numerous ultralow-energy-consuming device concepts that can be integrated into state-of-the-art complementary metal–oxide–semiconductor technology. Their nonvolatile, spontaneous electric polarization makes them promising candidates to control functionalities at the nanoscale with energy-efficient electric fields only. In this spotlight article, we start with a brief introduction to ferroelectric materials, the challenges involving the design of thin films and review the state-of-the-art of their integration into various electronic applications. Revolutionary in situ and operando diagnostic tools allowing the monitoring of the technology-relevant polarization state during the material design, or its operation will be detailed. Concepts such as chiral states in ferroelectrics and neuromorphic-type switching will be addressed to provide a comprehensive view on the evolution of ferroelectric states for the next generation of low-energy-consuming electronics. Finally, we discuss the most recent developments in the field, including the emergence of ferroelectricity at the nanoscale and in two-dimensional systems.
Defeating depolarizing fields with artificial flux closure in ultrathin ferroelectrics
Gradauskaite, Elzbieta; Meier, Quintin N.; Gray, Natascha; et al. (2023)
Nature Materials
Material surfaces encompass structural and chemical discontinuities that often lead to the loss of the property of interest in so-called dead layers. It is particularly problematic in nanoscale oxide electronics, where the integration of strongly correlated materials into devices is obstructed by the thickness threshold required for the emergence of their functionality. Here we report the stabilization of ultrathin out-of-plane ferroelectricity in oxide heterostructures through the design of an artificial flux-closure architecture. Inserting an in-plane-polarized ferroelectric epitaxial buffer provides the continuity of polarization at the interface; despite its insulating nature, we observe the emergence of polarization in our out-of-plane-polarized model of ferroelectric BaTiO₃ from the very first unit cell. In BiFeO₃, the flux-closure approach stabilizes a 251° domain wall. Its unusual chirality is probably associated with the ferroelectric analogue to the Dzyaloshinskii–Moriya interaction. We, thus, see that in an adaptively engineered geometry, the depolarizing-field-screening properties of an insulator can even surpass those of a metal and be a source of functionality. This could be a useful insight on the road towards the next generation of oxide electronics.
Interfacial control of ferroic order in oxide heterostructures
Gradauskaite, Elzbieta (2022)
Oxide electronics have emerged as an alternative to replace the current silicon-based technology. Owing to a rich elemental composition compared to that of doped silicon, transition metal oxides can host a wide range of physical phenomena. This is especially true when oxides are integrated into ultrathin epitaxial heterostructures, in which additional properties arise from the created interfaces. Their crystal structure is, furthermore, compatible with long-range order. In particular, ferromagnetic and ferroelectric systems have gathered considerable attention due to their characteristic non-volatile response to applied external fields. While ferroic oxides are indisputable candidates for low-energy-consuming applications, there are still a few setbacks left to overcome in order to integrate them into competitive device schemes. With the work performed during the course of this thesis, we strive to provide solutions for existing limitations to the implementation of ferroic states in nanoscale devices. We place emphasis on interfacial effects in epitaxial heterostructures and their influence on ferroic order. Making use of a non-conventional approach of epitaxially combining layers with different ferroic anisotropies, we uncover novel fundamental concepts likely to benefit the ever-evolving field of oxide electronics. We identify the in-plane-polarized Aurivillius compounds as promising candidates for tuning interfacial electrostatics and achieving interfacial polar continuity in epitaxial hybrid heterostructures with ferroelectric perovskite oxides. The stabilized coalescent layer-by-layer growth mode ensures the single-crystallinity of these layered ferroelectrics, while the sub-unit-cell thickness control of the films enables detailed investigations of their polar state. For instance, the thickness-dependent in-plane-polarized domain configuration in the resulting epitaxial Aurivillius films prompts us to propose new means for ferroic domain and functional domain-wall engineering via structural defect ordering. Moving ahead with the integration of Aurivillius films into perovskite-based heterostructures, we show that the Aurivillius compounds utilized as in-plane-polarized buffer layers can overcome the notorious limitation associated with the critical thickness for ferroelectricity in canonical out-of-plane-polarized perovskite ferroelectrics. We additionally demonstrate that buffers of the Aurivillius phase can be instrumental for domain and domain-wall engineering in the room-temperature multiferroic BiFeO3. In particular, we observe a uniform chirality stabilized in Néel-like domain walls in BiFeO3 grown on our in-plane-polarized Bi5FeTi3O15 Aurivillius layer. This likely constitutes one of the first experimental signatures of the electric counterpart to the Dzyaloshinskii-Moriya interaction in magnetically ordered compounds. Lastly, we explore magnetoelectric phase control in heterostructures combining both ferroelectric and ferromagnetic order. In a proof-of-concept multiferroic heterostructure, we mimic magnetoelectric domain walls by inserting ultrathin ferromagnetic La1-xSrxMnO3 in between two ferroelectric layers. We show that its magnetization and conductivity can be controlled by changing polarization directions in the adjacent ferroelectric layers only. This opens up new possibilities for voltage-based tuning of magnetization and conductivity at the nanoscale.
Current-driven dynamics and ratchet effect of skyrmion bubbles in a ferrimagnetic insulator
Vélez, Saül; Ruiz-Gómez, Sandra; Schaab, Jakob; et al. (2022)
Nature Nanotechnology
Magnetic skyrmions are compact chiral spin textures that exhibit a rich variety of topological phenomena and hold potential for the development of high-density memory devices and novel computing schemes driven by spin currents. Here, we demonstrate the room-temperature interfacial stabilization and current-driven control of skyrmion bubbles in the ferrimagnetic insulator Tm3Fe5O12 coupled to Pt, showing the current-induced motion of individual skyrmion bubbles. The ferrimagnetic order of the crystal together with the interplay of spin–orbit torques and pinning determine the skyrmion dynamics in Tm3Fe5O12 and result in a strong skyrmion Hall effect characterized by a negative deflection angle and hopping motion. Further, we show that the velocity and depinning threshold of the skyrmion bubbles can be modified by exchange coupling Tm3Fe5O12 to an in-plane magnetized Y3Fe5O12 layer, which distorts the spin texture of the skyrmions and leads to directional-dependent rectification of their dynamics. This effect, which is equivalent to a magnetic ratchet, is exploited to control the skyrmion flow in a racetrack-like device.
Nanoscale Design of High-Quality Epitaxial Aurivillius Thin Films
Gradauskaite, Elzbieta; Gray, Natascha; Campanini, Marco; et al. (2021)
Chemistry of Materials
Efforts for the integration of ferroelectric materials in nonvolatile, low energy consuming memories have so far been focused on perovskite oxide materials. Their down-scaling for nanodevices is, however, hindered by finite-size effects, and alternative materials offering more robust polar properties are required. Layered ferroelectrics of the Aurivillius phase have since emerged as promising candidates with robust polarization at subunit-cell thicknesses. Their controlled growth in the epitaxial thin film form has unfortunately remained elusive. Here, we demonstrate the stabilization of the coalescent layer-by-layer growth mode of the Bin+1Fen−3Ti3O3n+3 (BFTO) Aurivillius family homologues. We define the growth conditions for high-quality, single-crystalline thin films exhibiting ferroelectricity from the first half-unit-cell. We demonstrate the process to be effective for several homologous Aurivillius compositions, which highlights its general applicability. Our work thus provides the systematic framework for the integration of high-quality epitaxial layered ferroelectrics into oxide electronics.
Magnetoelectric domain engineering from micrometer to Ångstrøm scales
Giraldo Castaño, Leidy Marcela; Simonov, Arkadiy; Sim, Hasung; et al. (2024)
Physical Review Research
The functionality of magnetoelectric multiferroics depends on the formation, size, and coupling of their magnetic and electric domains. Knowing the parameters guiding these criteria is a key effort in the emerging field of magnetoelectric domain engineering. Here we show, using a combination of piezoresponse-force microscopy, nonlinear optics, and x-ray scattering, that the correlation length setting the size of the ferroelectric domains in the multiferroic hexagonal manganites can be engineered from the micron range down to a few unit cells under the substitution of Mn3+ ions with Al3+ ions. The magnetoelectric coupling mechanism between the antiferromagnetic Mn3+ order and the distortive-ferroelectric order remains intact even at substantial replacement of Mn3+ by Al3+. Hence, chemical substitution proves to be an effective tool for domain-size engineering in one of the most studied classes of multiferroics.
Multiferroic heterostructures for spintronics
Gradauskaite, Elzbieta; Meisenheimer, Peter Benjamin; Müller, Marvin; et al. (2021)
Multiferroics: Fundamentals and Applications
For next-generation technology, magnetic systems are of interest due to the natural ability to store information and, through spin transport, propagate this information for logic functions. Controlling the magnetization state through currents has proven energy inefficient. Multiferroic thin-film heterostructures, combining ferroelectric and ferromagnetic orders, hold promise for energy efficient electronics. The electric field control of magnetic order is expected to reduce energy dissipation by 2-3 orders of magnitude relative to the current state-of-the-art. The coupling between electrical and magnetic orders in multiferroic and magnetoelectric thin-film heterostructures relies on interfacial coupling though magnetic exchange or mechanical strain and the correlation between domains in adjacent functional ferroic layers. We review the recent developments in electrical control of magnetism through artificial magnetoelectric heterostructures, domain imprint, emergent physics and device paradigms for magnetoelectric logic, neuromorphic devices, and hybrid magnetoelectric/spin-current-based applications. Finally, we conclude with a discussion of experiments that probe the crucial dynamics of the magnetoelectric switching and optical tuning of ferroelectric states towards all-optical control of magnetoelectric switching events.
In-situ monitoring of epitaxial ferroelectric thin-film growth
Sarott, Martin F.; Gradauskaite, Elzbieta; Nordlander, Johanna; et al. (2021)
Journal of Physics: Condensed Matter
In ferroelectric thin films, the polarization state and the domain configuration define the macroscopic ferroelectric properties such as the switching dynamics. Engineering of the ferroelectric domain configuration during synthesis is in permanent evolution and can be achieved by a range of approaches, extending from epitaxial strain tuning over electrostatic environment control to the influence of interface atomic termination. Exotic polar states are now designed in the technologically relevant ultrathin regime. The promise of energy-efficient devices based on ultrathin ferroelectric films depends on the ability to create, probe, and manipulate polar states in ever more complex epitaxial architectures. Because most ferroelectric oxides exhibit ferroelectricity during the epitaxial deposition process, the direct access to the polarization emergence and its evolution during the growth process, beyond the realm of existing structuralin situdiagnostic tools, is becoming of paramount importance. We review the recent progress in the field of monitoring polar states with an emphasis on the non-invasive probes allowing investigations of polarization during the thin film growth of ferroelectric oxides. A particular importance is given to optical second harmonic generationin situ. The ability to determine the net polarization and domain configuration of ultrathin films and multilayers during the growth of multilayers brings new insights towards a better understanding of the physics of ultrathin ferroelectrics and further control of ferroelectric-based heterostructures for devices.
Ferroelectric Domain Engineering Using Structural Defect Ordering
Gradauskaite, Elzbieta; Hunnestad, Kasper A.; Meier, Quintin N.; et al. (2022)
Chemistry of Materials

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Elzbieta Gradauskaite

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