News

27.06.2024 New Publication in Antiferromagnetic Spintronics

A publication with Helen Gomonay and Tobias Wagner revealing ultrafast domain wall motion in Mn2⁢Au through permalloy capping has been published in Physical Review B.

Antiferromagnets offer much faster dynamics compared to their ferromagnetic counterparts but their order parameter is extremely difficult to detect and control. So far, controlling the Néel order parameter electrically is limited to only very few materials where Néel spin-orbit torques are allowed by symmetry. In this work, they show that coupling a thin ferromagnet (permalloy) layer on top of an antiferromagnet (Mn2⁢Au) solves a major roadblock—the controlled reading, writing, and manipulation of antiferromagnetic domains. They confirm by atomistic spin dynamics simulations that the domain wall patterns in the Mn2⁢Au are imprinted on the permalloy, therefore allowing for indirect imaging of the Néel order parameter. Their simulations show that the coupled domain wall structures in Mn2⁢Au-Py bilayers can be manipulated by either acting on the Néel order parameter via Néel spin-orbit torques or by acting on the magnetization (the ferromagnetic order parameter) via magnetic fields. In both cases, they predict ultrahigh domain wall speeds on the order of 8.5 km/s. Thus, employing a thin ferromagnetic layer has the potential to easily control the Néel order parameter in antiferromagnets even where Néel spin-orbit torques are forbidden by symmetry. The controlled manipulation of the antiferromagnetic order parameter provides a promising basis for the development of high-density storage and efficient computing technologies working in the THz regime.

You can find the publication under Phys. Rev. B 109, 224431 (2024).

25.06.2024 Upcoming SPICE Young Research Leaders Group Workshop: Magnetism in van der Waals materials: current challenges and future directions

Workshop, July 8th - 10th 2025

Van der Waals materials are a fruitful playground for developing new emergent physical phenomena from bulk down to the two-dimensional limit. Regarding spins, magnetism arises in these systems either naturally —i.e., in van der Waals magnets— or by design —that is, engineering proximity or twist effects in van der Waals heterostructures, even if the starting layers are not magnetic per se!—. Some fundamental properties underlying these magnetic layers are the spin-switching and spin-transport mechanisms, the magneto-elastic coupling or the emergence of topological spin textures (e.g., skyrmions) and topological effects (e.g., the anomalous spin Hall effect), just to mention a few. Understanding these basic properties is key to its integration into devices, impacting in areas like spintronics, magnonics, or opto-electronics.

A characteristic fingerprint of this field is multi-disciplinarity since several disciplines are strongly involved, including chemical growth, advanced physical characterization techniques at the nanoscale (magnetic imaging, magneto-transport measurements, optical characterization, mechanical testing, …), and theoretical modeling, among others. This workshop gathers young researchers working in these areas, offering a holistic vision of the field of magnetism in van der Waals materials, discussing its current challenges, and envisioning future directions.

Overall, we aim to realize new synergetic effects not only between van der Waals layers but, even more importantly, between young researchers, thus creating a forum for future collaborations and scientific exchange.

This workshop is organized by SPICE as part of the Gutenberg International Conference Center (GICC) at Johannes Gutenberg University Mainz (JGU). The GICC is funded through the German Research Foundation’s (DFG) university allowance in the Excellence Strategy program and aims at fostering JGU as a national and international research hub. By organizing regular conferences and workshops in fields of excellent JGU research, the GICC provides a platform to build interest networks and collaborations – to promote exchange and dialog among academics and research groups from all over the world.

25.06.2024 Upcoming SPICE Workshop on Quantum Functionalities of Nanomagnets

Workshop, June 17th - 19th 2025

Although numerous solid-state platforms are being developed for quantum applications significant challenges remain with respect to control and scalability, making the development of new qubit technologies a foundational activity pursued intensely. An under-explored platform – nanomagnets – is rapidly demonstrating unique features that could further invigorate the advancement of quantum technologies. This workshop aims to discuss the quantum aspects of tailored magnetic platforms, whose main advantage lies in the high degree of control in manipulation, preparation, parameter tunability, and all-magnetic device integration. It will also discuss some of the recent demonstrations of quantum operations using magnets, the discovery of materials with direct relevance to quantum technology, and the development of sensors able to detect magnetic signals with quantum sensitivity. The event will present the state-of-the-art and opportunities for synergy between quantum technology and tailored spin structures, which holds exciting promise for the creation and preservation of quantum information by magnetic quantum states.

If you are interested in this SPICE-Workshop, please click the button, to apply before March 3rd, 2025. If your application is successful, you will be contacted in March 2025 with a link to register. The conference fee is 550 euros. Accommodation is not included. The online conference fee (live in Zoom participation) is 50 euros. Poster Sessions and Poster Flash Presentations will be organized only for those attending in person.

25.06.2024 Upcoming SPICE Workshop on Characterization and control of quantum materials with optical vortex beams

Workshop, June 10th - 12th 2025

The fascinating physics of optical vortices, in particular light carrying orbital angular momentum (OAM), has resulted in a large interest and currently OAM light can be generated with high precision in a wide photon energy range. Consequently, also the interplay between optical vortices and matter has been investigated in a broad range of phases, from atoms and molecules to solids and plasmas. For example, the study of optical transitions in semiconductors nicely showed the increased complexity of the allowed optical transitions and how the OAM is transferred to the system. This workshop aims to take this a step further and explore how optical vortices can be used to characterize and control complex quantum materials. Through this workshop, it is foreseen to form and bring together a community and form an overview of current and future research endeavors.

Given the exploratory character, the scope of the workshop is purposely kept broad and topics can include, but are not limited to, the following:
• interaction of vortex beams with quantum condensates
• interaction/coupling of the Berry phase associated with the optical OAM vortex with the topological Berry phase in condensed matter
• inducing quantum phase transitions with OAM
• measuring and driving hidden order with vortex beams
• generation and characterization of chiral bosonic modes

Participants are encouraged to share preliminary (negative) results and conceptual ideas.

If you are interested in this SPICE-Workshop, please click the button, to apply before March 24th, 2025. If your application is successful, you will be contacted in April 2025 with a link to register. The conference fee is 550 euros. Accommodation is not included. The online conference fee (live in Zoom participation) is 50 euros. Poster Sessions and Poster Flash Presentations will be organized only for those attending in person.

25.06.2024 Upcoming SPICE Workshop on Quantum Geometry and Transport of Collective Excitations in (Non-)Magnetic Insulators

Workshop, May 6th - 8th 2025

Quantum geometric properties of band structures and their signatures in experiments have driven condensed matter research over the past decades. This SPICE workshop will focus on recent theoretical and experimental advances in the topological properties of bands formed by magnetic and hybrid bosonic excitations. While the topology of electron bands is well understood, with unambiguous experimental tools to probe theoretical predictions, their bosonic analogs pose challenges. Although bosonic topological excitations, such as magnon Chern bands, Weyl and Dirac semimetals, and nodal-line semimetals have emerged, the lack of quantized responses and the ambiguity of thermal Hall and Nernst effects prevent their distinct experimental identification. Furthermore, traditional spectroscopic methods for resolving bosonic modes, such as inelastic neutron scattering, lack the contrast to resolve topological boundary states. One possible route to bring the topological excitations under control is to make use of highly tunable platforms, such as magnonic crystals and stacked van der Waals layers. Additionally, the ease of hybridization of magnonic excitations with phonons, photons, and plasmons can provide novel opportunities to directly probe the topological fingerprint.

With this workshop, we aim to provide a forum where experts and students can discuss the latest developments, challenges, and future directions in topological magnetism. Some exciting challenges that we aim to address include:

-Identify direct experimental signatures for topological bosonic excitations

-Explore the impact of many-body interactions on the quantum geometry of the single particle spectrum and transport

-Identify the microscopic origins of thermal Hall conductivity in magnetic and non-magnetic insulators

-Engineer the quantum geometry and topology of collective excitations by non-Hermitian, non-equilibrium, and Floquet control

-Explore technological applications of topological boundary modes in spintronics and magnonics

We invite contributions from the fields of magnetism, spin and heat transport, spintronics, and magnonics. In addition, we strongly encourage students to apply, and to present their work in the poster session.

If you are interested in this SPICE-Workshop, please click the button, to apply before March 3rd, 2025. If your application is successful, you will be contacted in March 2025 with a link to register. The conference fee is 550 euros. Accommodation is not included. The online conference fee (live in Zoom participation) is 50 euros. Poster Session will be organized only for those attending in person.

12.06.2024 New Publication in Altermagnetism

A publication with Libor Šmejkal about a tool to check whether a symmetry-compensated collinear magnetic material is antiferro- or altermagnetic has been published in SciPost Phys. Codebases.

Altermagnets (AM) is a recently discovered class of collinear magnets that share some properties (anomalous transport, etc) with ferromagnets, some (zero net magnetization) with antiferromagnets, while also exhibiting unique properties (spin-splitting of electronic bands and resulting spin-splitter current). Since the moment compensation in AM is driven by symmetry, it must be possible to identify them by analyzing the crystal structure directly, without computing the electronic structure. Given the significant potential of AM for spintronics, it is very useful to have a tool for such an analysis. This work presents an open-access code implementing such a direct check.

You can find the publication under SciPost Phys. Codebases 30 (2024) (2024).

12.06.2024 New Publication in Antiferromagnetic Spintronics

A publication with Jairo Sinova and Helen Gomonay about magnetic domain engineering in antiferromagnetic Cu⁢Mn⁢As and Mn2Au has been published in Physical Review Applied.

Antiferromagnetic materials hold potential for use in spintronic devices with fast operation frequencies and field robustness. Despite the rapid progress in proof-of-principle functionality in recent years, there has been a notable lack of understanding of antiferromagnetic domain formation and manipulation, which translates to either incomplete or nonscalable control of the magnetic order. Here, they demonstrate simple and functional ways of influencing the domain structure in Cu⁢Mn⁢As and Mn2Au, two key materials of antiferromagnetic spintronics research, using device patterning and strain engineering. Comparing x-ray microscopy data from two different materials, they reveal the key parameters dictating domain formation in antiferromagnetic devices and show how the nontrivial interaction of magnetostriction, substrate clamping, and edge anisotropy leads to specific equilibrium domain configurations. More specifically, they observe that patterned edges have a significant impact on the magnetic anisotropy and domain structure over long distances and we propose a theoretical model that relates short-range edge anisotropy and long-range magnetoelastic interactions. The principles invoked are of general applicability to the domain formation and engineering in antiferromagnetic thin films at large, which will hopefully pave the way toward realizing truly functional antiferromagnetic devices.

You can find the publication under Phys. Rev. Applied 21, 064030 (2024).

11.06.2024 New Publication in Altermagnetism

A publication with Jairo Sinova, Libor Šmejkal, Anna Hellenes and Rafael González Hernández about the observation of a spontaneous anomalous Hall response in the Mn5Si3 d-wave altermagnet candidate has been published in Nature Communications.

Phases with spontaneous time-reversal symmetry (T) breaking are sought after for their anomalous physical properties, low-dissipation electronic and spin responses, and information-technology applications. Recently predicted altermagnetic phase features an unconventional and attractive combination of a strong T-symmetry breaking in the electronic structure and a zero or only weak-relativistic magnetization. In this work, they experimentally observe the anomalous Hall effect, a prominent representative of the T $T$ -symmetry breaking responses, in the absence of an external magnetic field in epitaxial thin-film Mn₅Si₃ with a vanishingly small net magnetic moment. By symmetry analysis and first-principles calculations they demonstrate that the unconventional d-wave altermagnetic phase is consistent with the experimental structural and magnetic characterization of the Mn₅Si₃epilayers, and that the theoretical anomalous Hall conductivity generated by the phase is sizable, in agreement with experiment. An analogy with unconventional d-wave superconductivity suggests that our identification of a candidate of unconventional d-wave altermagnetism points towards a new chapter of research and applications of magnetic phases.

You can find the publication under Nat Commun 15, 4961 (2024).

03.06.2024 New Publication in Altermagnetism

A publication with Libor Šmejkal about the spontaneous formation of altermagnetism from orbital ordering has been published in Physical Review Letters.

Altermagnetism has emerged as a third type of collinear magnetism. In contrast to standard ferromagnets and antiferromagnets, altermagnets exhibit extra even-parity wave spin order parameters resulting in a spin splitting of electronic bands in momentum space. In real space, sublattices of opposite spin polarization are anisotropic and related by rotational symmetry. In the hitherto identified altermagnetic candidate materials, the anisotropies arise from the local crystallographic symmetry. Here, they show that altermagnetism can also form as an interaction-induced electronic instability in a lattice without the crystallographic sublattice anisotropy. They provide a microscopic example of a two-orbital model showing that the coexistence of staggered antiferromagnetic and orbital order can realize robust altermagnetism. They quantify the spin-splitter conductivity as a key experimental observable and discuss material candidates for the interaction-induced realization of altermagnetism.

You can find the publication under Phys. Rev. Lett. 132, 236701 (2024).

31.05.2024 Elasto-Q-Mat was approved for the next funding period

We are proud to announce that the CRC/TRR Elasto-Q-Mat was approved for the second funding period. Elasto-Q-Mat is a collaboration of the universities in Frankfurt, Karlsruhe and Mainz and had great scientific success in the topic of new physical phenomena emerging from a particularly strong coupling between a material's elasticity and its electronic quantum phases within the last four years. The DFG will fund our work for four more upcoming years.

We thank all the members of the CRC for their hard work and dedication to this interesting research field.

You can find the press statement from the DFG here.