On-line SPICE-SPIN+X Seminars

On-line Seminar: 21.01.2026 - 15:00 CET

Orbital-to-spin conversion in magnetic heterostructures

Pietro Gambardella, Department of Materials, ETH Zurich, Switzerland

Spin-orbital torques are central to spintronics, enabling current-induced magnetization switching, excitation of spin waves, and manipulation of noncollinear spin textures in nanoscale devices [1]. Besides the electron’s spin, recent investigations have pointed out the importance of the orbital degree of freedom in generating and transferring angular momentum from charge currents to spin systems. The generation and transport mechanisms of nonequilibrium orbital momenta are currently heavily debated. This talk will discuss the related issue of orbital-to-spin conversion, which is relevant for orbital transport, torques, and pumping phenomena. Experimental examples will include nonmagnetic/ferromagnetic bilayers [2,3], ferrimagnetic alloys [4] and garnets [5], and antiferromagnets [6].

References:

[1] Current-induced spin-orbit torques in ferromagnetic and antiferromagnetic systems, A. Manchon, J. Železný, I.M. Miron, T. Jungwirth, J. Sinova, A. Thiaville, K. Garello, and P. Gambardella, Rev. Mod. Phys. 91, 035004 (2019).

[2] Giant orbital Hall effect and orbital-to-spin conversion in 3d, 5d, and 4f metallic heterostructures, G. Sala and P. Gambardella, Phys. Rev. Res. 4, 033037 (2022).

[3] Mitigation of Gilbert damping in the CoFe/CuOx orbital torque system, S. Ding, H. Wang, W. Legrand, P. Noël, and P. Gambardella, Nano Lett. 24, 10251 (2024).

[4] Orbital Torque in Rare-Earth Transition-Metal Ferrimagnets, S. Ding, M.-G. Kang, W. Legrand, and P. Gambardella, Phys. Rev. Lett. 132, 236702 (2024).

[5] Orbital pumping in ferrimagnetic insulators, H.Wang, M.-G. Kang, D. Petrosyan, S. Ding, R. Schlitz, L.J. Riddiford, W. Legrand, and P. Gambardella, Phys. Rev. Lett. 134, 126701 (2025).

[6] Generation, transmission, and conversion of orbital torque by an antiferromagnetic insulator, S. Ding, P. Noël, G. K. Krishnaswamy, N. Davitti, G. Sala, M. Fantauzzi, A. Rossi, P. Gambardella, Nat. Comm. 16, 9239 (2025).

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On-line SPICE-SPIN+X Seminars

On-line Seminar: 28.01.2026 - 15:00 CET

Orbital ordering-induced unconventional magnetism

Johannes Knolle, TU Munich

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, we show that altermagnetism can also form as an interaction-induced electronic instability in a lattice without the crystallographic sublattice anisotropy. We discuss different microscopic examples of orbital-induced altermagnetism and promising experimental directions.

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On-line SPICE-SPIN+X Seminars

On-line Seminar: 03.06.2026 - 15:00 CET

TBA

Jörn Venderbos, Drexel

TBA

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On-line SPICE-SPIN+X Seminars

On-line Seminar: 15.07.2026 - 15:00 CET

TBA

Daniel F Agterberg, UW

TBA

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On-line SPICE-SPIN+X Seminars

On-line Seminar: 06.05.2026 - 15:00 CET

TBA

Marcel Franz, UBC

TBA

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On-line SPICE-SPIN+X Seminars

On-line Seminar: 08.04.2026 - 15:00 CET

Altermagnetism: an unconventional quantum state of matter

Rafael Fernandes, UIUC

Magnetism is the posterchild of how the interplay between electron-electron interactions and quantum physics promotes novel macroscopic phenomena. Historically, the evolution of our understanding of magnetism has been related to the discovery of new paradigms in condensed-matter physics, as exemplified by the connections between antiferromagnetism and Mott insulators, spin glasses and non-ergodic states, and spin liquids and fractionalized excitations. Recently, a new framework proposed to classify magnetic phases brought renewed interest in unconventional magnetic states, which are qualitatively distinct from ferromagnets and standard Néel antiferromagnets. Among those, altermagnetic phases have been met with enthusiasm by the scientific community, as they display properties found in both ferromagnets (like the splitting of electronic bands with opposite spins) and conventional antiferromagnets (like the absence of a net magnetization). Formally, what distinguishes these three different magnetic states are the crystalline symmetries that, when combined with time reversal, leave the system invariant. In the case of altermagnets, because these symmetries involve rotations, the system is endowed with unique properties such as nodal spin-splitting and piezomagnetism. In this talk, I will introduce the concept of altermagnetism and discuss its connection to long-standing problems in the field of quantum materials, such as multipolar magnetism and electronic liquid-crystalline phases. I will also present the predicted experimental signatures of altermagnetic order in thermodynamic and transport properties, and show that altermagnets provide a fertile ground to realize non-trivial topological and superconducting phenomena in quantum materials.

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On-line SPICE-SPIN+X Seminars

On-line Seminar: 14.01.2026 - 15:00 CET

Magnetic excitations beyond the single- and double- magnons

Hebatalla Elnaggar, Helmholtz Center Berlin

Conventional wisdom suggests that one photon that carries one unit of angular momentum (1h) can change the spin angular momentum of a magnetic site with one unit (ΔM = ±1h) at most following the selection rules. This implies that a two-photon process such as 23 resonant inelastic X-ray scattering (RIXS – see Fig. 1a-c) can change the spin angular momentum of a magnetic system with a maximum of two units (ΔM = ± 2h) [1]. Herein we describe a triple-magnon excitation in the altermagnetic system, -Fe2O3, which contradicts this conventional wisdom that only 1- and 2-magnon excitations are possible in a resonant inelastic X-ray scattering experiment [2].

Figure 1: Schematic of Resonant Inelastic X-ray Scattering (RIXS). (a) The initial state of a 3d transition metal plus a photon with energy ℏin, wave-vector kin. (b) The intermediate state where a 2p electron is excited to the empty 3d states leaving a core-hole that exists for few fs. (c) The final state where a valence 3d electron fills the core-hole and a photon with energy ℏout, wave-vector kout is emitted. The energy and momentum transfer are given by ℏ(in - out) and ℏ(kin-kout), respectively. (d) Fe 2p3d RIXS measured in -Fe2O3 single crystal where we observed multi-magnons.

We observe an excitation at exactly three times the magnon energy, along with additional excitations at four and five times the magnon energy, suggesting the presence of quadruple and quintuple magnons as well (see Fig. 1d). Guided by theoretical calculations, we reveal how a two-photon scattering process can create exotic higher-rank magnons and the relevance of these quasiparticles for understanding spin non-conserving interactions where the lattice degree of freedom acts as a reservoir of angular momentum.

References:
[1]- A. Nag, et. al., Many-body physics of single and double spin-flip excitations in NiO, Phys. Rev. Lett., 124, 067202 (2020).
[2]- H. Elnaggar, et. al., Magnetic excitations beyond the single- and double-magnons, Nat. Commun. 14, 2749 (2023).

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On-line SPICE-SPIN+X Seminars

On-line Seminar: 25.02.2025 - 15:00 CET

Emerging Altermagnetism and Polar States in Strained Metallic RuO2 Films

Bharat Jalan, University of Minnesota

Department of Chemical Engineering and Materials Science, University of Minnesota, Twin Cities

RuO2, a rutile 4d-transition metal oxide, exhibits a unique crystal structure with both edge- and corner-sharing octahedra. This intrinsic anisotropy, when combined with strain engineering, provides a powerful avenue for tuning anisotropic electronic and optical properties. However, from a synthesis perspective, challenges such as variable Ru valence states, Ru/O stoichiometry control, anisotropic strain states, and structural defects can make it difficult to distinguish intrinsic properties from extrinsic effects in RuO2 thin films – a classic trick in the pursuit of novel functionalities in quantum materials.

In this talk, I will highlight our group’s efforts in overcoming these synthesis challenges while demonstrating metallicity in epitaxial RuO2 films down to the unit cell scale. Through a combination of advanced X-ray scattering, X-ray absorption spectroscopy, transmission electron microscopy, temperature-dependent transport, magneto-optical measurements, and density functional theory (DFT) calculations, we uncover robust magnetism in epitaxially strained RuO2, consistent with an altermagnetic metallic phase [1-4]. Additionally, we reveal a novel polar phase in strained films with significant implications for electrical transport – an unexpected treat in the realm of functional oxides. I will discuss these findings in detail, emphasizing their sensitivity to material defects and structure – key ingredients that are often overlooked but crucial in determining emergent quantum phenomena.

Reference:

1. S. G. Jeong†, I. H. Choi†, S. Nair, L Buiarelli, B. Pourbahari, J. Y. Oh, N. Bassim, A. Seo, W. S. Choi, R. M. Fernandes, T. Birol, L. Zhao, J. S. Lee, and B. Jalan, Altermagnetic polar metallic phase in ultra-thin epitaxially-strained RuO2 films, (under review) (2025) [arxiv] †Equal contribution
2. S. G. Jeong, I. H. Choi, S. Lee, J. Y. Oh, S. Nair, J. H. Lee, C. Kim, A. Seo, W. S. Choi, T. Low, J. S. Lee, and B. Jalan, Anisotropic Strain Relaxation-Induced Directional Ultrafast Carrier Dynamics in RuO2 Films, Sci. Adv. 11, eadw7125 (2025)
3. S. G. Jeong, S. Lee, B. Lin, Z. Yang, I. H. Choi, J. Y Oh, S. Song, S. W. Lee, S. Nair, R. Choudhary, J. Parikh, S. Park, W. S. Choi, J. S. Lee, J. M. LeBeau, T. Low, and B. Jalan, Metallicity and Anomalous Hall Effect in Epitaxially-Strained, Atomically-thin RuO2 Films, PNAS 122(24) e2500831122
4. S. G. Jeong, B. Y. X. Lin, M. Jin, I. H. Choi, S. Lee, Z. Yang, S. Nair, R. Choudhary, J. Parikh, A. Santhosh, M. Neurock, K. A. Stoerzinger, J. S. Lee, T. Low, Q. Tu, J. M. LeBeau, and B. Jalan, Strain-Stabilized Interfacial Polarization Tunes Work Function Over 1 eV in RuO2/TiO2 Heterostructures, under review (2025) [arxiv]

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On-line SPICE-SPIN+X Seminars

On-line Seminar: 26.11.2025 - 15:00 CET

Novel glimpse into ground states of quantum matter

Vesna Mitrović, Brown University

In this talk I would describe novel in-situ ``interferometry'' technique that is employed to probe ground state properties of the complex materials. Examples of the power of this nuclear magnetic resonance inspired technique will be illustrated on magnetic and frustrated materials.
Specifically, I will show how this technique can be used to sense changes in quantum mechanical ground state wavefunction through a high temperature magnetic phase transition.

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On-line SPICE-SPIN+X Seminars

On-line Seminar: 12.11.2025 - 15:00 CET

Superconducting spintronics with magnetically compensated materials

Jacob Wüsthoff Linder, NTNU

Altermagnets have emerged as intriguing materials supporting strongly spin-polarized
currents despite the lack of a net magnetization. We demonstrate that altermagnets
enable several promising functionalities when merged with conventional superconductors.
We predict that altermagnets act as spin-filters for triplet Cooper pairs
and that they can function as cryogenic spin-valves acting as a memory device without stray fields, offering
high storage densities. Finally, we discuss the interplay between p-wave magnetism
and superconductivity both intrinsically in a material and via the proximity effect in a bilayer.
We show that p-wave magnets induce a charge-to-spin conversion in combination with
superconductors that, unexpectedly, is even larger than in the normal state.

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