CA23136

Magnetism and chirality: twisting spins, light, and lattices for faster-than-ever spintronics

Principal investigator

THz Excitation of Circularly Polarized Raman-Active Phonons in LaAlO₃

In collaboration with the THz free electron laser facility TELBE at the Helmholtz Zentrum Dresden-Rossendorf and ETH Zürich, researcher Fabian Graf conducted a short-term scientific mission, supervised by Steven L. Johnson and Martina Basini.

The mission focused on participating in a beamtime experiment aimed at the THz pumping and detection of circularly polarized Raman-active phonons in LaAlO₃.


Experiment Highlights

  • A circularly polarized THz electric field was used to excite specific Raman-active phonon modes.
  • The experiment was designed to investigate ultrafast lattice dynamics and the potential for light-driven control of phonon states in complex oxides.

A schematic of the circularly polarized THz field used in the experiment is shown in the figure.

Towards Spin Wave Spectroscopy in Altermagnets and Antiferromagnets

This research project aims to advance the understanding and experimental exploration of spin wave phenomena in altermagnets and antiferromagnets. By leveraging cutting-edge spectroscopy techniques, we seek to investigate spin dynamics and magnon-phonon interactions in novel magnetic materials.

Collaboration

This project is a joint effort between:

  • Institute of Physics, Czech Academy of Sciences
    Supervisor: Helena Reichlová

  • University of Konstanz
    Supervisor: Sebastian Goennenwein

 
  • Research Highlights

     

    • Development and Optimization of a Spin Wave Spectroscopy Setup
      A new experimental setup for spin wave spectroscopy has been successfully implemented and optimized at the University of Konstanz, enabling high-precision measurements of spin dynamics.

    • Magnon-Phonon Coupling in YIG
      Experimental measurements of magnon-phonon coupling in yttrium iron garnet (YIG) have been conducted, focusing on the interaction mechanisms affecting propagating spin waves.

Power dissipation in altermagnetic MnTe-based Hall device

This project consists in implementing a power dissipation experiment to the study of an altermagnetic MnTe-based Hall cross. Through this work, we aimed at bringing confirmation to theoretical predictions regarding the dissipation of currents generated by Hall effects, while also investigating new ways of characterizing altermagnetic materials.

This project is a colloration between Laboratoire des Solides Irradiés, Ecole Polytechnique (Valentin Desbuis) and Institute of Physics, Czech Academy of Sciences (Dominik Kriegner).

A schematic of the electrical configuration : A load charge is connected on the transverse contact to investigate the dissipation occuring in the system.

Phonon Generation through Magnetoelastic Coupling

In collaboration with the gruop Nanoscaled Magnonic Hybrids at Rheinland-Pfälzische Technische Universität (RPTU) in Kaiserslautern, we investigated the generation of acoustic phonons via magnetoelastic coupling by applying a radio frequency (RF) field to patterned magnetic structures. Using Brillouin Light Scattering (BLS) spectroscopy, the interaction between the magnetization dynamics and the substrate’s elastic modes is analyzed to explore energy transfer mechanisms.

 

Research Highlights

Beyond demonstrating a proof of concept for magnetoelastic phonon generation, the study identifies critical factors influencing the efficiency of this process, including the relevant excitation frequency range, the external magnetic field conditions, and the geometric characteristics of the excitation structures. These insights lay the groundwork for future development of hybrid platforms that integrate phononic and spintronic functionalities for advanced signal processing applications.
 
In the photo, a Brillouin Light Scattering (BLS) setup. Taken from https://pirro.physik.rptu.de

Exploring Magnetic Topological Insulators Through Advanced Spectroscopy Techniques

This Short-Term Scientific Mission (STSM) focuses on unraveling the structural and electronic properties of magnetically doped and intrinsically nonmagnetic ternary van der Waals (vdW) compounds.

Collaboration

This project is a joint effort between:

  • University of Calabria, Italy
    Supervisor: Prof. Marco Papagno
  • Baku State University, Azerbaijan
    Supervisor: Prof. Ziya Aliev
  •  

Research Highlights

Surface and Electronic Structure Analysis

The mission began with spectroscopic investigation of doped and undoped vdW materials. X-ray Photoelectron Spectroscopy (XPS) was used to identify chemical environments and oxidation states, while Angle-Resolved Photoemission Spectroscopy (ARPES) provided insights into changes in electronic band structure.
 
Impact of Magnetic Dopants
The study focused on how magnetic doping induces structural distortions and influences topological surface states, including potential gap openings, an essential feature in realizing magnetic topological phases.
 
Scientific Impact
The findings support ongoing research into quantum materials with potential applications in spintronics, topological quantum computing, and energy conversion. The mission also strengthens international collaboration in the field of vdW-based topological materials, paving the way for joint future studies.

Exploring Non-Linear Transport in ScFe₄Al₈ for Spintronic Applications

This research project is part of the exploration of non-centrosymmetric materials for spintronics. The compound ScFe₄Al₈, recently identified as a promising candidate, has structural and magnetic properties that could generate non-linear transport effects. The aim is to assess its potential for future electronic devices exploiting broken symmetry.

Collaboration

  • Institute of Physics, Czech Academy of Sciences
    Supervisors: Helena Reichlová, Daniel Scheffler
  • IFW of Dresden (measurements campaign)
  •  

Research Highlights

Analysis of the current–voltage curves obtained on samples with a thin film of ScFe₄Al₈ reveals weak but detectable non-linear contributions for intermediate experimental conditions of temperature and applied magnetic field. These signatures, extracted using the delta method, translate into variations in slope depending on the magnetic field. Although still to be confirmed, these results constitute an initial indication consistent with the expected behaviour for non-centrosymmetric materials.

Transverse IV curves at 200 K on ScFe₄Al₈ thin film showing subtle non-linear behavior with slope variations under different magnetic fields.

Uranium based altermagnet candidates: UNiGa and UCr2Si2C

As part of the search for altermagnetic materials, two uranium based materials are selected: UNiGa and UCr2Si2C. This STSM focused on synthesizing phase pure UNiGa and UCr2Si2C samples and single crystals of UCr2Si2C that is large enough for single crystal physical property measurements.

Collaboration

This project is a joint effort between:

  • MPI for Chemical Physics of Solids

Supervisor: Dr. Eteri Svanidze

  • Koç University
    Supervisor: Assoc. Prof. Umut Aydemir

Research Highlights

    • Synthesis of UCr2Si2C

Arc melting is successfully performed to obtain UCr2Si2C without the need for 30 day annealing process.

    • Single crystal UCr2Si2C

A single crystal of size 1400 um x 170 um is separated from the arc melted button. Composition of single crystal is confirmed by EDX analysis as UCr2Si2C, which can be used for various measurements such as resistivity, Hall effect, heat capacity, and strain.

Ultrafast phononic control of spins in van der Waals multiferroic CuCrP2S6

Supported by the COST program, the investigation of the research teams led by Dr. Wenjing Yan at the University of Nottingham and Dr Alexey V. Scherbakov at Technique Universität Dortmund explored a new area of research: the interaction between magnons and phonons in a 2D van der Waals (2D-vdW) multiferroic materials. In addition to multiferroicity, such materials present distinct advantages since their electronic, optical, and symmetry characteristics can be further engineered through  “Lego-type” stacking of atomic layers.

Research Highlights:

During this short-term mission of Dr. Yan to TU Dortmund, the researchers performed magneto-optical pump-probe  experiments on hybrid phononic nanostructures based on multiferroic CuCrP2S6  (CCPS) compound, which were specifically engineered to excite different phonon modes. Results from temperature- and magnetic-field-dependent measurements indicated desirable magnon-phonon coupling in CCPS. These insights suggest promising avenues for future research on the coherent phononic control of magnetism in 2D systems.

Spin-Lattice Coupling in Ti-Doped GdMnO3 Single Crystals

In collaboration with the Institute of Physics of Advanced Materials, Nanotechnology and Photonics (IFIMUP), University of Porto, researcher Muhammad Faisal Ashraf conducted a Short-Term Scientific Mission (STSM) under the framework of COST Action CA23136 (CHIROMAG), supervised by Prof. Agostinho Moreira. The mission focused on investigating spin-lattice interactions in Ti-doped GdMnO3 single crystals using temperature-dependent Raman spectroscopy. The aim was to investigate how magnetic order affects lattice vibrations and how chemical substitution modifies spin-lattice coupling in multiferroic manganites.

Research Highlights:

During this STSM, Raman spectra were recorded from 10 K to 300 K, tracking the symmetrical stretching phonon mode near magnetic transition regions. The deviation of the phonon wavenumber from the thermal expansion fit (dashed curve) is associated with spin-lattice coupling dominated by ferromagnetic interactions and is stronger in the Ti-doped sample than in the undoped crystal, even though the Néel temperature (TN) decreases because Ti is non-magnetic. These observations provide direct experimental evidence of spin-phonon coupling and offer new insight into how lattice vibrations interact with magnetic order in multiferroic complex oxides.

Temperature dependence of the symmetrical stretching phonon mode, showing deviation from thermal expansion behavior.

Skyrmions in 3D Nanostructures

During a Short-Term Scientific Mission (STSM) within COST Action CHIROMAG (CA23136), Dr. Alberto Anadón Barcelona carried out a research stay at TU Wien, hosted by Amalio Fernández-Pacheco.

The mission focused on the fabrication and magneto-optical characterization of perpendicularly magnetized multilayers integrated onto 3D nanostructures. Multilayer stacks were optimized using magnetron sputtering and conformally deposited onto 3D FEBID nano-scaffolds previously fabricated at INMA-CSIC.

Research Highlights:

  • Growth of PMA multilayers on 3D scaffolds
    Successful deposition of multilayers with strong perpendicular magnetic anisotropy onto non-planar FEBID structures, ensuring uniform coating and structural integrity.
  • Optical access to 3D magnetic textures
    Magneto-optical Kerr effect (MOKE) and dark-field MOKE measurements revealed clear magnetic domain signatures on the curved 3D structures, demonstrating their suitability for optical probing.

Imaging of chiral magnetic states formed on curvilinear surfaces

Takeaki Gokita conducted a Short-Term Scientific Mission (STSM) within the framework of COST Action CHIROMAG (CA23136) at the Max Planck Institute for Chemical Physics of Solids, hosted by Dr. Claire Donnelly.

 

This STSM focused on imaging magnetic states deposited on curved surfaces using magnetic force microscopy (MFM) and nitrogen-vacancy magnetometry to investigate how curvature influences magnetic properties.

 

Research Highlights:

Observation of circular magnetic objects on curved surfaces

We observed circular magnetic objects in [Pt/Co] multilayers formed on curved surfaces using MFM. The local magnetic fields generated by the MFM tip may contribute to the stabilization of these circular magnetic objects.

 

Fe(II) Chiral Spin Switches based on 1,3,4-Thiadiazole ligands

This project is a collaboration between

Institute of Physics, Czech Academy of Science, Czech Republic

Dr. Sriram Sundaresan

and

Johannes Gutenberg University, Mainz, Germany

Supervisor: Prof. Dr. Eva Rentschler

Research Highlight:

A chirality-dependent magnetic response was identified in a family of Fe(II) thiadiazole spin crossover complexes investigated during the STSM. While spin crossover compounds typically switch between low-spin and high-spin states in response to temperature or other external stimuli the present system shows a remarkable dependence on the chiral composition of the molecular material. The enantiopure complexes undergo a complete thermal spin crossover, displaying a transition temperature (T₁/₂) of approximately 195 K. In contrast, the racemic form remains stabilised in the high-spin state over the same temperature range and does not exhibit a thermal spin transition. This clear difference between enantiopure and racemic forms highlights the important influence of chirality and crystal packing on the magnetic behaviour of spin crossover systems. The accompanying χMT measurements (Figure below) further show chirality-dependent magnetic response.

Wedge-Optimised Co/Cu/Co Multilayers for Interface-Driven Spintronics (Pt vs. Bi₂Te₃)

This Short-Term Scientific Mission (STSM), carried out within COST Action CA23136 (CHIROMAG), was conducted as a collaboration between the University of Messina (Italy) and Bolu Abant İzzet Baysal University (Turkey), hosted by Dr. Carmelo Corsaro and Dr. Enza Fazio, and led by Dr. Mustafa Erkovan.

 

Research Highlight:

A reliable and reproducible growth protocol for Co/Cu multilayers was established using combined profilometry, XPS, and XRR calibration, enabling precise thickness and interface control and providing a solid baseline for SAF-oriented studies.

A wedge-based variation of the Cu spacer thickness was used to explore the interlayer exchange coupling regime and define the SAF-relevant parameter space for subsequent interface-driven spintronic studies.

 

Confocal magnetron sputtering system used for the deposition of Co/Cu multilayers during the STSM at the University of Messina.

Chiroptical Detection of in-wire Built Polymer Junction by Raman Spectroscopy

Through the Short-Term Scientific Mission) STSM support program of CHIROMAG (CA23136) Cost Action Dr. Ramazan Kizil conducted the following research in collaboration with the research team of the host Dr. Agostinho Moreira at University of Porto, Porto Portugal.

The Participating Institutes:

Istanbul Technical University, Chemical Engineering Department,

Nanostructured Electronic Devices Lab

 Supervisor Dr. Ramazan Kizil

Institute of Physics of Advanced Materials, Nanotechnology and Photonics (IFIMUP), University of Porto

Supervisor Dr. Agostinho Moreira

 

Research Highlights:

Synthesis and Characterization of Chiral Molecular Layer Junction In Metallic Nanowires

A Chiral molecule of (S)-2-Aminobutane-1,4-dithiol was polymerized on electrodeposited metal surfaces (Ag or Ni) inside a membrane and covered by Ni electroplating in Istanbul Technical University. The chirality conferred nanowires were characterized using FEG-SEM (Figure 1). 

Raman Spectroscopic Characterization and Circular Polarization-Resolved Raman Optical Activity

The chemical composition of the chiral molecular layer incorporated in nanowires were meticulously investigated using Raman spectroscopy. First, 633 nm Red laser excitation was used to collect fluorescence-free Raman spectra (inset image) of the nanoscopic Chiral entity in the wire. After carefully elucidating the chemical structure of the chiral junction, circularly polarized Green laser was used to detect chiroptical response from the junction. Raman optical activity was observed in several Raman modes due to the chiral carbon atom (Figure 2)

Figure 1. SEM micrographs of polymer nanojunctions of molecule (S)-2-Aminobutane-1,4-dithiol monomer within nanowires, making Ag-Polymer-Ni and Ni-Polymer-Ni junctions to be used as Chiral spin valve or tunnel junction devices. These nanowires were grown in Istanbul and Raman analyses were made in Porto.
Figure 2. Raman spectra of the Chiral Molecular Junction obtained by red laser line excitation (inset) and chiroptical enhancements Raman modes due to to the chiral atom.

Relativistic Dynamics of Topologically Unprotected Antiferromagnetic Domain Walls

In collaboration with with Dr. Unai Atxitia from CSIC, Dr. Rubén M. Otxoa from Hitachi- Cambridge Laboratory Lab. conducted a Short-Term Scientific Mission (STSM) under the framework of COST Action CA23136 (CHIROMAG).

The mission of this STSM was to develop a theoretical description on how spin–orbit-torque induces effective fields to control soliton motion and to explore regimes where the topological charge becomes field-dependent. Beyond fundamental understanding, the stay aimed to translate

these insights into a new schemes for nanoscale control, sensing, and unconventional information processing.


Research Highlights:
In this work, we demonstrate that for topologically unprotected 90° domain walls, we derive a closed relativistic velocity law and a Lorentz-like width contraction where the topological charge becomes kinematically adaptive rather than conserved. This breakdown of topological

conservation is not merely a curiosity: it produces strongly enhanced mobilities, enabling velocities up to six times higher than topologically protected walls under the same driving conditions. Atomistic simulations confirm the theory without fitting parameters, yielding clear,

experimentally testable predictions and revealing a deeper link between soliton kinematics, relativistic contraction, and symmetry constraints.

 

 

Figure: (a) Schematics of a domain wall (DW) under spin-orbit field, where the field aligns with the spins at the left edge ϕL and when it is perpendicular to the central spin of the DW. (b) Continuous reduction of the angular span between edges defining the topological charge, Q for both field orientations. (c) Edge angles ϕL,R(u) versus HSO/HSO c. Symbols: atomistic simulations for both geometries. (d) Topological charge Q/Q0 versus HSO/HSO c.

Spin-Wave Dynamics in Canted Antiferromagnets with Intersublattice DMI

During a Short-Term Scientific Mission (STSM) at Politecnico di Bari, supervised by Prof. Riccardo Tomassello, we developed a theoretical model to describe how spin waves behave in a two-sublattice antiferromagnet when intersublattice Dzyaloshinskii–Moriya interaction (DMI) is present.

Research Highlights:

We found that this type of DMI has a strong effect on the system. It increases the frequency of the higher spin-wave mode and changes the other from a circular motion to a elliptical one.

Our model based on two macrospins explains the evolution of these two modes under an external magnetic field, with validity confirmed by numerical simulations . These results demonstrate that chiral interactions can control spin dynamics, opening new avenues for utilizing interlayer DMI in tunable spintronic terahertz devices.

Spin-Lattice Coupling in Yttrium-doped GdMnO3 Multiferroic Single Crystals

STSM Grantee: Muhammad Faisal Ashraf
Host Institution: IFIMUP – University of Porto
Supervisor: Prof. Agostinho Moreira

In collaboration with the Institute of Physics of Advanced Materials, Nanotechnology and Photonics (IFIMUP), University of Porto, researcher Muhammad Faisal Ashraf conducted a Short-Term Scientific Mission (STSM) under the framework of COST Action CA23136 (CHIROMAG), supervised by Prof. Agostinho Moreira, with support in Raman spectroscopy measurements from Dr. Rui Vilarinho Silva. The mission focused on investigating spin-lattice interactions in Y-doped GdMnO3 single crystals using temperature-dependent Raman spectroscopy. The aim was to investigate how magnetic order affects lattice vibrations and how chemical substitution modifies spin-lattice coupling in multiferroic manganites.

 

Research Highlights

During this STSM, Raman spectra were recorded from 10 K to 300 K, tracking the symmetrical stretching phonon mode near the magnetic transition region. The phonon wavenumber shows a clear downshift relative to the expected anharmonic thermal expansion behavior (dashed curve) indicating dominant ferromagnetic (FM) interactions, while an upshift would correspond to antiferromagnetic (AFM) interactions. Compared with pure GdMnO3, the characteristic minimum near 20 K becomes suppressed in the Y-doped samples, suggesting modification of the magnetic exchange interactions by Y substitution. The observed deviation also indicates that FM correlations develop already above the Néel temperature (TN ≈ 40 K), providing clear evidence of spin-lattice coupling in the system.

Temperature dependence of the symmetrical stretching phonon mode, showing deviation from thermal expansion behavior.

Optimization of ultra-thin films for spin-orbit torque enabled sensing elements

This STSM explores the integration of thin films of BiTe/Ta and SbTe/Ta and ultrathin CoFeB/MgO grown in different laboratories. This project is a collaboration between the Faculty of Sciences of the University of Porto (Portugal, Dr. João Pedro Araújo) and the Eindhoven University of Technology (Netherlands, Dr. Diana Leitao), and led by Francisco Moutinho.


Research Highlights:
Established an experimental protocol for the integration of thin film growth combining ion milling, deposition, and annealing. Milling rate was calibrated using the profilometer, and magnetic characterization was performed via MOKE.

Sputtering systems used at a) FCUP and b) TU/e
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