Recent demonstrations of magnetotransport effects in antiferromagnets (AFMs) make them  attractive candidates for usage as active elements in future spintronic devices [1]. 
We investigated the magnetic properties of antiferromagnetic NiO(001) thin films in epitaxially grown (Fe)/NiO/MgO(dMgO)/Cr/MgO(001) system for different thicknesses of MgO, dMgO. Figure 1 shows exemplary room temperature x-ray absorption spectra acquired with linear polarization of the photon beam, recorded at the Ni2+ L2 edge in the NiO/MgO(18 Å)/Cr. The results of systematic XMLD measurements show that with increasing dMgO, the rotation of NiO spins from in plane towards out of plane direction occurs. The analysis of the XMLD results together with the analysis of low-energy electron diffraction (LEED) pattern, brought us to the conclusion that for NiO layer grown on a wedge-shaped MgO underlayer, the magnetic anisotropy in NiO can be modulated by exerting appropriate strain from its bottom interface. 
While strain allows tuning magnetic anisotropy of the AFM from its bottom interface, interaction with the ferromagnetic cover layer enables to influence the magnetic state of the AFM from its top interface. The interfacial exchange coupling between Fe and NiO spins in Fe/NiO/MgO(dMgO)/Cr/MgO(001) was directly confirmed by XMLD- and XMCD- Photoemission Electron Microscope (PEEM) measurements (Fig. 2). The competition between exchange coupling to the ferromagnet and the strain-induced anisotropy creates a multiple domain structure in the NiO thin film. 

1. Jungfleisch, M. B., Zhang, W. & Hoffmann, A. Perspectives of antiferromagnetic spintronics. Phys. Lett. A 382, 865–871 (2018).

Figure 1. Exemplary Ni2+ L2-edge x-ray absorption spectra at γ = 0° (black line) and γ = 60° (red line) obtained at room temperature for NiO/MgO(18.3 Å)/Cr/MgO(001). The scheme in the inset shows the geometry of the XMLD experiment. (Source: Sci. Rep. 13, 4824 (2023))

Figure 2. (a, c) The Fe L3 XMCD-PEEM images obtained for Fe/NiO/MgO(10 Å)/Cr and Fe/NiO/ MgO(200 Å)/Cr, respectively. (b) and (d) corresponding Ni L2 XMLD-PEEM images acquired with vertical polarization. (e) and (f) a schematical illustration of spin structure with directions of magnetic moments indicated by the arrows for Fe/NiO/MgO(10 Å)/Cr and Fe/NiO/MgO(200 Å)/Cr, respectively. (Source: Sci. Rep. 13, 4824 (2023)).

Written by: Weronika Janus

The publication can be found here:
W. Janus et al., Tunable Magnetic Anisotropy of Antiferromagnetic NiO in (Fe)/NiO/MgO/Cr/MgO(001) Epitaxial Multilayers, Sci Rep 13, 4824 (2023). doi:10.1038/s41598-023-31930-z

A group of researchers representing leading scientific centers from Poland, Germany, and the USA is conducting joint research on innovative solutions in the field of energy storage and conversion. The team includes specialists from, among others, the Faculty of Energy and Fuels at AGH University of Science and Technology in Kraków, Warsaw University of Technology, the Mineral and Energy Economy Research Institute of the Polish Academy of Sciences, the University of Münster, and Lawrence Berkeley National Laboratory. 

 Fig.1. Figure: XAS results for TM L-edges demonstrating the presence of reduced species on the surface of LMR materials as a function of electrolyte composition (a–d). Comparison of the performance of lithium batteries with LMR electrodes, both with and without protective surface layers (f-h).

Their work focuses on advanced materials and technologies for next-generation batteries, which could play a crucial role in the energy transition and the development of a sustainable economy. In their latest study, the authors investigate lithium- and manganese-rich layered oxide materials (LMR), considered among the most promising cathodes for lithium-ion and lithium-metal batteries. This is due to their high specific capacity, resulting not only from conventional transition metal redox reactions (cationic redox) but also from additional oxygen anion redox reactions (anionic redox) occurring in these materials. Unfortunately, anionic redox leads to capacity and voltage fading and triggers the formation of reconstructed surface layers. While much attention has been paid to the impact of bulk oxygen redox on surface structure, less is known about how surface reconstruction layers affect oxygen redox reactions and overall electrochemical performance. In this context, X-ray absorption spectroscopy (XAS) played a crucial role in elucidating the mechanisms at play, enabling detailed tracking of the oxidation states of transition metals and oxygen in both bulk and surface regions. XAS studies revealed that, during cycling, low-potential Mn/Co redox couples mainly appear at particle surfaces, which enhance charge storage but simultaneously promote transition metal dissolution. XAS also confirmed that rapid capacity fading in LMR || Li cells is associated with the formation of resistive layers on the lithium anode surface, causing increased cell resistance and kinetic degradation, even as the cathode maintains high activity. The stability of the LMR surface—engineered through electrolyte additives—proved to be a critical parameter, allowing stabilization of both oxygen and low-potential transition metal redox processes and significantly improving battery lifespan. These findings, made possible by XAS investigations, deepen our understanding of surface–bulk interactions and the impact of reconstructed layers on material properties, guiding future optimization of advanced battery systems.

The publication can be found here:

In our studies we investigated the influence of the proximity of the antiferromagnetic CoO layer on the magnetic properties of ultrathin wüstite (FeO) films. Comparative Mössbauer spectroscopy measurements for MgO/FeO/MgO(001) and MgO/FeO/CoO/MgO(001) show that the neighboring CoO layer can significantly enhance the ordering temperature (T_N) of wüstite. The T_N of CoO in the FeO/CoO bilayer was determined with a use of X-ray magnetic linear dichroism  (XMLD) measurements.

Antiferromagnets (AFMs) due to their unique properties are promising candidates for the next generation spintronic materials [1], [2]. A wide group of AFM materials seems to be useless for applications due to the low ordering temperature, above which the long-range antiferromagnetic order vanishes. The limitation of low T_N can be overcome using the magnetic proximity effect [3]. In our study we proved that the proximity of CoO strongly influences the magnetic properties of the FeO layer. For the FeO layers grown on 2 nm-thick CoO, the ordering temperature of FeO was increased by 100 K due to the magnetic proximity. This result shows that the limitation of the low ordering temperature of wüstite can be overcome by the antiferromagnetic proximity. To determine the T_N of CoO in the FeO/CoO bilayer, we performed X-ray magnetic linear dichroism (XMLD) measurements. X-ray absorption spectra (XAS) were collected at the PIRX beamline of the National Synchrotron Radiation Centre SOLARIS. Figure 1 shows exemplary normalized XAS spectra for a CoO thickness of 2 nm in FeO/CoO, collected under normal and 60^o X-ray incidence angles at 80 K. Systematic studies of CoO XAS spectra as a function of temperature enabled us to determine the T_N of CoO in FeO/CoO bilayer.

Fig. 1.  Co L₃ edge XAS spectra at φ = 0° (black solid line) and φ = 60° (red dashed line) obtained for FeO/CoO at 80 K. Inset shows the measurement geometry. (source: Appl. Phys. Lett. 120, 072404 (2022))

[1] V. Baltz, A. Manchon, M. Tsoi, T. Moriyama, T. Ono, and Y. Tserkovnyak, Antiferromagnetic Spintronics, Rev Mod Phys 90, 15005 (2018).
[2] P. K. Manna and S. M. Yusuf, Two Interface Effects: Exchange Bias and Magnetic Proximity, Phys Rep 535, 61 (2014).
[3] D. Hou, Z. Qiu, and E. Saitoh, Spin Transport in Antiferromagnetic Insulators: Progress and Challenges, NPG Asia Mater 11, 35 (2019).

The publication can be found here:

A. Kozioł-Rachwał et al., Beating the Limitation of the Néel Temperature of FeO with Antiferromagnetic Proximity in FeO/CoO, Appl Phys Lett 120, 072404 (2022).

Virgin and Yb-implanted epitaxial ZnO films were investigated by XANES. This study revealed a strong polarization dependence of films determined by the orientation of the polarization vector of the synchrotron radiation to the sample surface. It also indicated that the implantation and subsequent annealing have an important influence on the native point defect complexes in the ZnO. The analysis of the obtained data suggests that the donor-acceptor complexes are present both in as grown and implanted films and may influence their electrical properties. This suggestion was confirmed by previous Hall measurements showing that the resistivity of annealed ZnO:Yb film with a fluence of 5e15 ions/cm² decreases by about one order compared to the one with a fluence of 5e14 ions/cm².

Usage of ZnO doped by Yb, in optical and optoelectronic applications is not possible without better understanding of how presence of defects and/or their agglomerates alters the electronic structure, and chemical and physical properties of these materials. In this work, we studied virgin and Yb-implanted epitaxial ZnO films employing X-ray absorption technique (such as polarization- dependent XANES) available at the PIRX (former PEEM/XAS) beamline at National Synchrotron Radiation Centre SOLARIS. Analysis of experimental spectra (together with theoretical simulations, confirmed the presence of donor-acceptor complexes (mVZn - nVO, m = 1,4; n = 1,2) in the samples under study, see Figure 1. It was also concluded that oxidation state of Yb in ZnO is 3+, and that Yb are surrounded by oxygen in pseudo octahedra. This is consistent with the XPS findings and previously conducted RPES investigations. Different doses of implantation disturb the orientation of these octahedra with respect to the growth of direction of film that was observed from an inversion of the polarization dependence for samples with different Yb fluences. Ultimately, our study aims to deepen understanding of implantation-induced defects, their interaction with host matrix defects, and efforts to eliminate, manipulate and/or reorganize these defects via annealing to achieve good quality material useful for optoelectronic applications.

Figure 1. (c) Comparison of O K-edge XANES spectra of a reference ZnO film and of ZnO:Yb films with different doses of Yb (5e14 and 5e15 atoms/cm²). All samples are after a Rapid Thermal Annealing. (d) O K-edge XANES spectra obtained by linear combination of selected theoretical models calculated by FEFF code for different polarization geometry.

The publication can be found here:

Y. Syryanyy, M. Zajac, E. Guziewicz, W. Wozniak, Y. Melikhov, M. Chernyshova, R. Ratajczak, and I. N. Demchenko, Polarized Dependence of Soft X-Ray Absorption near Edge Structure of ZnO Films Implanted by Yb, Mater Sci Semicond Process 144, 106609 (2022). 

In a world that needs to transition to environmentally friendly energy sources, green hydrogen is emerging as a key player. The term 'green' is symbolically assigned to hydrogen, meaning that this type of power generation is the most ecological and free of pollutants. Green hydrogen can be produced through the electrolysis or photolysis of water. It seems that using a photoelectrochemical cell to produce hydrogen using direct solar energy is the best solution. Bilayer and multilayered systems based on CuO, especially in combination with TiO₂ seem to be the most frequently studied of all heterostructured nanomaterials when considering green hydrogen generation. This work describes the various architectures of TiO₂/CuO bilayers obtained through sequential reactive magnetron sputtering. Synchrotron measurements were carried out at SOLARIS centre and allowed to draw conclusions concerning the oxidation state of copper and the electronic structure of the bilayer thin films for green hydrogen generation.

The first author of the publication, Dr. Eng. Joanna Banaś-Gac, explains the main idea behind the conducted experiment: 

TiO₂(top)/CuO bilayer was created as a result of covering rough bottom layer of CuO with smooth top surface of TiO₂ (Fig.1c). Inverse configuration, CuO(top)/TiO₂, was a heterojunction originated as rough bottom layer coated with rough top surface (Fig.1d). Finding the correlation between the structural and optical properties, surface morphology, and photoelectrochemical performance of bilayers with diverse configurations allowed to identify the conditions which provide more efficient photoelectrochemical reactions in the case of TiO₂(top)/CuO over inverse configuration. One of the characterization techniques corresponding to the electronic structure was X-ray absorption spectroscopy (XAS) in the surface sensitive mode, i.e., Total Electron Yield TEY (PIRX beamline). Based on the analysis performed, it could be stated that the interface created between the rough surface of CuO and the smooth TiO₂ surface ensures the highest photocurrent when the top layer is of about 150 nm. For the CuO/TiO₂ heterojunction with a rough/rough interface, the photoelectrochemical performance improves with an increasing top layer thickness up to 100 nm. The photocurrent exhibits a cathodic character for both the TiO₂(top)/CuO and the CuO(top)/TiO₂ bilayers.

Fig. 1 Cross-section HR-TEM images of TiO₂(top)/CuO a) and CuO(top)/TiO₂ b) thin film bilayers  together with schemes of interfaces formed by rough/smooth c) and rough/rough d) surfaces and also proposed mechanism of photoelectrodes performance e) and f).

Link to the publication:
Joanna Banaś-Gac, Marta Radecka, Eduard Llobet , Ewa Partyka-Jankowska, Katarzyna Zakrzewska, Different architectures of thin film bilayers based on TiO₂ and CuO for green hydrogen generation, International Journal of Hydrogen Energy, Volume 136, 10 June 2025, Pages 1073-1085, doi: 10.1016/j.ijhydene.2025.03.036.