Magnetic van der Waals materials have mainly been investigated in their bulk form or as few-layer flakes. Because of the challenges in producing atomically thin films, only a few have been isolated as monolayers, which typically exhibit long-range magnetic order below 150 K. In this Letter, we use molecular beam epitaxy to synthesize Co-doped Fe_{5}GeTe_{2}, achieving precise control over both thickness and composition. We demonstrate ferromagnetism well above room temperature in multilayer samples and present clear evidence of ferromagnetic ordering in monolayers up to ∼200  K. The changes in Curie temperature and magnetic anisotropy as a function of composition exhibit similar trends in both monolayers and thicker films, indicating that the magnetic properties are primarily governed by intralayer magnetic interactions. Through element-specific x-ray magnetic circular dichroism and density-functional theory, we identify the substitution site of Co dopants and reveal the mechanism behind the Curie temperature enhancement induced by Co doping. Our findings suggest that, despite their weak magnetic moment, Co dopants strengthen the magnetic moments on neighboring Fe atoms and enhance the intralayer ferromagnetic exchange interactions.

Tailoring at will polar textures in ferroelectrics is critical for the development of nanoscale electronics and functional oxide technologies. Freestanding ferroelectric membranes have enabled studies of strain-induced polarization responses, but the control over membrane shape and local polarization typically remains limited to spontaneous buckling or uniaxial mechanical deformations. In this work, we employ a versatile photosensitive-polymer patterning approach to impose programmable bending strain profiles in ferroelectric membranes. Using BaTiO3 as a model system, we demonstrate deterministic 90° polarization rotation driven by engineered in-plane strain, and 180° polarization reversal arising from flexoelectric coupling through a controlled strain gradient. These results establish this programmable bending as a powerful approach to investigate strain-dependent domain structures, leverage flexoelectric effects, and engineer custom ferroelectric landscapes across a wide range of oxide membranes.

The transparent conductor SrVO3 was shown to be insulating in its amorphous state, which is a serious limitation for its potential application in devices being sensible to the high temperature...

The kagome lattice stands as a rich platform for hosting a wide array of correlated quantum phenomena, ranging from charge density waves and superconductivity to electron nematicity and loop current states. Direct detection of loop currents in kagome systems has remained a formidable challenge due to their intricate spatial arrangements and the weak magnetic field signatures they produce. This has left their existence and underlying mechanisms a topic of intense debate. In this work, we uncover a hallmark reconcilable with loop currents: spin handedness-selective signals that surpass conventional dichroic, spin, and spin-dichroic responses. We observe this phenomenon in the kagome metal CsTi_3Bi_5 and we call it the anomalous spin-optical helical effect. This effect arises from the coupling of light' s helicity with spin-orbital electron correlations, providing a groundbreaking method to visualize loop currents in quantum materials. Our discovery not only enriches the debate surrounding loop currents but also paves the way for new strategies to exploit the electronic phases of quantum materials via light-matter interaction.

Two-dimensional transition metal dichalcogenide (TMD) interfaces offer a versatile platform for studying quantum phenomena and developing device functionalities. When distinct TMD monolayers are stacked vertically or laterally stitched, their interfaces can exhibit unique electronic band alignments, giving rise to long-lived interlayer excitons, charge transfer effects, and moiré superlattices with correlated states. Here, we demonstrate that the interface between a large variety of two different epitaxially grown TMD monolayers controls the intensity and sign of the Rashba spin splitting, which is probed using THz spintronic emission. Optimized TMD heterobilayers, such as HfSe2/PtSe2, show enhanced THz emission that surpasses the spin-to-charge conversion efficiency of bulk TMDs, confirming the presence of Rashba states with large spin splitting at the interface. By combining spin- and angle-resolved photoemission spectroscopy with density functional theory, we reveal that the electronic hybridization between the two different TMD monolayers gives rise to extended in-gap states with strong Rashba spin-orbit coupling. The choice of TMD layers enables to engineer the sign and strength of spin-to-charge conversion in van der Waals heterobilayers, enabling to build efficient and tunable THz spintronic emitters.

Magnetic van der Waals materials have mainly been investigated in their bulk form or as few-layers flakes. Due to the challenges in producing atomically thin films, only a few have been isolated as monolayers, which typically exhibit long-range magnetic order below 150 K. In this work, we use molecular beam epitaxy to synthesize Co-doped Fe5GeTe2, achieving precise control over both thickness and composition. We demonstrate ferromagnetism well above room temperature in multilayer samples and present clear evidence of ferromagnetic ordering in monolayers up to ∼200 K. The changes in Curie temperature and magnetic anisotropy with composition exhibit similar trends in both monolayers and thicker films, indicating that the magnetic properties are primarily governed by intralayer magnetic interactions. Through element-specific X-ray magnetic circular dichroism and density functional theory, we identify the substitution site of Co dopants and reveal the mechanism behind the Curie temperature enhancement induced by Co doping. Our findings suggest that, despite their weak magnetic moment, Co dopants strengthen the magnetic moments on neighboring Fe atoms and enhance the intralayer ferromagnetic exchange interactions.

The development of freestanding oxide thin films enables the design of unconventional heterostructures with enhanced functionalities. Here, we explore the fabrication of membranes consisting of dense arrays of ultrathin CoxNi1-x nanowires embedded in a dielectric matrix. We present a lift-off process to create and transfer these membranes while preserving the structural and chemical integrity of the nanopillars. The large axial deformation of the metallic nanostructures is maintained, and their magnetic properties remain largely unaltered after substrate removal. This robustness enables the integration of such strain-engineered, vertically aligned nanocomposites into flexible spintronic and magnetic memory platforms.

Development of self-supporting oxide membrane fabrication using a sacrificial layer method has attracted great attention over the past decade, specifically for their promising integration as devices on silicon and flexible substrates due to their large panel of properties such as ferroelectricity, ferromagnetism, superconductivity, and metal/insulator transition. Known sacrificial layer materials with a perovskite-related structure, such as LaxSr1-xMnO3 and YBa2Cu3O7, are dissolved in acidic or basic solutions. To prevent oxide membranes from being attacked by the sacrificial layer dissolution solution, it is important to find perovskite water-soluble sacrificial buffers. In this work, we evidence the perovskite molybdates AMoO3 (A = Ca, Sr, Ba) as a new ambient-stable and efficient water-soluble sacrificial layer family for the fabrication of oxide membranes. We first show the stability in an ambient environment of CaMoO3, SrMoO3, and BaMoO3 epitaxial films deposited on (001)SrTiO3 substrates and their water dissolution kinetics with membrane release times longer than the SrVO3 material and the well-known Sr3Al2O6 sacrificial layer material. We analyze the etching kinetics via operando optical monitoring of the remaining sacrificial layer surface still attached to the initial template substrate. We found for the molybdate family a first-order reaction kinetics with a main exponential decay, with constants, respectively, of around 11 h, 14 h, and 19 h for CaMoO3, SrMoO3, and BaMoO3. We use this molybdate family to release an 80 nm-thick SrTiO3 membrane on a polydimethylsiloxane support with a smooth morphology observed by atomic force microscopy and a monocrystalline quality observed by high-resolution X-ray diffraction. These results open a range of pseudocubic lattice parameters of the ambient-stable and water-soluble sacrificial buffers with pseudocubic lattice parameters from 3.90 to 4.04 Å for self-supporting perovskite oxide monocrystalline membrane fabrication.

Low-field anisotropic magnetoresistance (AMR) sensors based on epitaxial La1-xSrxMnO3 (LSMO) thin films combine ultra-low noise, good interplay between sensitivity and detectivity, and straightforward fabrication, offering a compelling alternative to giant and tunnel magnetoresistance technologies. Here, by tuning Sr doping (x = 0.15-0.45) of LSMO films grown epitaxially on 4 degrees miscut (001)-oriented SrTiO3 substrates, we achieve fine control of performance parameters tailored to match biomedical environments operating at tightly regulated temperatures. We resort to shape-induced uniaxial magnetic anisotropy and Wheatstone bridge structures to suppress noise and isolate the AMR signal. Temperature-dependent characterization reveals that devices with x = 0.35 deliver optimal sensitivity and lowest electronic noise at 310 K (human body temperature), highlighting their strong potential for biomedical sensing applications.

Systems with pronounced spin anisotropy are pivotal in advancing magnetization switching and spin-wave generation mechanisms that are fundamental to spintronic technologies. Quasi-van der Waals ferromagnets like Cr1+δTe2 represent seminal materials in this field, renowned for their delicate balance between frustrated layered geometries and magnetism. Despite extensive investigation, the nature of their magnetic ground state and the mechanism of spin reorientation under external fields and varying temperatures remain contested. Here, we exploit complementary techniques to reveal a previously overlooked magnetic phase in Cr1+δTe2 (δ = 0.25 - 0.50), which we term orthogonal-ferromagnetism. This phase consists of atomically sharp single layers of in-plane and out-of-plane maximally canted ferromagnetic blocks, which differs from the stacking of multiple heterostructural elements required for crossed magnetism. Contrary to earlier reports of gradual spin reorientation in CrTe2-based systems, we present evidence for abrupt spin-flop-like transitions. This discovery further highlights Cr1+δTe2 compounds as promising candidates for spintronic and orbitronic applications, opening new pathways for device engineering.

In the growing field of low-cost electronics, the epitaxy of complex oxide thin films on a Si substrate requires significant technical means. Therefore, a large attention is paid to the release of a freestanding oxide of interest from its deposition support which is then placed onto a low-cost substrate, via the etching of an intermediate sacrificial layer. The use of a sacrificial layer offers several advantages since the flexible polymer exploited for the transfer can also be fully utilized to design a flexible heterostructure. For green technology, more and more research investigations are being undertaken on these sacrificial layers etched by water. While Sr3Al2O6 and SrVO3 are archetypical examples, the need to find new materials with different lattice parameters and symmetry is critical to reach the epitaxy of numerous materials of interest. In this study, the possibilities of an A-site cationic variation in AVO3 with A = Sr and/or Ca thin films are highlighted to expand the water-soluble material's family reaching the smallest lattice parameter ever presented up to now. In addition to bring various compounds with different ageing properties to the literature, optical spectrophotometry operando characterizations to follow the chemical etching of the sacrificial layers in real-time are exploited.

Low-field anisotropic magnetoresistance (AMR) sensors based on epitaxial La 1− x Sr x MnO 3 (LSMO) thin films combine ultra-low noise, good interplay between sensitivity and detectivity, and straightforward fabrication, offering a compelling alternative to giant and tunnel magnetoresistance technologies. Here, by tuning Sr doping ( x = 0.15–0.45) of LSMO films grown epitaxially on 4° miscut (001)-oriented SrTiO 3 substrates, we achieve fine control of performance parameters tailored to match biomedical environments operating at tightly regulated temperatures. We resort to shape-induced uniaxial magnetic anisotropy and Wheatstone bridge structures to suppress noise and isolate the AMR signal. Temperature-dependent characterization reveals that devices with x = 0.35 deliver optimal sensitivity and lowest electronic noise at 310 K (human body temperature), highlighting their strong potential for biomedical sensing applications.

The diversity of 2D materials and their van der Waals (vdW) stacking presents fertile ground for engineering novel multifunctional materials and quantum states of matter. This permits unique opportunities to tailor the electronic properties of vdW heterostructures by the insertion of only a single 2D material layer. However, such vdW materials engineering at the atomic scale has yet to be investigated for spin-charge interconversion phenomena. Here, we report on the control of these effects at the monolayer level, where a drastic increase in intensity and change in sign of THz spintronic emission are demonstrated by inserting a single layer of MoSe2 between PtSe2 and graphene in a fully epitaxial, large area stacked structure. By using a combination of spin and angle resolved photoemission and density functional theory to reveal the electronic and spin structures, we illustrate two different mechanisms relying on charge transfer and electronic hybridization for the formation of Rashba states, which are responsible for spin-charge conversion and hence the THz spintronic emission. These findings open new pathways to design, at the atomic scale, efficient THz spintronic emitters made of 2D materials and other spintronic devices based on spin-charge interconversion phenomena.

In the growing field of spintronic devices incorporating antiferromagnetic materials, control of the domain configuration and Néel axis orientation is critical for technological implementations. Here we show by X-ray magnetic linear dichroism in photoelectron emission microscopy how antiferromagnetic properties of LaFeO3 (LFO) thin films can be tailored through epitaxial strain. LFO films were grown via molecular beam epitaxy with precise stoichiometric control, using substrates that span a range of strain states—from compressive to tensile—and crystal symmetries, including different crystallographic orientations. First, we show that epitaxial strain dictates the Néel axis orientation, shifting it from completely in-plane under compressive strain to completely out-of-plane under tensile strain, regardless of the substrate crystal symmetry. Second, we find that LFO films grown on cubic substrates exhibit a fourfold distribution of antiferromagnetic domains, but can be controlled by varying the substrate miscut, while those on orthorhombic substrates, regardless of strain state, form large-scale monodomains, a highly desirable feature for spintronic applications. Precise control over antiferromagnetic domain configurations and Néel axis orientation is essential for technological advancement of spintronic devices. Here, the authors use epitaxial strain to tailor the magnetic properties of LaFeO3 thin films, demonstrating a crystal engineering approach which may have much wider applicability.

van der Waals ferromagnets, such as Fe5GeTe2, offer a promising platform for spintronic devices based on chiral magnetic textures, provided a significant Dzyaloshinskii-Moriya interaction (DMI) can be induced to stabilize the textures. Here, we directly measure DMI in epitaxial Fe5GeTe2 thin films using Brillouin light scattering spectroscopy and observe a consistent DMI (D = 0.04 mJ/m2) across various thicknesses. Its weak thickness dependence, combined with the nominally symmetric film interfaces, suggests a bulk origin. Although we do not determine the microscopic mechanism, our findings are compatible with ab initio calculations linking DMI to partial ordering of Fe split sites. Additionally, we find a low magnetic dissipation (α < 0.02). The observed DMI, which could be further enhanced by optimizing the Fe site ordering, combined with low dissipation, makes Fe5GeTe2 a strong candidate for exploring the dynamics of chiral magnetic textures in two-dimensional materials.

This study highlights the structural, chemical, and magnetic properties of Fe 3 O 4 /MgCr 2 O 4 /Fe 3 O 4 spinel oxide trilayers and the conditions for preserving the attributes of Fe 3 O 4 thin films for potential device applications.

The integration of perovskite oxides onto flexible substrates has witnessed significant advancements owing to the development of an epitaxial lift-off technique utilizing a Sr3Al2O6 sacrificial layer. However, Sr3Al2O6 is susceptible to instability in both air and high-temperature oxygen atmospheres, potentially leading to degradation during the growth of the functional oxide layer. In this study, we investigate the use of an oxygen-deficient La0.7Sr0.3MnO3 as capping layer, and demonstrate its ability to stabilize Sr3Al2O6 films in ambient air. We successfully synthesized freestanding La0.7Sr0.3MnO3 membranes by etching this sacrificial layer and transferring them onto flexible polymer substrates. Importantly, the magnetic properties of the La0.7Sr0.3MnO3 films are preserved in these membranes. Our results underline that employing a thin manganite capping layer ensures both high structural quality and the preservation of functional properties in the resulting membranes.

Altermagnetism defies conventional classifications of collinear magnetic phases, standing apart from ferromagnetism and antiferromagnetism with its unique combination of spin-dependent symmetries, net-zero magnetization, and anomalous Hall transport. Although altermagnetic states have been realized experimentally, their integration into functional devices has been hindered by the structural rigidity and poor tunability of existing materials. First, through cobalt intercalation of the superconducting 2H-NbSe_2 polymorph, we induce and stabilize a robust altermagnetic phase and using both theory and experiment, we directly observe the lifting of Kramers degeneracy. Additionally, we present spectroscopic insight into a previously hinted low-temperature phase, and provide evidence of its electronic origin. While shedding light on overlooked aspects of altermagnetism, these findings open pathways to spin-based technologies and lay a foundation for advancing the emerging field of altertronics.

Van der Waals materials provide a versatile toolbox for the emergence of new quantum phenomena and the fabrication of functional heterostructures. Among them, the trihalide VI3 stands out for its unique magnetic and structural landscape. Here we investigate the spin and orbital magnetic degrees of freedom in the layered ferromagnet VI3 by means of temperature-dependent x-ray absorption spectroscopy and x-ray magnetic circular and linear dichroism. We detect localized electronic states and reduced magnetic dimensionality, due to electronic correlations. We furthermore provide experimental evidence of (a) an unquenched orbital magnetic moment (up to 0.66(7)) in the ferromagnetic state, and (b) an instability of the orbital moment in proximity of the spin reorientation transition. Our results support a coherent picture where electronic correlations give rise to a strong magnetic anisotropy and a large orbital moment, and establish VI3 as a prime candidate for the study of orbital quantum effects.

Abstract We explore how strain impacts the band structure of metallic-phase VO2 thin films deposited on TiO2(101) substrates. Employing a combination of X-ray absorption linear dichroism and valence band measurements, we demonstrate that strain can alter the intrinsic band structure anisotropy of metallic VO2. Our findings reveal that reducing the thickness of VO2 films leads to a more isotropic band structure. This observation is further supported by an analysis of the electronic population redistribution in the $${d}_{{||}}{-}{\pi }^{* }$$ d || − π * bands, which affects the screening length and induces effective mass renormalization. Overall, our results underscore the potential of strain manipulation in tailoring the electronic structure uniformity of thin films, thereby expanding the scope for engineering VO2 functionalities.