α-MnTe is a prototypical altermagnet exhibiting a strong anomalous Hall effect (AHE), despite having a nearly vanishing magnetization. Lately, sample-to-sample variations of the amplitude of the AHE have raised concerns of a possible defect related origin, especially in thin films. Here, we study the AHE in α-MnTe films grown on SrF2 that have the crystal structure and m'm'm magnetic point group symmetry expected for bulk. By studying the scaling of the AHE with conductivity for those films and previously reported measurements in the literature, we find that sample-to-sample variations are well explained by a scaling law consistent with a hopping origin. Importantly, a comparison with other magnetic semiconductors reveals the colossal amplitude of the AHE of α-MnTe compared to its measured spontaneous magnetization from magnetometry and polarized neutron reflectivity. Our findings address the important fundamental question of the origin of the AHE of α-MnTe and further demonstrate the potential of altermagnets as promising spintronic materials.

A long spin‐lifetime of electrons is the holy grail of spintronics, a field exploiting the electron angular momentum as an information carrier and storage unit. Previous reports indicated a spin lifetime, τ s near 10 ns at best in graphene‐based devices at low temperatures. The observation of τ s approaching the ultralong 1,000 ns at room temperature in natural graphite crystals is detailed using magnetic resonance spectroscopy. The relaxation time shows a giant anisotropy: the lifetime of spins, polarized perpendicular to the graphite plane, is more than 50 times longer than for the in‐plane polarization. The temperature dependence of τ s proves that diffusion of spins to the crystallite edges, where relaxation occurs, limits the lifetime. This suggests that graphite is an excellent candidate for spintronic applications, seamlessly integrating with emerging 2D van der Waals technologies.

Time-resolved photoconductivity is widely used to characterize non-equilibrium charge-carrier lifetime, impurity content, and solar cell efficiency in a broad range of semiconductors. Most measurements are limited to the detection of reflection of electromagnetic radiation at a single frequency and a single photoexciting light wavelength. We present a time-resolved photoconductivity instrument that enables broadband frequency detection (essentially from DC to 100 GHz), temperature-dependent measurements, and multiple excitation photon energy. The measurement is realized with the help of a coplanar waveguide, which acts as an efficient antenna and whose performance was tested over 10 MHz-10 GHz. The instrument enables the study of surface and bulk charge-recombination specific processes.

Plastic waste, one of the most critical problems for humankind, poses severe threats to ecosystems, wildlife, and human health. Tracing, quantifying, and identifying types of plastic waste are crucial to understanding its environmental pathways and developing targeted strategies for reduction, recycling, and remediation. To contribute to addressing this global issue, we investigated the spin-labeling capabilities of chlorine dioxide (ClO2) radicals introduced into poly(ethylene terephthalate) and utilized electron spin resonance spectroscopy for detection. The technique is capable of identifying plastic species, as the unpaired electron of the radical molecule is strongly sensitive to its local environment through its coupling parameters. Temperature-dependent measurements revealed that the molecules are immobilized at low temperatures and exhibit well-resolved anisotropic and hyperfine spectra that are quantitatively described by a model spin Hamiltonian. Even above the melting point of water, certain degrees of freedom remain restricted as a result of the polymer matrix. Furthermore, employing a time-series measurement at room temperature enabled us to determine the diffusion coefficient of the molecule in the polymer

The kagome lattice, with its inherent geometric frustration, provides a rich platform for exploring intriguing magnetic phenomena and topological electronic structures. In reduced-symmetry structures, such as twisted kagome systems involving rare earth elements, additional anisotropy can arise, enabling intriguing properties including spin-ice states, magnetocaloric effects, noncollinear magnetic ordering, and the anomalous Hall effect. Here, we report the synthesis of single crystals of ErPdPb, which features a twisted kagome lattice net of Er atoms within the hexagonal ZrNiAl-type structure, and we investigate its magnetic, electronic, and thermal properties. The material exhibits a highly anisotropic, correlated magnetic state below 2.7 K, as evidenced by magnetic, transport, and heat capacity measurements. Density functional theory (DFT) calculations indicate strong easyaxis anisotropy, consistent with experiment and crystal-field expectations, as well as quasi-one-dimensional bands and a spin-split saddle point at the zone center. The coexistence of competing magnetic interactions along different crystallographic directions suggests an inherent degree of frustration. ErPdPb thus provides a promising platform for exploring the interplay of frustration, anisotropy, and electronic structure in a twisted kagome lattice.

MXenes combine widely tunable electronic properties with promising chemical agility, yet Ti3C2Tx, the most studied member of this family, exhibits puzzling electronic and magnetic anomalies near room temperature. Here, we show that these effects arise from self-formed titanium suboxide domains, predominantly Ti3O5, stabilized within the MXene galleries. Employing comprehensive in situ structural, spectroscopic, thermodynamic, and transport analyses, we identify subtle but reproducible transitions at K and K. Raman microscopy and X-ray diffraction were used to track Ti3O5 polymorphism, while thermodynamic and transport signatures coincide with known transformations. Electron paramagnetic resonance reveals a marked anomaly in the Dysonian diffusion parameter without a considerable change in spin susceptibility, indicating reconfigured electronic pathways rather than carrier loss. These results reframe Ti3C2Tx as an inherently composite MXene-oxide system whose functional response is governed by minority suboxide phases. Beyond resolving a field-wide controversy, controlled oxidation emerges as a design lever to engineer phase-change behavior for thermal latching, opto-thermal switching, and robust, near-room-temperature MXene devices.

The Pauli limiting field imposed by the Zeeman effect bounds the upper critical field of weak-coupling superconductivity. It is determined by setting the condensation energy equal to the paramagnetic energy and scales inversely with the effective g-factor. Here, we demonstrate that in a few-layer-thick van der Waals superconductor, PdTe2, quantum confinement can tune the effective g-factor causing the Pauli limit to become thickness-dependent. We experimentally probe the in-plane upper critical field, Hc2∥, of PdTe2 at multiple intermediate thicknesses down to 20 mK. We find that Hc2∥ is enhanced by more than an order of magnitude as the thickness is reduced from 50 nm down to 17 nm. We model the temperature- and thickness-dependent Hc2||, revealing a thickness-dependent spin Zeeman depairing mechanism impacting its value. Our findings reveal how quantum confinement drives a reduction in g that enhances the Pauli limiting field and allows the measured enhancement of Hc2∥. A violation of the Pauli limit is often associated with unconventional pairing symmetry in superconductors. Our work demonstrates that this simple association is difficult without knowledge of the g-factor, particularly in layered materials.

The development of multifunctional solid-state materials is key to advancing lithium-ion batteries with enhanced safety and simplified architectures. Here, we report a scalable, highly efficient (near 100%), solvent-free mechanochemical synthesis of hexagonal boron nitride (hBN) functionalized with lithium oxalate (Li_2C_2O_4), yielding a novel lamellar composite that functions both as a lithium-ion conductor and separator. The high-energy milling process promotes exfoliation of hBN and covalent attachment of oxalate groups at edge and defect sites, forming a brown, nanocrystalline material with uniform lithium distribution. The composite exhibits room-temperature ionic and negligible electronic conductivity, thermal stability at least up to 350 ^∘C, and hosts stable free radicals enabling its use as a spin label. The synthesis produces no byproducts and can be extended towards lithium doping via secondary mechanochemical steps, creating highly doped, chemically stable phases that host additional Li for ionic conduction. These results introduce a new class of lithium-rich, boron nitride-based solids for solid-state batteries, combining ion conduction, mechanical robustness, and thermal resilience in a single material platform.

Kagome magnets represent a promising class of materials that exhibit intriguing electronic and magnetic properties, and they have recently garnered significant attention. While most kagome-lattice compounds are hexagonal, here we report the single-crystal growth and physical property measurements of similar compounds RFe_6Ge_6 (R = Y, Dy, Tb), which crystallize in an orthorhombic structure. The structure can be derived from a hexagonal prototype RFe_3Ge_2 by replacing every other R atom with a covalent Ge_2 dimer. Ordering of the latter makes the structure orthorhombic the kagome net slightly distorted, and the three Fe sites formally inequivalent. The iron and rare-earth sublattices order independently: the Fe moments order above 400 K having, with ferromagnetic Kagome planes stacked antiferromagnetically, while the rare-earth moments order below 9 K. While TbFe_6Ge_6 exhibits a single magnetic ordering transition associated with the Tb atoms, DyFe_6Ge_6 shows two distinct magnetic phase transitions, which are strongly influenced by crystal electric field effects on the Dy^3+ ions. Density functional theory (DFT) calculations show that the ferromagnetic ordering of the Fe planes is driven by a high density of states at the Fermi energy. They also reveals three dramatically different structural energy scales: R and Ge_2 form alternating 1D chains perpendicular to the kagome planes, and violating this alternation incurs a huge energy cost. Aligning these chains is less costly, and actual 2D order of anti-aligned chains costs very little. These compounds represent a unique class of materials, offering new possibilities to investigate the interplay between the distinct crystal lattice geometry and the underlying electronic and magnetic properties.

Altermagnets (AMs) are a new class of magnetic materials that combine the beneficial spintronics properties of ferromagnets and antiferromagnets, garnering significant attention recently. Here, we have identified altermagnetism in a layered intercalated transition metal diselenide, CoNb_4Se_8, which crystallizes with an ordered sublattice of intercalated Co atoms between NbSe_2 layers. Single crystals are synthesized, and the structural characterizations are performed using single crystal diffraction and scanning tunneling microscopy. Magnetic measurements reveal easy-axis antiferromagnetism below 168 K. Density functional theory (DFT) calculations indicate that A-type antiferromagnetic ordering with easy-axis spin direction is the ground state, which is verified through single crystal neutron diffraction experiments. Electronic band structure calculations in this magnetic state display spin-split bands, confirming altermagnetism in this compound. The layered structure of CoNb_4Se_8 presents a promising platform for testing various predicted properties associated with altermagnetism.

The kagome lattice, known for its strong frustration in two dimensions, hosts a variety of exotic magnetic and electronic states. A variation of this geometry, where the triangular motifs are twisted to further reduce symmetry, has recently revealed even more complex physics. HoAgGe exemplifies such a structure, with magnetic and electronic properties believed to be driven by strong in-plane anisotropy of the Ho spins, effectively acting as a two-dimensional spin ice. In this study, using a combination of magnetization, Hall conductivity measurements, and density functional theory calculations, we demonstrate how various spin-ice states, stabilized by external magnetic fields, influence the Fermi surface topology. More interestingly, we observe sharp transitions in Hall conductivity without concurrent changes in magnetization when an external magnetic field is applied along a particular crystallographic direction, underscoring the role of strong magnetic frustration and providing a new platform for exploring the interplay between magnetic frustration, electronic topology, and crystalline symmetry. These results also highlight the limitations of a simple spin-ice model, suggesting that a more sophisticated framework is necessary to capture the subtle experimental nuances observed.

Ti$_3$C$_2$T$_x$ is a leading compound within the MXenes family and can find host in widespread applications. It is synthesized by selectively etching layers from the Ti$_3$AlC$_2$ precursor, and this process typically introduces surface terminations, T$_x$, such as $-$OH, $=$O, or $-$F. However, the aggressive chemical conditions required for its preparation, as well as exposure to air, humidity, and heat, can lead to impurity phases that potentially compromise its desirable properties. We reveal a two-step oxidation process during heat treatment, where initial oxidation occurs between layers without altering the integrity of the Ti$_3$C$_2$ layered structure, followed by the formation of anatase TiO$_2$ at elevated temperatures. The process was carefully monitored using \emph{in situ} Raman spectroscopy and \emph{in situ} microwave conductivity measurements, employed to Ti$_3$C$_2$T$_x$ prepared using various etching techniques involving concentrated HF, LiF + HCl, and HF + HCl mixtures. The oxidation process is heavily influenced by the synthesis route and surface chemistry of Ti$_3$C$_2$T$_x$, with fluoride and oxyfluoride groups playing a pivotal role in stabilizing the anatase phase. The absence of these groups, in contrast, can lead to the formation of rutile TiO$_2$.

Ti3C2Tx is a leading compound within the MXenes family and can find host in widespread applications. It is synthesized by selectively etching layers from the Ti3AlC2 precursor, and this process typically introduces surface terminations, Tx, such as OH, O, or F. However, the aggressive chemical conditions required for its preparation, as well as exposure to air, humidity, and heat, can lead to impurity phases that potentially compromise its desirable properties. Herein, a two‐step oxidation process is revealed during heat treatment, where initial oxidation occurs between layers without altering the integrity of the Ti3C2‐layered structure, followed by the formation of anatase TiO2 at elevated temperatures. The process is carefully monitored using in situ Raman spectroscopy and in situ microwave conductivity measurements, applied to Ti3C2Tx prepared using various etching techniques involving concentrated hydrofluoric acid, LiF + HCl, and HF + HCl mixtures. The oxidation process is heavily influenced by the synthesis route and surface chemistry of Ti3C2Tx, with fluoride and oxyfluoride groups playing a pivotal role in stabilizing the anatase phase. The absence of these groups, in contrast, can lead to the formation of rutile TiO2.

The measurement and description of the charge-carrier lifetime (τc) is crucial for the wide-ranging applications of lead-halide perovskites. We present time-resolved microwave-detected photoconductivity decay (TRMCD) measurements and a detailed analysis of the possible recombination mechanisms including trap-assisted, radiative, and Auger recombination. We prove that performing injection-dependent measurement is crucial in identifying the recombination mechanism. We present temperature and injection level dependent measurements in CsPbBr3, which is the most common inorganic lead-halide perovskite. In this material, we observe the dominance of charge-carrier trapping, which results in ultra-long charge-carrier lifetimes. Although charge trapping can limit the effectiveness of materials in photovoltaic applications, it also offers significant advantages for various alternative uses, including delayed and persistent photodetection, charge-trap memory, afterglow light-emitting diodes, quantum information storage, and photocatalytic activity.

The discovery of an anomalous Hall effect (AHE) sensitive to the magnetic state of antiferromagnets can trigger a new era of spintronics, if materials that host a tunable and strong AHE are identified. Altermagnets are a new class of materials that can under certain conditions manifest a strong AHE, without having a net magnetization. But the ability to control their AHE is still lacking. In this study, we demonstrate that the AHE in altermagnetic α-MnTe grown on GaAs(111) substrates can be "written on-demand" by cooling the material under an in-plane magnetic field. The magnetic field controls the strength and the coercivity of the AHE. Remarkably, this control is unique to α-MnTe grown on GaAs and is absent in α-MnTe grown on SrF2. The tunability that we reveal challenges our current understanding of the symmetry-allowed AHE in this material and opens new possibilities for the design of altermagnetic spintronic devices.

For centuries, artisans have harnessed gold nanoparticles to imbue their creations with the vibrant hues that captivate the eye through interactions with visible light. In modern times, these distinct optoelectronic characteristics have pivoted toward the forefront of innovative technologies, finding their niche in advanced applications from solar energy to medicine, overshadowing their artistic heritage. This investigation reimagines the utilitarian scope of gold by innovating the optical characteristics of gold-titania nanostructures. This allows for an expanded palette of colors that retain the value of the precious metal. We employ nanostructured TiO2 in a high-pressure-high-temperature sintering technique that stabilizes Au nanoparticles, thwarting coalescence, and Oswald ripening. Further refinement is possible by engineering TiO2 color centers through the introduction of oxygen vacancies and Ti3+ ions, which aid in creating an opulent high-karat black-gold, but preserve the mechanical attributes essential to the integrity and function of the final product.

Coherent light sources emitting in the terahertz range are highly sought after for fundamental research and applications. Terahertz lasers rely on achieving population inversion. We demonstrate the generation of terahertz radiation using nitrogen-vacancy centers in a diamond single crystal. Population inversion is achieved through the Zeeman splitting of the S = 1 state in 15 tesla, resulting in a splitting of 0.42 terahertz, where the middle Sz = 0 sublevel is selectively pumped by visible light. To detect the terahertz radiation, we use a phase-sensitive terahertz setup, optimized for electron spin resonance (ESR) measurements. We determine the spin-lattice relaxation time up to 15 tesla using the light-induced ESR measurement, which shows the dominance of phonon-mediated relaxation and the high efficacy of the population inversion. The terahertz radiation is tunable by the magnetic field, thus these findings may lead to the next generation of tunable coherent terahertz sources.

Understanding the recombination lifetime of charge carriers () is essential for the diverse applications of photovoltaic materials, such as perovskites. The study on the inorganic perovskite, CsPbBr 3 , reveals recombination dynamics exceeding 1 ms below 200 K and approaching 100 μs at room temperature. Utilizing time‐resolved microwave‐detected photoconductivity decay in conjunction with injection dependence, it is found that is dominated by impurity charge trapping. The observed injection dependence is well corroborated by modeling of the trap mechanism. The ultralong decay time is also consistent with photoconductivity measurements with a continuous‐wave excitation at powers corresponding to around 1 Sun irradiation. While charge‐carrier trapping may, in theory, impose limitations on the photovoltaic efficiency of single‐cell devices, it can also contribute to increased efficiency in tandem cells and find applications in photodetection, photocatalysis, and quantum information storage.

Knowledge of the charge-carrier recombination lifetime, tau, is crucial for the various applications of photovoltaic perovskites. We studied the novel inorganic perovskite, CsPbBr3 and we observe recombination dynamics beyond 1 ms below 200 K and tau approaching 100 us at room temperature. Time-resolved microwave-detected photoconductivity decay (TRMCD), used in combination with injection dependence, evidence that tau is dominated by impurity charge trapping. The observed injection dependence is well corroborated by modeling of the trap mechanism. The ultra-long decay time is also consistent with photoconductivity measurements with a continuous-wave excitation at powers corresponding to around one Sun irradiation. While in principle charge-carrier trapping may limit the photovoltaic efficiency in single-cell photovoltaic devices, it could also lead to enhanced efficiency in tandem cells as well as for alternative applications including photodetection and quantum information storage.

Graphite has been intensively studied, yet its electron spins dynamics remains an unresolved problem even 70 years after the first experiments. The central quantities, the longitudinal ( T 1 ) and transverse ( T 2 ) relaxation times were postulated to be equal, mirroring standard metals, but T 1 has never been measured for graphite. Here, based on a detailed band structure calculation including spin-orbit coupling, we predict an unexpected behavior of the relaxation times. We find, based on saturation ESR measurements, that T 1 is markedly different from T 2 . Spins injected with perpendicular polarization with respect to the graphene plane have an extraordinarily long lifetime of 100 ns at room temperature. This is ten times more than in the best graphene samples. The spin diffusion length across graphite planes is thus expected to be ultralong, on the scale of ~ 70 μ m, suggesting that thin films of graphite — or multilayer AB graphene stacks — can be excellent platforms for spintronics applications compatible with 2D van der Waals technologies. Finally, we provide a qualitative account of the observed spin relaxation based on the anisotropic spin admixture of the Bloch states in graphite obtained from density functional theory calculations.