Abstract The generation and control of spin currents are crucial for advancing next-generation spintronic technologies. These technologies depend on materials capable of efficiently sourcing and interconverting spin and charge currents, while overcoming some limitations associated with conventional ferromagnets and heavy metals. Kagome topological antiferromagnetic Weyl semimetals, such as Mn3Sn, present unique advantages owing to their distinct magnetic order and significant Berry curvature-driven transport phenomena. In this study, we systematically investigate spin current generation and spin-to-charge conversion phenomena in epitaxial (0001)-oriented Mn3Sn thin films. Our findings reveal a moderate spin Hall angle of 0.9% and a nearly isotropic in-plane spin Hall conductivity of 44.4 (ℏ/e) Ω-¹.cm-¹ at room temperature, originating from a combination of intrinsic and extrinsic contributions, as discussed in light of first-principle calculations. Furthermore, in Mn3Sn(0001)/Ni81Fe19 heterostructures, we observe a high spin-mixing conductance of 28.52 nm-² and an interfacial spin-transparency of approximately 72%. Notably, we also find that the spin diffusion length in Mn3Sn(0001) epitaxial films exceeds 15 nm at room temperature. Our results highlight the potential, and limitations, of the topological Weyl noncollinear antiferromagnet Mn3Sn as an efficient material for spin transport and conversion in prospective spintronic applications.

Co2MnGa (CMG), a magnetic Weyl semimetal, exhibits high Curie temperature, ultralow damping, and strong spin-dependent transport properties, favorable for spintronics applications. While its room-temperature magnetization dynamics have been explored, the temperature (T ) dependence of key dynamic parameters such as damping and exchange stiffness remains underexplored. In this work, we investigate the temperature-dependent magnetization dynamics of sputtered CMG thin films (20, 60, and 80 nm) on MgO substrates. We use broadband ferromagnetic resonance spectroscopy with a magnetic field applied perpendicular to the sample plane to characterize these properties. X-ray diffraction reveals a strain-induced tetragonal distortion originating from the substrate-film lattice mismatch, most pronounced in the 20 nm film. As temperature decreases, the saturation magnetization (M-s) deviates from Bloch's law below 170 K, due to a temperature-dependent tetragonal distortion. Furthermore, the effective magnetization M-eff > M-s indicates a net in-plane anisotropy that strengthens with decreasing temperature, while the perpendicular uniaxial anisotropy (K-u[001]) also increases, with the 20 nm film exhibiting the highest values across all temperatures. Perpendicular standing spin waves observed in the 60 and 80 nm films enable extraction of the exchange stiffness (A(ex)) and exchange length (lex), both of which increase with decreasing temperature. Furthermore, Aexfollows a T-2 dependence indicative of a dominant contribution from electron-magnon interactions. Compared to the 80 nm film, the 60 nm film has a larger magnetic domain size as revealed by magnetic force microscopy. All films exhibit ultralow damping at room temperature, with the 80 nm film showing a temperature-independent behavior.

Topological defects play a crucial role across various fields, mediating phase transitions and macroscopic behaviors as they propagate through space. Their role as robust information carriers has also generated much attention. However, controlling their motion remains challenging, especially towards achieving motion along well-defined paths, which typically require predefined structural patterning. Here, we demonstrate the tunable, unidirectional motion of topological defects in a laterally unconfined thin film. The motion of these defects-specifically magnetic dislocations-is shown to mediate the overall continuous rotation of the stripe pattern in which they are embedded. We determine the connection between the unidirectional motion of dislocations and the underlying three-dimensional (3D) magnetic structure by performing 3D magnetic vectorial imaging with in situ magnetic fields. A minimal model for dislocations in stripe patterns that encodes the symmetry breaking induced by the external magnetic field reproduces the motion of dislocations that facilitate the 2D rotation of the stripes, highlighting the universality of the phenomenon. This work establishes a framework for studying the field-driven behavior of topological textures and designing materials that enable well-defined, controlled motion of defects in unconfined systems, paving the way to manipulate information carriers in higher-dimensional systems.

Femtosecond laser light can transfer spin angular momentum between magnetic subspecies that exhibit hybridized valence bands within an alloy or compound, and represents the fastest route for manipulating the magnetization of a material. To date, ultrafast spin transfer has predominantly been explained in terms of the initial and final states available for laser excitation. Here, by comparing the measured and calculated dynamics across the entire $M$-edges of two very similar Heusler compounds, $Co_2MnGa$ and $Co_2MnGe$ as well as a sample of elemental Co, we find that simply accounting for the initial and final electron states available for laser excitation cannot alone explain the experimental observations. The influence of spin lifetimes must also be included, due to the shifting of the Fermi level upon replacing Ga with Ge, or the presence of crystalline disorder. This explains why the ordered $L2_1$ phase of $Co_2MnGa$ demonstrates strong laser-induced magnetic signal enhancements across the entire Co-edge, while similar enhancements were not observed in partially disordered $Co_2MnGe$. Although intra-site spin-transfers were expected in the minority channel in pure Co due to the presence of many more available states in the minority channel above the Fermi level, no such signal was observed due to very short few-femtosecond spin lifetimes in a metal. Finally, we identify key regions in the magnetic asymmetry where a transiently enhanced signal could be misinterpreted as a light-induced spin-transfer signature.

Heterogeneous processes for enantiomeric processes based on inorganic crystals have been a topic of resurgent interest. However, it remains a challenge to answer the question of what the driving forces for the emergence of homochirality in nature and chemical reactions are. Here, we propose one possible driver of enantioselectivity, namely orbital angular momentum (OAM) polarization. Enantioselective recognition of 3,4-dihydroxyphenylalanine (DOPA) was achieved by using B20 group PdGa crystals with different chiral lattices. Orbital textures of PdGa enantiomers (namely PdGa-A and PdGa-B) suggest large OAM polarization for the bands near the Fermi level and carrying opposite signs. This leads to the difference in adsorption energy between PdGa chiral crystals and DOPA molecules, depending on the pairing ability between the O 2p and Pd 4d orbital. These results provide a new route to achieving enantioselectivity with pure inorganic crystals and may hold an answer to the origin of chirality in nature.

The rise of nonmagnetic topological semimetals, which provide a promising platform for observing and controlling various spin-orbit effects, has led to significant advancements in the field of topological spintronics. RhSi exists in two distinct polymorphs: cubic and orthorhombic crystal structures. The noncentrosymmetric B20 cubic structure has been extensively studied in the bulk for hosting unconventional multifold Fermions. In contrast, the orthorhombic structure, which crystallizes in the Pnma space group (No. 62), remains less explored and belongs to the family of topological Dirac semimetals. In this work, we investigate the structural, magnetic, and electrical properties of RhSi textured-epitaxial films grown on Si(111) substrates, which crystallize in the orthorhombic structure. We investigate the efficiency of pure spin current transport across RhSi/permalloy interfaces and the subsequent spin-to-charge current conversion via inverse spin Hall effect measurements. The experimentally determined spin Hall conductivity in orthorhombic RhSi reaches a maximum value of 126 ℏe(Ω·cm)-1 at 10 K, which aligns reasonably well with first-principles calculations that attribute the spin Hall effect in RhSi to the spin Berry curvature mechanism. Additionally, we demonstrate the ability to achieve a sizable spin-mixing conductance (34.7 nm-2) and an exceptionally high interfacial spin transparency of 88% in this heterostructure, underlining its potential for spin-orbit torque switching applications. Overall, this study broadens the scope of topological spintronics, emphasizing the controlled interfacial spin-transport processes and subsequent spin-to-charge conversion in a previously unexplored topological Dirac semimetal RhSi/ferromagnet heterostructure.

Magnetic Weyl semimetals are emerging as a new class of material systems for spintronics due to their intrinsic topological properties and the inherent interplay between topology and magnetism, giving rise to novel electronic states and spin-orbital-related effects. Here, ultrafast magnetization dynamics in the Weyl semimetal Heusler ferromagnet Co2MnGa is investigated, from femtosecond to nanosecond timescales, using time-resolved magneto-optical Kerr effect (TR-MOKE) at room temperature. Ultrafast demagnetization and precessional dynamics corresponding to the Kittel and perpendicular standing spin-wave (PSSW) modes of Co2MnGa, interfaced with Pt thin films of varying thickness, have been investigated. The exchange stiffness constant of Co2MnGa is determined, as well as detailed information about spin-transport across the Co2MnGa/Pt interface. From the modulation of Gilbert damping of Co2MnGa with Pt thickness, a very high intrinsic spin-mixing conductance, G(up arrow down arrow) = 1.73 x 10(16) cm(-2) is extracted of the interface and the spin diffusion length of Pt is determined to be 2.9 +/- 0.2 nm. The interfacial spin transparency is found to reach a sizeable value of approximate to 83%, in the perfect spin-sink regime, suggesting the great potential of this heterostructure for spin-orbitronics and devices relying on ultrafast magnetization dynamics.

The rise of non-magnetic topological semimetals, which provide a promising platform for observing and controlling various spin-orbit effects, has led to significant advancements in the field of topological spintronics. RhSi exists in two distinct polymorphs: cubic and orthorhombic crystal structures. The noncentrosymmetric B20 cubic structure has been extensively studied for hosting unconventional multifold fermions. In contrast, the orthorhombic structure, which crystallizes in the Pnma space group (No. 62), remains less explored and belongs to the family of topological Dirac semimetals. In this work, we investigate the structural, magnetic, and electrical properties of RhSi textured-epitaxial films grown on Si(111) substrates, which crystallize in the orthorhombic structure. We investigate the efficiency of pure spin current transport across RhSi/permalloy interfaces and the subsequent spin-to-charge current conversion via inverse spin Hall effect measurements. The xperimentally determined spin Hall conductivity in orthorhombic RhSi reaches a maximum value of 126 ($\hbar$/e)($\Omega$.cm)$^{-1}$ at 10 K, which aligns reasonably well with first-principles calculations that attribute the spin Hall effect in RhSi to the spin Berry curvature mechanism. Additionally, we demonstrate the ability to achieve a sizable spin-mixing conductance (34.7 nm$^{-2}$) and an exceptionally high interfacial spin transparency of 88$%$ in this heterostructure, underlining its potential for spin-orbit torque switching applications. Overall, this study broadens the scope of topological spintronics, emphasizing the controlled interfacial spin-transport processes and subsequent spin-to-charge conversion in a previously unexplored topological Dirac semimetal RhSi/ferromagnet heterostructure.

Conventionally, the modulation of the intrinsic Weyl nodes in Weyl semimetals is challenging, due to topological protection. Here we report the structural dependence of the Weyl nodes in a Co2MnGa Heusler thin film via a temperature-dependent tetragonal distortion. The ability to manipulate these Weyl nodes allows for the control of the intrinsic electromagnetic properties. Temperature-dependent x-ray diffraction (XRD) measurements identify a compressive tetragonal distortion with decreasing temperature from 300 to 20 K. The calculated Weyl properties can be directly compared with experimental parameters through the temperature-dependent XRD measurements which show the intrinsic correlation between Weyl properties and important magnetic parameters. The microscopic momentum space properties of Weyl nodes such as the distance (dW), solid angle (QW), tilt (cpW), and nodal point energy (EW) directly affect the macroscopic observable properties such as exchange stiffness (A), magnetization (M), and effective anisotropy field (HKeff), as shown via structure-dependent density functional theory calculations. These predictions are experimentally observed as large variations in the bulk magnetization and effective anisotropy field as a function of temperature. These results highlight a unique degree of freedom in the control of macroscopic magnetic properties via the modulation of the intrinsic properties of Weyl nodes through structural distortions.

Metallic antiferromagnets with chiral spin textures induce Berry curvature-driven anomalous and spin Hall effects that arise from the topological structure of their electronic bands. Here, we use epitaxial engineering to stabilize (111)-oriented thin films of Mn3Ge with a cubic phase. This cubic phase is distinct from tetragonal ferrimagnetic and hexagonal noncollinear antiferromagnetic structures with the same chemical composition. First-principles calculations indicate that cubic Mn3Ge will preferentially form an all-in/all-out triangular spin texture. We present evidence for this noncollinear antiferromagnetism through magnetization measurements with a Néel temperature of 490 K. First-principles calculations of the corresponding band structure indicate the presence of Weyl points. These highlight cubic Mn3Ge as a candidate material for topological antiferromagnetic spintronics.

This study introduces a novel magnetic nanohybrid material consisting of ferromagnetic (FM) bcc Fe–Co nanoparticles (NPs) grown on nanodiamond (ND) nanotemplates. A combination of wet chemistry, which produces chemical precursors and their subsequent thermal treatment under vacuum, was utilized for its development. The characterization and study of the prepared samples performed with a range of specialized experimental techniques reveal that thermal treatment of the as-prepared hybrid precursors under a range of annealing conditions leads to the development of Co-rich Fe–Co alloy NPs, with average sizes in the range of 6–10 nm, that exhibit uniform distribution on the surfaces of the ND nanotemplates and demonstrate FM behavior throughout a temperature range from 2 K to 400 K, with maximum magnetization values ranging between 18.9 and 21.1 emu/g and coercivities ranging between 112 and 881 Oe. Moreover, 57Fe Mössbauer spectroscopy reveals that apart from the predominant bcc FM Fe–Co phase, iron atoms also participate in the formation of a secondary martensitic-type Fe–Co phase. The emergence of this distinctive phase is attributed to the diffusion of carbon atoms within the Fe–Co lattices during their formation at elevated temperatures. The source of these carbon atoms is related to the unique morphological properties of the ND growth matrices, which facilitate surface sp2 formations. Apart from their diffusion within the Fe–Co NP lattice, the carbon atoms also reconstruct layered graphitic-type nanostructures enveloping the metallic alloy NPs. These non-typical nanohybrid materials, reported here for the first time in the literature, hold significant potential for use in applications related, but not limited to, biomedicine, biopharmaceutics, catalysis, and other various contemporary technological fields.

Topological materials occupy an important place in the quantum materials family due to their peculiar low-energy electrodynamics, hosting emergent magneto-electrical, and nonlinear optical responses. This manuscript reports on the optical responses for the magnetic topological nodal semimetal Co2MnGa, studied in a thin film geometry at various thicknesses. The thickness-dependent optical conductivity is investigated, observing a substantial dependence of the electronic band structure on thickness. Additionally, details on the ultrafast response of the low energy excitations in the terahertz frequency are reported by employing optical pump-terahertz probe (OPTP) spectroscopy. In particular, the photocarrier dynamics of Co2MnGa thin films is studied at varying pump fluence, pump wavelength, and film thickness, observing a negative THz photoconductivity which is assigned to a dynamical formation of large polarons in the material.

In the unconventional superconductor Sr$_2$RuO$_4$, uniaxial stress along the $[100]$ direction tunes the Fermi level through a Van Hove singularity (VHS) in the density of states, causing a strong enhancement of the superconducting critical temperature $T_\textrm{c}$. Here, we report measurements of the London penetration depth $\lambda$ as this tuning is performed. We find that the zero-temperature superfluid density, here defined as $\lambda(0)^{-2}$, increases by $\sim$15%, with a peak that coincides with the peak in $T_\textrm{c}$. We also find that the low temperature form of $\lambda(T)$ is quadratic over the entire strain range. Using scanning tunneling microscopy, we find that the gap increases from $\Delta_0 \approx 350~\mu$eV in unstressed Sr$_2$RuO$_4$ to $\Delta_0 \approx 600~\mu$eV in a sample strained to near the peak in $T_c$. With a nodal order parameter, an increase in the superconducting gap could bring about an increase in the superfluid density through reduced sensitivity to defects and through reduced non-local effects in the Meissner screening. Our data indicate that tuning to the VHS increases the gap throughout the Brillouin zone, and that non-local effects are likely more important than reduced scattering.

Half-metallic half-Heusler compounds with strong spin-orbit-coupling and broken inversion symmetry in their crystal structure are promising materials for generating and absorbing spin-currents, thus enabling the electric manipulation of magnetization in energy-efficient spintronic devices. In this work, we report the spin-to-charge conversion in sputtered ultrathin films of the half-Heusler compound MnPtSb with thickness (t) in the range from 1 to 6 nm. A combination of X-ray and transmission electron microscopy measurements evidence the epitaxial nature of these ultrathin non-centrosymmetric MnPtSb films, with a clear (111)-orientation obtained on top of (0001) single-crystal sapphire substrates. The study of the thickness (t)-dependent magnetization dynamics of the MnPtSb(t)/Co(5nm)/Au(5nm) heterostructure revealed that the MnPtSb compound can be used as an efficient spin current generator, even at film thicknesses as low as 1 nm. By making use of spin pumping FMR, we measure a remarkable t-dependent spin-charge conversion in the MnPtSb layers, which clearly demonstrate the interfacial origin of the conversion. When interpreted as arising from the inverse Edelstein effect (IEE), the spin-charge conversion efficiency extracted at room temperature for the thinnest MnPtSb layer reaches {\lambda}IEE~3 nm, representing an extremely high spin-charge conversion efficiency at room temperature. The still never explored ultrathin regime of the MnPtSb films studied in this work and the discover of their outstanding functionality are two ingredients which demonstrate the potentiality of such materials for future applications in spintronics.

We present an optical pump-THz emission study on non-collinear antiferromagnet Mn_3Sn. We show that Mn_3Sn acts as a source of THz radiation when irradiated by femtosecond laser pulses. The polarity and amplitude of the emitted THz fields can be fully controlled by the polarisation of optical excitation. We explain the THz emission with the photocurrents generated via the photon drag effect by combining various experimental measurements as a function of pump polarisation, magnetic field, and sample orientation with thorough symmetry analysis of response tensors.

Two-dimensional (2D) van der Waals (vdW) ferromagnetic metals FexGeTe2 with x = 3-5 have raised significant interest in the scientific community. Fe5GeTe2 shows prospects for spintronic applications since the Curie temperature Tc has been reported near or higher than 300 K. In the present work, epitaxial Fe5-δGeTe2 (FGT) heterostructures were grown by Molecular Beam Epitaxy (MBE) on insulating crystalline substrates. The FGT films were combined with Bi2Te3 topological insulator (TI) aiming to investigate the possible beneficial effect of the TI on the magnetic properties of FGT. FGT/Bi2Te3 films were compared to FGT capped only with AlOx to prevent oxidation. SQUID and MOKE measurements revealed that the growth of Bi2Te3 TI on FGT films significantly enhances the saturation magnetization of FGT as well as the Tc well above room temperature (RT) reaching record values of 570 K. First-principles calculations predict a shift of the Fermi level and an associated enhancement of the majority spin (primarily) as well as the total density of states at the Fermi level suggesting that effective doping of FGT from Bi2Te3 could explain the enhancement of ferromagnetism in FGT. It is also predicted that strain induced stabilization of a high magnetic moment phase in FGT/Bi2Te3 could be an alternative explanation of magnetization and Tc enhancement. Ferromagnetic resonance measurements evidence an enhanced broadening in the FGT/Bi2Te3 heterostructure when compared to FGT. We obtain a large spin mixing conductance of g↑↓eff = 4.4 × 1020 m-2, which demonstrates the great potential of FGT/Bi2Te3 systems for spin-charge conversion applications at room temperature.

The study of heterogeneous reactions for enantiomeric processes based on inorganic crystals has been resurgent in recent years. However, the question remains how homochirality develops in nature and chemical reactions. Here, the successful growth of B20 group PdGa single crystals with different chiral lattices enabled us to achieve enantioselective recognition of 3,4-dihydroxyphenylalanine (DOPA) based on a new mechanism, namely orbital angular momentum (OAM) polarization. The orbital textures of PdGa crystals indicate large OAM polarization near the Fermi level and carrying opposite signs. A positive or negative magnetization in the [111] direction is expected depending on the chiral lattice of PdGa crystals. Due to this, the adsorption energies of PdGa crystals and DOPA molecules differ depending on how well the O-2p orbital of DOPA pairs with the Pd-4d orbital of PdGa. The results provide one possible explanation for how chirality arises in nature by providing an enantioselective route with pure inorganic crystals.

In this work, we present the experimental observation of helicity-dependent ultrafast photocurrents in a Mn3Sn film using optical pump-Terahertz emission spectroscopy. The magnitude and direction of photocurrents depend on the polarisation of the pump pulse and the optical incidence angle, but have no dependence on the magnetic field. We combine experimental results with a thorough symmetry analysis to argue that the helicity-dependent photocurrents arise predominantly from the circular photon drag effect.

Nonmagnetic topological semimetals that combine chirality in real and momentum spaces host unconventional multifold fermions and exhibit exotic electronic and optical properties endowed by their topologically nontrivial electronic band structure. Although the synthesis of nonmagnetic chiral single crystals with a noncentrosym-metric cubic B20 structure is well established, their heteroepitaxial growth in crystalline thin films remains a notable challenge. In this study, we present the structural, magnetic, and electrical magnetotransport properties of 24-and 51-nm-thick films of a B20-RhSi stoichiometric compound grown by magnetron sputtering. RhSi crystalline thin films on Si (111) single-crystal substrates exhibit a preferred (111) orientation with twin domains. The RhSi films display a nonmagnetic ground state, and their electrical resistivity demonstrates a clear and nonsaturating metallic behavior from 300 to 5 K. Magnetotransport measurements reveal that hole-type carriers dominate the Hall response with multiband contributions to electronic transport in the system. The good agree-ment with the Bloch-Gruneisen model and our first-principles calculations confirms that temperature-dependent electrical resistivity is governed by electron-phonon scattering. The ability to grow textured-epitaxial thin films of nonmagnetic B20 chiral topological semimetals is an important step toward accessing and controlling their remarkable topological surface states for designing chiraltronic devices with novel optoelectronic or spintronic functionalities.