Magnetic kagome metals host complex electronic states and real-space magnetic textures, but their small and temperature-dependent magnetic domains make experimental access difficult. Here we show that micro-focused circular-dichroic photoemission spectroscopy enables spectroscopic access to individual magnetic domains in the kagome metal DyMn6Sn6 at low temperature. By tuning to element-specific electronic states, we image domain contrast associated with Dy 4f levels and detect corresponding signatures from Mn core states. The energy dependence of the dichroic response is consistent with modeling and indicates ferrimagnetic alignment between Dy and Mn local moments. Measurements of Mn 3d-derived valence bands, supported by first-principles calculations, reveal features related to orbital magnetization. These results establish element- and orbital-resolved spectroscopy of single magnetic domains and enable studies of magnetic textures and electronic structure in complex magnetic quantum materials.

The magnetic structures of Ba3RRu2O9 (R = Tb, Er) have been investigated using high-intensity neutron powder diffraction (NPD) supported by dc and ac susceptibility studies. The NPD data reveal antiferromagnetic (AFM) ground states below TN similar to 9.8 and 6 K in Ba3TbRu2O9 and Ba3ErRu2O9, respectively, consistent with the magnetic transitions observed in dc and ac susceptibility measurements. In Ba3TbRu2O9, the magnetic structure is characterized by a propagation vector, k = (0, 0, 0), where Tb and Ru order ferromagnetically in the ab plane. Neighboring planes of Tb are coupled antiferromagnetically along the c direction as are neighboring planes of Ru, which leads to an AFM order between Tb and Ru as well. In contrast, the magnetic structure of Ba3ErRu2O9 is characterized by k = (0.5, 0, 0), with Er and Ru moments exhibiting a canted AFM ordering. Interestingly, the collinear (noncollinear) AFM order of Tb (Er) accompanied by the collinear (noncollinear) magnetic order of Ru in Ba3TbRu2O9 (Ba3ErRu2O9) along with the concurrent ordering of the rare earth and Ru in both compounds suggests a strong coupling between 4 f and 4d electrons. Both compounds show weak magnetic ordering above TN similar to that reported for Ba3HoRu2O9. We have understood this intriguing feature by preparing a Ba3ErRu2O9 sample with 3% excess RuO2. Our analysis suggests that the weak magnetic ordering above TN is strongly dependent on the excess RuO2; however, and interestingly, the magnetic structure below TN is robust against this RuO2 surplus. Our detailed study provides insights into the magnetic ground states of these two compounds, thereby enhancing the understanding of magnetic ordering in this fascinating family.

layered honeycomb magnet alpha-RuCl3 has attracted intense scrutiny as a prime candidate for realizing the Kitaev quantum spin liquid, yet a consensus on its microscopic Hamiltonian remains elusive due to the material's extreme sensitivity to structural details. Here, we report a comprehensive reexamination of the low-temperature crystallographic and magnetic structures of high-quality alpha-RuCl3 single crystals using unpolarized and polarized neutron diffraction. We confirm a sharp, first-order structural phase transition to the rhombohedral R3 & strns; space group with a pronounced thermal hysteresis. Crucially, using both spherical and longitudinal neutron polarization analysis, we determine the 3D orientation of the ordered magnetic moment without the ambiguity typically arising from domain distributions. We find that the Ru3+ magnetic moments in the zigzag phase are tilted by 15.7 degrees out of the hexagonal plane and, remarkably, exhibit an additional in-plane twist of -13.8 degrees. This "tilted and twisted" geometry differentiates the ground state from the previously reported models based on unpolarized neutron diffraction or resonant elastic X-ray scattering (REXS) analysis.

Kagome spin ice is an intriguing class of spin systems constituted by in-plane Ising spins with ferromagnetic interaction residing on the kagome lattice, theoretically predicted to host a plethora of magnetic transitions and excitations. In particular, different variants of kagome spin ice models can exhibit different sequences of symmetry breaking upon cooling from the paramagnetic to the fully ordered ground state. Recently, it has been demonstrated that the frustrated intermetallic HoAgGe stands as a faithful solid-state realization of kagome spin ice. However, whether any of the established symmetry-breaking pathways apply to this material remains unaddressed. Here, we use single-crystal neutron diffuse scattering to map the spin ordering of HoAgGe at various temperatures more accurately; surprisingly, we find that the ordering sequence appears to be different from previously known scenarios: From the paramagnetic state, the system first enters a partially ordered state with fluctuating magnetic charges, in contrast to a charge-ordered paramagnetic phase, before reaching the fully ordered state. Through Monte Carlo simulations and scaling analyses using an extended three-dimensional (3D) spin model for the distorted kagome spin ice in HoAgGe, we elucidate a single 3D XY phase transition into the ground state with broken time-reversal symmetry (TRS). However, the 3D XY transition has a long crossover tail before the fluctuating magnetic charges fully order. More interestingly, we find, both experimentally and theoretically, that the TRS-breaking phase of HoAgGe features an unusual, hysteretic response: Despite their vanishing magnetization, the two time-reversal partners are distinguished and selected by a nonlinear magnetic susceptibility tied to the kagome ice rule. Our discovery not only unveils a new symmetry-breaking hierarchy of kagome spin ice but also demonstrates the potential of TRS-breaking frustrated spin systems for information technology applications.

High-quality single crystals of the two-dimensional van der Waals ferromagnet Fe3GaTe2 (FGaT) were successfully grown using the chemical vapour transport method, which effectively reduced surface impurities compared with conventional self-flux growth. Structural and magnetic characterizations were per-formed using single-crystal X-ray and neutron diffraction. The results confirm that FGaT crystallizes in the hexagonal P63/mmc structure, with Fe occupying two inequivalent sites (Fei and Feii), where the magnetic moment of Fei [1.9 (2) μB] is larger than that of Feii [1.4 (6) μB]. The magnetic easy axis is oriented along the c axis and the Curie temperature (T C) is approximately 355-360 K. Compared with Fe3GeTe2 (FGT), FGaT exhibits a slightly expanded a axis and a contracted c axis, resulting in a reduction in the Fei-Fei interatomic distance along the c axis. This pronounced contraction could strengthen the Fe-Fe exchange interaction, which is believed to be the key factor responsible for the significantly higher T C in FGaT relative to FGT.

V-based kagome metals exhibit a unique lattice geometry that can give rise to exotic electronic and magnetic phenomena, making them an ideal platform to study the interplay of topology and magnetism. We present a combined thermodynamic and muon spin relaxation (& micro;SR) investigation of single-crystal RV6Sn6 (R = Tb, Dy, Ho, Er) compounds, focusing on their low-temperature magnetic behavior. Heat-capacity and & micro;SR measurements reveal distinct magnetic phase transitions below 4 K, confirming the emergence of long-range magnetic order in all compounds studied. The & micro;SR results further indicate persistent spin fluctuations within the magnetically ordered state down to 50 mK, reflected in reduced ordered moments obtained from a hyperfine analysis of the heat-capacity measurements. These findings uncover the coexistence of static and dynamic magnetism in V-based kagome metals and emphasizing the key role of 4f-electron anisotropy in shaping their magnetic ground states. Compared with the Mn-based RMn6Sn6 analogs, our results highlight the unique magnetism arising from the decoupled rare-earth sublattice and its interplay with the nonmagnetic V kagome network.

Microscopic spin-textures in two-dimensional van der Waals (vdW) ferromagnets, particularly Fe3GaTe2 (FGaT), offer strong potential for spintronic applications due to their high Curie temperature, stable perpendicular magnetic anisotropy, and the critical importance of controllable magnetic properties. FGaT crystals with thicknesses ranging from 150 nm to 2 mu m exhibit robust stripe, bubble, and complex magnetic textures during field cooling, with domain size systematically increasing with cooling-field strength. The resulting bubble and mixed-domain states remain stable above 2000 Oe at room temperature, reflecting the intrinsic stability of vdWmediated spin textures. External magnetic fields tune bubble size through reversible expansion or contraction, and hexagonal bubble ordering emerges through field-induced splitting and shape transformations. Domain annihilation and merging processes are also observed. Micromagnetic simulations reproduce the field-driven evolution and reveal size-and time-dependent dynamics consistent with experiment. These findings provide critical insights into the field-tunable magnetic behavior of FGaT and highlight its potential in spintronic applications, particularly for domain manipulation and corresponding spin transport properties.

The three-dimensional pyrochlore lattice of corner-sharing tetrahedra can host a quantum spin ice, a quantum analogue of the classical spin ice found in other pyrochlore compounds. This state can manifest a quantum spin liquid, and indeed, these compounds are predicted to have emergent gauge fields that produce linearly dispersing collective magnetic excitations near zero energy, in addition to the presence of higher-energy spinon excitations. Here we use polarized neutron scattering experiments on single crystals of the Ce2Zr2O7 pyrochlore. We find evidence for magnetic excitations near zero energy, in addition to signatures of spinons at higher energies. Furthermore, we perform heat capacity measurements and find behaviour consistent with the cubic-in-temperature dependence expected for linearly dispersing gapless bosonic modes. Comparing the observed magnetic excitations with theoretical calculations, we argue that Ce2Zr2O7 is a strong candidate for a dipolar-octupolar quantum spin ice with dominant dipolar Ising interactions.

Recent years have witnessed a steady progress towards blending two-dimensional quantum materials into technology, with future applications often rooted in the electronic structure. Since crossings and inversions of electronic bands with different orbital characters determine intrinsic quantum transport properties, knowledge of the orbital character is essential. Here, we benchmark angle-resolved photoelectron emission spectroscopy (ARPES) as a tool to experimentally derive orbital characters. For this purpose we study the valence electronic structure of two technologically relevant quantum materials, graphene and WSe2, and focus on circular dichroism that is believed to provide sensitivity to the orbital angular momentum. We analyze the contributions related to angular atomic photoionization profiles, interatomic interference, and multiple scattering. Regimes in which initial-state properties could be disentangled from the ARPES maps are critically discussed and the potential of using circular dichroic ARPES as a tool to investigate the spin polarization of initial bands is explored. For the purpose of generalization, results from two additional materials, GdMn6Sn6 and PtTe2, are presented in addition. This research demonstrates rich complexity of the underlying physics of circular dichroic ARPES, providing insights that will shape the interpretation of both past and future circular-dichroic ARPES studies.

Spin- and orbital-resolved access to the electronic bands is necessary to establish key properties of quantum materials such as the quantum-geometric tensor. Despite recent revival on magnetic Kagome compounds, no spectroscopic access to their magnetic properties has been available so far due to small domain sizes and lack of appropriate techniques. Furthermore, their real space magnetic texture is often complex and temperature-dependent. We investigate the magnetic Kagome metal DyMn_6Sn_6 using high-resolution micro-focused circular-dichroic angle-resolved photoemission (μ-CD-ARPES) to probe its magnetic and electronic properties. By tuning the kinetic energy to various features of the Dy 4f multiplet, we resolve magnetic domains in samples cryo-cooled down to 20 K. Smaller, but clear signatures are detected in the Mn 3p levels. The behavior of both Dy 4f and Mn 3p features are in remarkable agreement with our modeling based on the Hartree-Fock method, revealing ferrimagnetic alignment of Dy and Mn local moments, and further strengthening our interpretation. Adjusting the energy to the Mn 3d-dominated valence bands reveals signatures which we relate to the orbital magnetization through a comparison to ab initio electronic structure calculations. Our study establishes the spectroscopic access to a single magnetic domain in a Kagome metal, paving the way for further research into imaging magnetic phases of novel magnetic materials using μ-CD-ARPES.

Kagome spin ice is an intriguing class of spin systems constituted by in-plane Ising spins with ferromagnetic interaction residing on the kagome lattice, theoretically predicted to host a plethora of magnetic transitions and excitations. In particular, different variants of kagome spin ice models can exhibit different sequences of symmetry breaking upon cooling from the paramagnetic to the fully ordered ground state. Recently, it has been demonstrated that the frustrated intermetallic HoAgGe stands as a faithful solid-state realization of kagome spin ice. Here we use single crystal neutron diffuse scattering to map the spin ordering of HoAgGe at various temperatures more accurately and surprisingly find that the ordering sequence appears to be different from previously known scenarios: From the paramagnetic state, the system first enters a partially ordered state with fluctuating magnetic charges, in contrast to a charge-ordered paramagnetic phase before reaching the fully ordered state. Through state-of-the-art Monte Carlo simulations and scaling analyses using a quasi-2D model for the distorted Kagome spin ice in HoAgGe, we elucidate a single three-dimensional (3D) XY phase transition into the ground state with broken time-reversal symmetry (TRS). However, the 3D XY transition has a long crossover tail before the fluctuating magnetic charges fully order. More interestingly, we find both experimentally and theoretically that the TRS breaking phase of HoAgGe features an unusual, hysteretic response: In spite of their vanishing magnetization, the two time-reversal partners are distinguished and selected by a nonlinear magnetic susceptibility tied to the kagome ice rule. Our discovery not only unveils a new symmetry breaking hierarchy of kagome spin ice, but also demonstrates the potential of TRS-breaking frustrated spin systems for information technology applications.

The negative magnetization and exchange bias phenomena have been the subject of interest due to their promising applications in spintronic devices. In this study, we have comprehensively investigated these two intertwined magnetic phenomena in La1−xPrxCrO3 (x=0.8−0.9) compounds. The Cooke's model fit to dc magnetization data infers negative internal magnetic field for x=0.8, 0.85, and 0.87 and positive for x=0.9. The crossover of internal magnetic field from negative to positive across x=0.87 and its dominance over the external applied magnetic field leads to the magnetization switching from negative to positive. The internal magnetic field behavior also explains the anomalous magnetization behavior involving reduced magnetization for x=0.87, despite having higher Pr3+ concentration than that for x=0.8 and 0.85. The anomalous magnetization is corroborated well by the neutron depolarization experiments, where no depolarization is observed for x=0.87 owing to nearly compensated domain magnetization. Remarkably, a switching of the exchange bias from inverse (with positive HEB) to conventional (with negative HEB) due to a competition of external and internal magnetic fields is found in x=0.8 and 0.85 compounds. The x=0.87 and 0.9 compounds, on the other hand, show only conventional exchange bias at all measured magnetic fields. Using the Cooke's model, we show that the antiferromagnetic coupling between polarized Pr3+ and weak ferromagnetic component of canted Cr3+ moments explain not only the inverse exchange bias but the conventional exchange bias as well, however, the moment orientations are different for both types of exchange bias. Moreover, our study demonstrates that the ferromagnetic coupling between the two moments can also lead to conventional exchange bias, similar to that observed in interfacial heterostructure systems. Published by the American Physical Society 2025

A Dirac quantum spin liquid hosts Dirac spinons, which are low-energy fractionalized neutral quasiparticles with spin 1/2 that obey the Dirac equation. Recent inelastic neutron scattering studies have revealed cone spin continuum in YCu$_3$(OD)$_6$Br$_2$[Br$_{x}$(OD)$_{1-x}$], consistent with the convolution of two Dirac spinons. In this work, we further studied spin excitations using the inelastic neutron scattering technique. The width of low-energy spin excitations shows a linear temperature dependence, which can be explained by spinon-spinon interactions with a Dirac dispersion. Polarized neutron scattering measurements reveal that in-plane magnetic fluctuations are about 1.5 times stronger than the out-of-plane ones, suggesting the presence of Dzyaloshinskii-Moriya interaction and consistent with our theoretical modeling and simulations. Moreover, the high-energy spin excitations around 14 meV agree with the one-pair spinon-antispinon excitations in Raman studies. The real part of the dynamical susceptibility derived from the Kramers-Kronig relationship also accords with the Knight shift measured by nuclear magnetic resonance, clearly demonstrating the negligible effects of magnetic impurities on static susceptibility. These results provide a rare example in studying quantum-spin-liquid materials where different experimental techniques can be directly compared and give further insights for the possible Dirac quantum spin liquid in this system.

Polarized neutron scattering experiments reveal anisotropy of magnetic correlations in the candidate Kitaev material α-RuCl_{3}. The anisotropy of the inelastic response at the magnetic Bragg positions is opposite to the expectation for a simple Heisenberg model. Near the antiferromagnetic propagation vector, there are no low-energy transversal magnon modes and the response is always uniaxially polarized. These observations directly prove the fully anisotropic and bond-directional character of the magnetic interaction in α-RuCl_{3}. However, other findings disagree with a simple or strongly dominant Kitaev component.

This study demonstrates the localized creation of bubble domains in the two-dimensional (2D) ferromagnetic material Fe₃GaTe₂ using conductive atomic force microscopy. By applying bias voltage to the tip under a perpendicular magnetic field, sufficient current is generated to induce localized Joule heating, transforming random stripe domains into bubble domains. The bubble domains were successfully induced under ambient conditions at room temperature and remained stable, as confirmed by magnetic force microscopy. For Fe₃GaTe₂ layers with thicknesses of 1 μm, 200 nm, and 100 nm, the average diameters of bubble domains were measured at 620 ± 100 nm, 325 ± 80 nm, and 230 ± 70 nm, respectively, approximately 20 % larger than the pristine stripe width. By optimizing parameters such as bias voltage, application duration, and tip temperature based on Fe₃GaTe₂ thickness, the induced bubble domain density could be precisely controlled, ranging from few bubble domains within areas < 5 μm² to nearly 10⁴ bubble domains within 1200 μm². Furthermore, multi-point triggering demonstrated the re-writability of the domain structures, with non-overlapping domains remaining unaffected. These findings offer critical insights into the tunability of magnetic textures in 2D ferromagnets, providing a foundation for developing next-generation spintronic devices based on 2D heterostructures.

Magnetic kagome metals have attracted tremendous research interests recently, because they represent an ideal playground for exploring the fascinating interplay between their intrinsically inherited topologically nontrivial electron band structures, magnetism and electronic correlation effects, and the resultant novel electronic/magnetic states and emergent excitations. In this work, we report a comprehensive single-crystal neutron diffraction investigation of the ground-state magnetic structures of the recently discovered V-based topological kagome metals RV6Sn6 (R = Tb, Dy, Ho, Er). Furthermore, the sample synthesis details and our systematic studies of crystal structure, low-temperature magnetic and thermodynamic properties of these compounds via various in-house characterization techniques are also reported. Our single-crystal neutron diffraction measurements confirm that the long-range magnetic order forms below 4.3 K for R = Tb, 3.0 K for R = Dy, 2.4 K for R = Ho, and 0.6 K for R = Er, respectively. The ground-state magnetic structures of the studied compounds are comprehensively determined via the magnetic crystallography approaches. It can be revealed that RV6Sn6 (R = Tb, Dy, Ho) have a collinear ferromagnetic order in the ground state, with the ordered magnetic moment aligned along the c axis for R = Tb, Ho, while approximately 20 degrees tilted off from the c axis for R = Dy. In contrast, ErV6Sn6 shows an A-type antiferromagnetic structure with a magnetic propagation vector k = (0, 0, 0.5), and with the ordered magnetic moment aligned in the ab plane. The ordered magnetic moments are determined as 9.4(2) mu B, 6.6(2) mu B, 6.4(2) mu B, and 6.1(2) mu B for R = Tb, Dy, Ho, and Er, respectively. A comparison of the low-temperature magnetic structures for both the extensively investigated topological kagome metal series of RV6Sn6 and RMn6Sn6 is given in detail. This allows to gain new insights into the complex magnetic interactions, diverse single-ion magnetic anisotropies and spin dynamics in these compounds. The reported ground-state magnetic structures in RV6Sn6 (R = Tb, Dy, Ho, Er) can pave the way for further explorations of the possible interplay between magnetism and topologically nontrivial electron band structures in the magnetically ordered phase regime.

The spin-orbit assisted Mott insulator α-RuCl3 is a prime candidate for material realization of the Kitaev quantum spin liquid. While little attention has been paid to charge degrees of freedom, charge effects, such as electric polarization, may arise in this system. Here, we report distortion-induced local electric polarization in α-RuCl3 as evidenced by single-crystal X-ray diffraction, second harmonic generation (SHG) and dielectric measurements. The SHG signal appears at room temperature and develops substantially in the Kitaev paramagnetic state when short-range spin correlations come into play. Despite sizable pyroelectric currents in the Kitaev paramagnetic state, the absence of hysteresis in the polarization-electric field (P-E) points to the short-range nature of electric polarization. This localized electric polarization is likely the result of distortion-induced charge dimerization, achieved through virtual hopping-induced charge redistribution. In addition, the electric polarization is boosted by short-range spin correlations via spin-phonon coupling in the Kitaev paramagnetic state. Our results emphasize the importance of charge degrees of freedom in α-RuCl3, which establish a novel platform to investigate charge effects in Kitaev materials.

A quantum spin liquid (QSL) arises from a highly entangled superposition of many degenerate classical ground states in a frustrated magnet, and is characterized by emergent gauge fields and deconfined fractionalized excitations (spinons). Because such a novel phase of matter is relevant to high-transition-temperature superconductivity and quantum computation, the microscopic understanding of QSL states is a long-sought goal in condensed matter physics. The 3D pyrochlore lattice of corner-sharing tetrahedra can host a QSL with U(1) gauge fields called quantum spin ice (QSI), which is a quantum (with effective S=1/2) analog of the classical (with large effective moment) spin ice. A key difference between QSI and classical spin ice is the predicted presence of the linearly dispersing collective excitations near zero energy, dubbed the "photons", arising from emergent quantum electrodynamics, in addition to the spinons at higher energies. Recently, 3D pyrochlore systems Ce2M2O7 (M = Sn, Zr, Hf) have been suggested as effective S=1/2 QSI candidates, but there has been no evidence of quasielastic magnetic scattering signals from photons, a key signature for a QSI. Here, we use polarized neutron scattering experiments on single crystals of Ce2Zr2O7 to conclusively demonstrate the presence of magnetic excitations near zero energy at 50 mK in addition to signatures of spinons at higher energies. By comparing the energy (E), wave vector (Q), and polarization dependence of the magnetic excitations with theoretical calculations, we conclude that Ce2Zr2O7 is the first example of a dipolar-octupolar π flux QSI with dominant dipolar Ising interactions, therefore identifying a microscopic Hamiltonian responsible for a QSL.

The magnetic properties of spinel nanoparticles can be controlled by synthesizing particles of a specific shape and size. The synthesized nanorods, nanodots and cubic nanoparticles have different crystal planes selectively exposed on the surface. The surface effects on the static magnetic properties are well documented, while their influence on spin waves dispersion is still being debated. Our ability to manipulate spin waves using surface and defect engineering in magnetic nanoparticles is the key to designing magnonic devices. We synthesized cubic and spherical nanoparticles of a classical antiferromagnetic material Co3O4 to study the shape and size effects on their static and dynamic magnetic proprieties. Using a combination of experimental methods, we probed the magnetic and crystal structures of our samples and directly measured spin wave dispersions using inelastic neutron scattering. We found a weak, but unquestionable, increase in exchange interactions for the cubic nanoparticles as compared to spherical nanoparticle and bulk powder reference samples. Interestingly, the exchange interactions in spherical nanoparticles have bulk-like properties, despite a ferromagnetic contribution from canted surface spins.