We performed high-precision magnetization measurements up to 120 T on three compositions of the newly discovered kagome antiferromagnet YCu_3(OD)_7-xBr_2+x (YCOB), revealing a previously unobserved 5/9 fractional magnetization plateau. All YCOB samples with different Br^- concentrations exhibit nearly identical magnetization curves below 60 T, whereas the 5/9 plateau appears at markedly different fields in the ultrahigh-field regime. By modeling the experimental data using tensor-network calculations, we derive the effective spin Hamiltonians for the YCOB family with three spatially anisotropic Heisenberg couplings (the 3J-type model), which quantitatively reproduces the measured magnetization processes and captures the composition-dependent evolution of the 5/9 plateau. Furthermore, our theoretical analysis suggests the emergence of a spin supersolid phase in the field window between the 1/3 and 5/9 plateaus, which is sensitive to spin exchange parameters and accounts for the significant variation in the critical fields of the 5/9 plateau observed among different YCOB compositions.

Spin-1 kagome lattice antiferromagnets provide a versatile platform for exploring exotic quantum states, such as classical spin liquids and spin nematics, owing to the confluence of geometric frustration, bilinear and biquadratic interactions, and single-ion anisotropy. Here, we investigate the ground state and spin dynamics of a nearly perfect s = 1 kagome lattice, $${({\text{CH}}_{3}{\text{NH}}_{3})}_{2}{\text{NaV}}_{3}{\text{F}}_{12}$$, which hosts dominant antiferromagnetic interactions (J ≈ 10 K) alongside easy-axis anisotropy. Using a combination of thermodynamic and resonance techniques, we identify the occurrence of weak ferromagnetic ordering at TC ≈ 4 K. Singularly, even in this time-reversal symmetry-breaking state, muon spin relaxation, 23Na spin-lattice relaxation rate, and magnetic specific heat measurements collectively reveal persistent spin dynamics and intriguing gapless excitations. The observation of liquid-like correlations in the ground state establishes $${({\text{CH}}_{3}{\text{NH}}_{3})}_{2}{\text{NaV}}_{3}{\text{F}}_{12}$$ as a rare instance of the coexistence of dynamically fluctuating spins and weak ferromagnetism, raising the possibility of realizing an intriguing ground state in s = 1 kagome antiferromagnets with Ising anisotropy.

We present magnetic-field-dependent evolution of magnetization and spin dynamics in the quasi-two-dimensional spin-1/2 magnet Cu_2(OH)_3Br, consisting of alternately coupled ferromagnetic Cu1 and antiferromagnetic Cu2 spin chains. Terahertz spectroscopy reveals a pronounced field-direction dependence of the low-energy magnetic excitation spectrum. For magnetic fields applied perpendicular to the spin chains, B∥ a and B∥ c^*, the spectra undergo abrupt reconstructions at the spin-flop transitions identified independently by high-field magnetization measurements. For B∥ b, by contrast, no spin-flop occurs; instead, the excitation spectrum evolves continuously with field and exhibits a strong terahertz radiation polarization dependence as the ferromagnetic Cu1 subsystem becomes progressively polarized. At higher fields, the complex low-field spectrum is replaced by a reduced set of broad excitations, consistent with a weakening of the coupling between the ferromagnetic and antiferromagnetic chain subsystems. Complementary Raman spectroscopy resolves magnon and spinon excitations alongside several phonon modes and traces the characteristic temperature- and magnetic-field-dependent evolution of the magnetic excitations. The combined spectroscopic and magnetization results map out how a magnetic field reorganizes the coupled ferromagnetic and antiferromagnetic subsystems in Cu_2(OH)_3Br across field-induced phase transitions.

Na2Co2TeO6 is a primary 3d Kitaev magnet characterized by strong electronic correlations; however, its properties are not fully understood. In this study, we present a revised nuclear structure based on single-crystal neutron diffraction at ambient conditions, along with spin dynamics under magnetic fields investigated via muon spin relaxation and rotation and inelastic neutron scattering. Structural analysis resolves inconsistencies in the Na-ion ordering by revealing a triangular Na layer between the Co-based honeycomb planes. Transverse-field muon experiments confirm a quantum phase transition induced by a magnetic field at 5.7 T to a quantum-disordered state. Inelastic neutron scattering at 8.55 T applied along the a axis reveals dichotomous magnetic excitations between low-energy magnons coexisting with high-energy spinons. These findings indicate the emergence of a spin liquid-like state within a partially polarized background, highlighting the potential of this system for exploring field-induced quantum phenomena associated with Kitaev magnetism.

Chiral magneto-phononic modes-hybridized vibrational states that carry angular momentum through coupling with magnetic degrees of freedom-offer a novel route for controlling magnetism and enabling topological phononics. Here, we report the magnetic switching of these hybridized chiral phonons, ZnxFe2-xMo3O8, using helicity-resolved magneto-Raman spectroscopy. By tuning the Zn concentration across antiferromagnetic and ferrimagnetic regimes, we uncover two key phenomena: (i) a giant, spontaneous zero-field splitting (similar to 10 cm-1) of the doubly degenerate E 2 hybridized phonon modes in the ferrimagnetic state, and (ii) a field-induced Zeeman effect in the antiferromagnetic and paramagnetic phases. The phonon splitting in the ferrimagnetic phase exhibits a pronounced asymmetry with respect to the applied field direction and shows a strong correlation with magnetization, highlighting a selective phonon-magnon coupling and the emergence of large effective magnetic moments driven by magnetization. Our results demonstrate that chiral hybridized phonons can be dynamically controlled through their intrinsic entanglement with magnon and spin degrees of freedom, enabling the tuning of effective magnetic moments via magnetization and external magnetic fields. These findings establish ZnxFe2-xMo3O8 as a compelling platform for exploring novel magneto-phononic phenomena.

The honeycomb cobaltate Na_2Co_2TeO_6 has recently been proposed as a candidate material for hosting field-induced quantum spin liquid (QSL) behavior. Here, we present a comprehensive thermodynamic study of its low-temperature, high-field phase diagram using magnetization, specific heat, and magnetocaloric-effect measurements down to 1 K. In zero field, we observe a weak residual moment that provides further insight into the nature of the magnetic ground state. For in-plane magnetic fields (B ∥ a^*), we identify three field-induced transitions at B_c1≃ 6 T, B_c2≃ 7.8 T, and B_c3≃ 10.4 T. The magnetic Grüneisen parameter and specific heat reveal clear thermodynamic signatures of these successive phase transitions enclosing two intermediate phases. Contrary to expectations for a field-induced QSL, the phase between B_c2 and B_c3 lacks enhanced magnetic entropy but instead shows behavior consistent with a distinct ordered state. Above B_c3, the absence of additional anomalies indicates a crossover to a conventional spin-polarized regime. Our results place stringent thermodynamic constraints on the proposed QSL scenario in Na_2Co_2TeO_6, calling for further microscopic investigations to establish the precise nature of the field-induced phases.

Competing magnetic interactions and frustration-induced quantum fluctuations in spatially anisotropic low-dimensional magnets often give rise to exotic magnetic phenomena, including field-induced phases. Here, we present crystal structure, magnetic susceptibility, specific heat, and electron spin resonance (ESR) measurements on polycrystalline Y2CuGe4O12, supported by density functional theory (DFT) calculations. In this compound, the Cu^2+ ions form a distorted triangular lattice with competing intraplanar ferromagnetic (J_1 ≈ 0.138 K and J_2 ≈ 0.01 K) and antiferromagnetic (J_3 ≈ -3.22 K) exchange interactions, together with a weaker interplanar antiferromagnetic coupling (J_4 ≈ -1.56 K). These interactions account for the small Curie–Weiss temperature, θ CW=-1.8 K. Despite the dominant antiferromagnetic interactions, no signature of long-range magnetic ordering is observed down to 0.4 K. Instead, broad maxima in both the magnetic susceptibility and magnetic specific heat reveal the development of short-range spin correlations, further supported by the critical ESR linewidth broadening characteristic of low-dimensional frustrated magnets. Application of an external magnetic field progressively suppresses the broad maximum in the magnetic specific heat, reflecting competition between the Zeeman and exchange energy scales, and drives the system into a field-polarized state above the saturation field, μ_0H_ s=2.6 T. In this regime, the magnetic specific heat exhibits an exponential temperature dependence, consistent with gapped magnon excitations. These results establish Y_2CuGe4O12 as a rare distorted triangular-lattice magnet in which further-neighbor exchange interactions dominate the magnetic behavior, providing a promising platform for exploring frustration-driven quantum phenomena.

The excitonic insulator candidate Ta_{2}Pd_{3}Te_{5} has emerged as a promising platform to explore macroscopic quantum condensation and its collective excitations. Using polarization-resolved Raman spectroscopy, we identify a symmetry-selective electronic mode that softens and undergoes linewidth renormalization across the characteristic temperature T^{*}∼100K. This mode, most prominent in the B_{3g} channel, is assigned to vestigial collective excitations associated with excitonic correlations, as evidenced by its order-parameter-like temperature evolution and symmetry dependence. In parallel, a damped Drude-like response exhibits a suppressed scattering rate and maximum intensity at T^{*}, while phonon intensities display symmetry-dependent anomalies, signaling anisotropic band reconstructions and the spontaneous opening of a collective condensation gap. These observations provide compelling spectroscopic evidence for collective amplitude excitations in Ta_{2}Pd_{3}Te_{5}, establishing this material as a bulk excitonic insulator.

We develop a gauge-invariant theory of higher-order magnon quantum geometry probed by two-magnon Raman circular dichroism (RCD). The Raman operator decomposes into Berry connections, covariant derivatives, and products of Berry connections, giving rise to quantum geometric tensors beyond the quantum metric and Berry curvature. Applying this theory to a field-polarized Kitaev magnet, we show that higher-order geometric tensors govern the dichroic response. Our results establish RCD as a spectroscopic probe of generalized magnon quantum geometry.

ABSTRACT Chiral magneto‐phononic modes—hybridized vibrational states that carry angular momentum through coupling with magnetic degrees of freedom—offer a novel route for controlling magnetism and enabling topological phononics. Here, we report the magnetic switching of these hybridized chiral phonons, Zn x Fe 2‐ x Mo 3 O 8 , using helicity‐resolved magneto‐Raman spectroscopy. By tuning the Zn concentration across antiferromagnetic and ferrimagnetic regimes, we uncover two key phenomena: (i) a giant, spontaneous zero‐field splitting (∼10 cm −1 ) of the doubly degenerate E 2 hybridized phonon modes in the ferrimagnetic state, and (ii) a field‐induced Zeeman effect in the antiferromagnetic and paramagnetic phases. The phonon splitting in the ferrimagnetic phase exhibits a pronounced asymmetry with respect to the applied field direction and shows a strong correlation with magnetization, highlighting a selective phonon‐magnon coupling and the emergence of large effective magnetic moments driven by magnetization. Our results demonstrate that chiral hybridized phonons can be dynamically controlled through their intrinsic entanglement with magnon and spin degrees of freedom, enabling the tuning of effective magnetic moments via magnetization and external magnetic fields. These findings establish Zn x Fe 2‐ x Mo 3 O 8 as a compelling platform for exploring novel magneto‐phononic phenomena.

Competing exchange interactions in frustrated three-dimensional spin lattices offer a promising route to realize rich physical phenomena, including spin liquids with exotic low-energy excitations. In this work, we focus on the three-dimensional frustrated magnet MgCrGaO4, where Cr3+ ions occupy a pyrochlore-like network. Due to intrinsic disorder and partial occupation of the pyrochlore sites by magnetic ions, the actual structure highlights the famous closed loops of the pyrochlore lattice. Our thermodynamic, electron spin resonance (ESR), muon spin relaxation (& micro;SR), and inelastic neutron scattering (INS) techniques detect no signature of magnetic order or spin freezing down to 57 mK, despite a sizable exchange interaction (J = 58 K) between Cr3+ moments. Below the characteristic exchange energy scale, all probes reveal the emergence of antiferromagnetic short-range spin correlations, corroborated by magnetic diffuse scattering in the wave vector dependence of low-energy magnetic excitations centered on Q = 1.5 & Aring;-1 in inelastic neutron scattering experiments. The low-temperature specific heat follows a near-quadratic dependence suggesting the presence of nontrivial low-energy excitations. These results establish MgCrGaO4 as a rare three-dimensional spin liquid with exotic excitations, offering a strong impetus for the experimental realization of spin liquids in higher-dimensional frustrated quantum magnets.

Star lattice, which can be visualized as a honeycomb network with each vertex replaced by a triangle, provides a rare platform for realizing exotic quantum states such as quantum spin liquids and disorder-driven random-singlet (RS) states. Herein, we investigate the ground-state properties of the three-dimensional (3D) stuffed hyper-star lattice Li_2Cu_2(MoO_4)_3, which exhibits a crossover from short-range spin correlations to a disorder-driven RS-like state below T^*∼15.8 K. Thermodynamic and microscopic measurements capture this crossover through a change in the power-law behavior of various observables, from ∼ T^0.25 for T > T^* to ∼ T^-0.50 for T < T^*. Upon further cooling, a quasi-frozen state emerges near T_ f = 0.32 K, likely associated with weakly coupled spin chains within the hyper-star spin network. Our results underscore the crucial role of orphan spins and weak residual interactions in stabilizing a disorder-driven quantum-disordered state in 3D.

Trillium lattices, where magnetic ions form a chiral network of corner-sharing triangles, offer a three-dimensional magnetic framework that can host fragile classical spin-liquid states. Herein, we report on the magnetization, specific heat, electron spin resonance (ESR), and muon spin relaxation (μSR) of K_2Fe_2(MoO_4)(PO_4)_2 single crystals. Magnetization measurements reveal strong antiferromagnetic interactions coexisting with weak magnetic order at T_ N = 5.2 K, as evidenced by a λ-like anomaly observed in the magnetic susceptibility, a critical enhancement of the muon spin relaxation rate and the wipeout of the ESR signal as the temperature approaches T_ N. Above T_ N, two distinct developments of short-range spin correlations are identified at T_ H = 34 K and T_ L = 10 K, supported by magnetic specific heat anomalies and the temperature dependence of the ESR linewidth and g-factor. Upon cooling below T_ N, an anomaly appears at T^* = 3.2 K in thermodynamic observables and the muon spin relaxation rate, indicative of spin reorientation driven by residual interactions. Despite the presence of magnetic order, μSR experiments reveal dynamically fluctuating spins persisting even in the ordered state. Moreover, the suppression of T_ N under applied magnetic fields (μ_0H ≥ 2 T) suggests that K_2Fe_2(MoO_4)(PO_4)_2 constitutes a promising candidate for exploring field-induced spin-liquid behavior in three-dimensionally coupled trillium lattices.

Magnetic compounds with noncentrosymmetric chiral crystal structures and spin-frustrated lattices often exhibit complex magnetic ordering and coupled responses. In this report, we present a comprehensive study of the chiral and triangular lattice magnetic system Ni2ScSbO6, which exhibits an incommensurate noncollinear helical antiferromagnetic long-range ordering at a temperature of TN = 62 K, as revealed by bulk magnetization, specific heat, and neutron diffraction studies. The onset of this magnetic ordering is closely linked to a series of strongly coupled phenomena occurring at TN. A clear dielectric anomaly in the form of a sharp )-like peak is observed at TN, triggered by an isostructural distortion, which is mediated by the magnetostriction effect in this system, as evidenced by our synchrotron x-ray diffraction studies. Moreover, a clear anomalous phonon softening for various Raman modes is observed at TN, which can be attributed to substantial spin-phonon coupling combined with the influence of magnetostriction effects. All these strongly correlated phenomena, occurring concurrently with the emergence of the helical antiferromagnetic order, demonstrate an entangled behavior of various microscopic degrees of freedom in this system, thus highlighting Ni2ScSbO6 as a unique material.

Altermagnets constitute an emerging class of magnetic materials that combine compensated antiferromagnetic order with spin-split excitations arising from crystalline symmetries. Despite strong theoretical interest, their experimental identification remains challenging. Here, we demonstrate that helicity- and angle-resolved Raman scattering measurements reveal reduced rotational symmetries of magnons and a pronounced imbalance between left- and right-circular polarization channels, indicating momentum-dependent magnon handedness. First-principles DFT+ U $U$ calculations combined with linear spin-wave theory uncover a characteristic plaid-like spin-splitting structure in momentum space. The resulting magnon spin textures are dictated by the unconventional sublattice symmetries of MnTe 2 $\text{MnTe}_2$ and closely emulate those of altermagnetic electronic bands. Our work provides evidence of chiral spin-wave excitations unique to this non-coplanar antiferromagnet.

We present a comprehensive investigation of the effects of Fe doping on the lattice dynamics, magnetic ordering, and magneto-transport properties of the intercalated van der Waals antiferromagnets Co1-xFexNb3S6 (x = 0.1 and 0.3). Temperature- and polarization-dependent Raman scattering measurements reveal a pronounced blue shift of the 180 cm-1 phonon mode with increasing Fe concentration, indicating enhanced sensitivity of lattice vibrations to Fe-induced structural and mass effects. While the temperature evolution of the phonon modes is dominated by conventional anharmonic phonon softening, subtle anomalies observed near the Néel temperature for x = 0.1 point to weak spin-phonon coupling. Electrical transport and magnetic susceptibility data show clear signatures of the antiferromagnetic phase transitions at TN 20.5-23.7 K for x = 0.1 and TN 32.0 K for x = 0.3. Out-of-plane magnetization measurements reveal hysteretic behavior with two field-induced transitions for x =0.1, which evolve into a single hysteresis loop at x =0.3, signaling a subtle reconstruction of the magnetic ground state. Magneto-transport measurements for x = 0.1 further display a butterfly-shaped hysteretic magnetoresistance and a weak topological Hall effect; however, both features are strongly suppressed at x = 0.3. These results illustrate the critical role of Fe-induced magnetic structure reconstruction in fine-tuning topological and magnetic transport phenomena in intercalated van der Waals antiferromagnets.

The subtle interplay between competing degrees of freedom, crystal electric fields, and spin correlations can lead to exotic quantum states in 4 f ion-based frustrated triangular lattice antiferromagnets. We present the crystal structure, thermodynamic and muon spin relaxation (mu SR) studies of the 4 f ion-based frustrated magnet Ba4YbReWO12, wherein Yb3+ ions constitute a triangular lattice. The magnetic susceptibility does not show any signature of spin freezing down to 1.9 K or long-range magnetic ordering down to 0.4 K. The low-temperature Curie-Weiss fit to the inverse magnetic susceptibility data reveals a weak antiferromagnetic exchange interaction, which is corroborated by the fit of magnetic specific heat data following the J1 - J2 model with the nearest-neighbor-exchange interaction of J1 approximate to -0.197 K between the Jeff = 1/2 states of the Yb3+ moments in the lowest Kramers doublet. The lowest Kramers ground state doublet is well separated from the first excited state with a gap of Delta CEF = 278 K, as evidenced by our mu SR experiments that support the realization of Jeff = 1/2 at low temperatures. The specific heat experiments do not detect a phase transition down to 56 mK. The magnetic specific heat shows a broad maximum at 90 mK suggesting a disordered ground state with short-range spin correlations. The associated magnetic entropy release at low temperatures is consistent with that expected for the Jeff = 1/2 state. The zero-field mu SR measurements show neither the signature of spin freezing nor a phase transition, at least down to 43 mK. Our results suggest a dynamic, disordered ground state in this Jeff = 1/2 frustrated triangular lattice antiferromagnet. Ba4RReWO12 (R=rare earth) offers a viable platform to realize intriguing quantum states borne out of spin-orbit coupling and frustration.

We report a comprehensive investigation of the structural and magnetic properties of Na_5Yb(MoO_4)_4, a member of the stretched diamond magnetic lattice family. Neutron powder diffraction at 3.3 K confirms that the compound crystallizes in the tetragonal I4_1/a space group, with a large interatomic separation of 6.33 Å between magnetic Yb ions forming a three-dimensional stretched diamond framework. Magnetic susceptibility and specific heat measurements reveal no evidence of long-range magnetic order down to 60 mK. The low-temperature magnetic behavior is governed by an effective J_eff = 1/2 Kramers doublet ground state, well separated from excited crystal-field levels, arising from the distorted dodecahedral oxygen coordination of Yb^3+. Density functional theory calculations within the DFT+U framework indicate that exchange interactions between Yb ions are negligibly small, consistent with the long O–Mo–O super-superexchange pathways. The temperature dependence of the specific heat exhibits signatures of gapped spin excitations, most likely originating from long-range dipolar correlations and further shaped by weak exchange interactions together with the strong single-ion anisotropy of the Yb moments. Muon spin relaxation measurements reveal persistent low-energy spin dynamics, indicating that dipolar correlations remain dynamic and are insufficient to stabilize static magnetic order down to 50 mK. These results identify Na_5Yb(MoO_4)_4 as a rare example of a dipolar quantum paramagnet in which single-ion physics and long-range dipolar interactions dominate, while exchange interactions are suppressed to the millikelvin energy scale.

The star lattice, which can be visualized as a honeycomb network with each vertex replaced by a triangle, provides a rare platform for realizing exotic quantum states such as quantum spin liquids and disorder-driven random-singlet (RS) states. Herein, we investigate the ground-state properties of the three-dimensional (3D) stuffed hyper-star lattice Li2Cu2(MoO4)(3), which exhibits a crossover from short-range spin correlations to a disorder-driven RS-like state below T-& lowast;similar to 15.8 K. Thermodynamic and microscopic measurements capture this crossover through a change in the power-law behavior of various observables, from similar to T- 0.25 for T > T-& lowast; to similar to T-0.50 for T < T-& lowast;. Upon further cooling, a quasifrozen state emerges near T-f = 0.32 K, likely associated with weakly coupled spin chains within the hyper-star spin network. Our results underscore the crucial role of orphan spins and weak residual interactions in stabilizing a disorder-driven quantum-disordered state in three dimensions.