In Volborthite, spin-1/2 moments form a distorted Kagomé lattice, of corner sharing isosceles triangles with exchange constants $J$ on two bonds and $J'$ on the third bond. We study the properties of such spin systems, and show that despite the distortion, the lattice retains a great deal of frustration. Although sub-extensive, the classical ground state degeneracy remains very large, growing exponentially with the system perimeter. We consider degeneracy lifting by thermal and quantum fluctuations. To linear (spin wave) order, the degeneracy is found to stay intact. Two complementary approaches are therefore introduced, appropriate to low and high temperatures, which point to the same ordered pattern. In the low temperature limit, an effective chirality Hamiltonian is derived from non-linear spin waves which predicts a transition on increasing $J'/J$, from $\sqrt 3\times \sqrt 3$ type order to a new ferrimagnetic {\em striped chirality} order with a doubled unit cell. This is confirmed by a large-N approximation on the O($n$) model on this lattice. While the saddle point solution produces a line degeneracy, $O(1/n)$ corrections select the non-trivial wavevector of the striped chirality state. The quantum limit of spin 1/2 on this lattice is studied via exact small system diagonalization and compare well with experimental results at intermediate temperatures. We suggest that the very low temperature spin frozen state seen in NMR experiments may be related to the disconnected nature of classical ground states on this lattice, which leads to a prediction for NMR line shapes.
A novel cuprate Volborthite, Cu3V2O7(OH)2-2H2O, containing an S-1/2 (Cu 2+ spin) kagome-like lattice is studied by magnetic susceptibility, specific heat, and 51 V NMR measurements. Signs for neither long-range order nor spin-gapped singlet ground states are detected down to 1.8 K, in spite of large antiferromagnetic couplings of ~100 K between Cu spins forming a two-dimensional kagome-like network. It is suggested that Volborthite represents a system close to a quantum critical point between classical long-range ordered and quantum disordered phases.
Two kagome compounds, volborthite Cu3V2O7(OH)2-2H2O and herbertsmithite ZnCu3(OH)6Cl2, are compared in order to derive information about the intrinsic properties of the spin-1/2 kagome antiferromagnet. Volborthite shows a broad maximum at T ~ J / 4 and the approach at T = 0 to a large finite value of the bulk magnetic susceptibility chi_bulk as well as the local susceptibility chi_local from NMR measurements. These must be intrinsic properties for the spin-1/2 kagome antiferromagnet, as similar behavior has also been reported in chi_local for herbertsmithite [Olariu A et al. 2008 Phys. Rev. Le…
The magnetization of two spin-1/2 kagome antiferromagnets, volborthite and vesignieite, has been measured in pulsed magnetic fields up to 68 T. A magnetization plateau is observed for each compound near the highest magnetic field. Magnetizations at saturation are approximately equal to 0.40Ms for both compounds, where Ms is the fully saturated magnetization, irrespective of a difference in the distortion of the kagome lattice between the two compounds. It should be noted that these values of magnetizations are significantly larger than Ms/3 predicted theoretically for the one-third magnetizati…
In this Letter, we identify a noncoplanar chiral spin texture on the distorted kagomé-lattice antiferromagnets induced by the presence of a magnetic field applied perpendicular to the distorted kagomé plane. The noncoplanar chiral spin texture has a nonzero scalar spin chirality similar to a chiral quantum spin liquid with broken time-reversal symmetry. In the noncoplanar regime we observe nontrivial topological magnetic excitations and thermal Hall response through the emergent field-induced scalar spin chirality in contrast to collinear ferromagnets in which the Dzyaloshinskii-Moriya (DM) sp…
Thermodynamic investigations on volborthite (Cu3V2O7(OH)2 2H2O), which possesses a two-dimensional kagome structure of S-1/2 spins, are presented. The low-temperature heat capacities of volborthite and its Zn analogue compound were measured by the relaxation calorimetry technique between 0.8 and 45 K. The magnetic heat capacity of volborthite is characterized by two contributions of T-linear and T2 dependences, the former of which is large above 1 K, giving evidence of dense gapless excitations. We find a distinct kink in Cp T-1 at T* = 1 K, which demonstrates a thermodynamic phase transition …
We report 51V-NMR study on a high-quality powder sample of volborthite Cu3V2O7(OH)2/2H2O, a spin-1/2 Heisenberg antiferromagnet on a distorted kagome lattice formed by isosceles triangles. In the magnetic fields below 4.5 T, a sharp peak in the nuclear spin-lattice relaxation rate 1/T1 accompanied with line broadening revealed a magnetic transition near 1 K. The low temperature phase shows anomalies such as a Lorentzian line shape, a 1/T1 propto T behavior indicating dense low energy excitations, and a large spin-echo decay rate 1/T2 pointing to unusually slow fluctuations. Another magnetic ph…
Magnetic properties of the spin-1/2 kagome-like compound volborthite are studied using a high-quality polycrystalline sample. It is evidenced from magnetization and specific heat measurements that the spins on the kagome lattice still fluctuate at low temperature, down to T = 60 mK that corresponds to 1/1500 of the nearest-neighbor antiferromagnetic interaction, exhibiting neither a conventional long-range order nor a spin gap. In contrast, 51V NMR experiments revealed a sharp peak at 1 K in relaxation rate, which indicates that a certain exotic order occurs. Surprisingly, we have observed thr…
Volborthite compound is one of the very few realizations of S=1/2 quantum spins on a highly frustrated kagome-like lattice. Low-T SQUID measurements reveal a broad magnetic transition below 2K which is further confirmed by a peak in the 51V nuclear spin relaxation rate (1/T1) at 1.4K$\pm$0.2K. Through 51V NMR, the ground state (GS) appears to be a mixture of different spin configurations, among which 20% correspond to a well defined short range order, possibly of the $\sqrt{3} \times \sqrt{3}$ type. While the freezing involve all the Cu$^{2+}$ spins, only 40% of the copper moment is actually f…
We present spatial and dynamic information on the s=1/2 distorted kagome antiferromagnet volborthite, Cu3V2O7(OD)2.2D2O, obtained by polarized and inelastic neutron scattering. The instantaneous structure factor, S(Q), is dominated by nearest neighbor pair correlations, with short range order at wave vectors Q1=0.65(3) Å^-1 and Q2=1.15(5) Å^-1 emerging below 5 K. The excitation spectrum, S(Q,ω), reveals two steep branches dispersing from Q1 and Q2, and a flat mode at ω=5.0(2) meV. The results allow us to identify the cross-over at T*=1 K in 51V NMR and specific heat measurements as the build-u…
Thermodynamic properties such as magnetic susceptibility and specific heat have been computed for the Heisenberg Antiferromagnet with spatially anisotropic exchange on the kagome lattice on clusters up to N=24 spins from the full spectra obtained by exact diagonalization. This approach is shown to provide a good represention of these thermodynamic properties above temperatures of about $J_{\rm av}/5$ where $J_{\rm av}$ is an average of the coupling constants. Comparison with experimental Volborthite data obtained by Hiroi {\it {et al}} [J. Phys. Soc. Jpn. {\bf 70},3377 (2001)] shows that Volbo…
The Kagome-lattice-based material, Volborthite, $\mathrm{Cu_3 V_2 O_7 (OH)_2 \cdot 2 H_2 O}$, has been considered as a promising platform for discovery of unusual quantum ground states due to the frustrated nature of spin interactions. Here we explore possible quantum spin liquid and magnetically ordered phases in a two-dimensional non-symmorphic lattice described by $p2gg$ layer space group, which is consistent with the spatial anisotropy of the spin model derived from density functional theory (DFT) for Volborthite. Using the projective symmetry group (PSG) analysis and Schwinger boson mean …
Microscopic spin interactions on a deformed Kagomé lattice of volborthite are investigated through magnetoelastic couplings. A negative longitudinal magnetostriction $ΔL<0$ in the $b$ axis is observed, which depends on the magnetization $M$ with a peculiar relation of $ΔL/L \propto M^{1.3}$. Based on the exchange striction model, it is argued that the negative magnetostriction originates from a pantograph-like lattice change of the Cu-O-Cu chain in the $b$ axis, and that the peculiar dependence arises from the local spin correlation. This idea is supported by DFT+$U$ calculations simulating th…
We determined the spin exchanges between the Cu2+ ions in the kagome layers of volborthite, Cu3V2O7(OH)2x2H2O, by performing the energy-mapping analysis based on DFT+U calculations, to find that the kagomé layers of Cu2+ ions are hardly spin-frustrated, and the magnetic properties of volborthite below ~75 K should be described by very weakly interacting antiferromagnetic uniform chains made up of effective S=1/2 pseudospin units. This conclusion was verified by synthesizing single crystals of not only Cu3V2O7(OH)2x2H2O but also its deuterated analogue Cu3V2O7(OD)2x2D2O and then by investigatin…
When quantum fluctuations destroy underlying long-range ordered states, novel quantum states emerge. Spin-liquid (SL) states of frustrated quantum antiferromagnets, in which highly-correlated spins keep to fluctuate down to very low temperatures, are prominent examples of such quantum states. SL states often exhibit exotic physical properties, but the precise nature of the elementary excitations behind such phenomena remains entirely elusive. Here we utilize thermal Hall measurements that can capture the unexplored property of the elementary excitations in SL states, and report on the observat…
Recently, thermal Hall effect has been observed in the paramagnetic state of Volborthite, which consists of distorted Kagome layers with $S=1/2$ local moments. Despite the appearance of a magnetic order below $1 \, \mathrm{K}$, the response to external magnetic field and unusual properties of the paramagnetic state above $1 \, \mathrm{K}$ suggest possible realization of exotic quantum phases. Motivated by these discoveries, we investigate possible spin liquid phases with fermionic spinon excitations in a non-symmorphic version of the Kagome lattice, which belongs to the two-dimensional crystal…
We report results of 51V NMR in the field-induced phase of volborthite Cu3V2O7(OH)dot2H2O, a spin-1/2 antiferromagnet on a distorted kagome lattice. In magnetic fields above 4.5 T, two types of V sites with different spin-echo decay rates are observed. The hyperfine field at the fast decaying sites has a distribution, while it is more homogeneous at the slowly decaying sites. Our results indicate a heterogeneous state consisting of two spatially alternating Cu spin systems, one of which exhibits anomalous spin fluctuations contrasting with the other showing a conventional static order.
Motivated by a recent experiment on volborthite, a typical spin-$1/2$ antiferromagnet with a kagomé lattice structure, we study the magnetization process of a classical Heisenberg model on a spatially distorted kagomé lattice using the Monte Carlo (MC) method. We find a distortion-induced magnetization step at low temperatures and low magnetic fields. The magnitude of this step is given by $Δm_z=\left|1-α\right|/3α$ at zero temperature, where $α$ denotes the spatial anisotropy in exchange constants. The magnetization step signals a first-order transition at low temperatures, between two phases…
We study the properties of the Heisenberg antiferromagnet with spatially anisotropic nearest-neighbour exchange couplings on the kagome net, i.e. with coupling J in one lattice direction and couplings J' along the other two directions. For J/J' > 1, this model is believed to describe the magnetic properties of the mineral volborthite. In the classical limit, it exhibits two kinds of ground states: a ferrimagnetic state for J/J' < 1/2 and a large manifold of canted spin states for J/J' > 1/2. To include quantum effects self-consistently, we investigate the Sp(N) symmetric generalisation of the …
We have synthesized high-quality single crystals of volborthite, a seemingly distorted kagome antiferromagnet, and carried out high-field magnetization measurements up to 74 T and 51V NMR measurements up to 30 T. An extremely wide 1/3 magnetization plateau appears above 28 T and continues over 74 T at 1.4 K, which has not been observed in previous study using polycrystalline samples. NMR spectra reveal an incommensurate order (most likely a spin-density wave order) below 22 T and a simple spin structure in the plateau phase. Moreover, a novel intermediate phase is found between 23 and 26 T, wh…
Volborthite offers an interesting example of a highly frustrated quantum magnet in which ferromagnetic and antiferromagnetic interactions compete on anisotropic kagome lattices. A recent density functional theory calculation has provided a magnetic model based on coupled trimers, which is consistent with a broad 1/3-magnetization plateau observed experimentally. Here we study the effects of Dzyaloshinskii-Moriya (DM) interactions in volborthite. We derive an effective model in which pseudospin-1/2 moments emerging on trimers form a network of an anisotropic triangular lattice. Using the effect…
We present a microscopic magnetic model for the spin-liquid candidate volborthite Cu3V2O7(OH)2(H2O)2. The essentials of this DFT-based model are (i) the orbital ordering of Cu(1) 3d 3z2-r2 and Cu(2) 3d 3x2-y2, (ii) three relevant couplings J_ic, J_1 and J_2, (iii) the ferromagnetic nature of J_1 and (iv) frustration governed by the next-nearest-neighbor exchange interaction J_2. Our model implies magnetism of frustrated coupled chains in contrast to the previously proposed anisotropic kagome model. Exact diagonalization studies reveal agreement with experiments.
In the search for spin-1/2 kagome antiferromagnets, the mineral volborthite has recently been the subject of experimental studies [Hiroi et al.,2001]. It has been suggested that the magnetic properties of this material are described by a spin-1/2 Heisenberg model on the kagome lattice with spatially anisotropic exchange couplings. We report on investigations of the Sp(N) symmetric generalisation of this model in the large N limit. We obtain a detailed description of the dependence of possible ground states on the anisotropy and on the spin length S. A fairly rich phase diagram with a ferrimagn…
We study the Heisenberg model on the pinwheel distorted kagome lattice as observed in the material Rb_2Cu_3SnF_12. Experimentally relevant thermodynamic properties at finite temperatures are computed utilizing numerical linked-cluster expansions. We also develop a Lanczos-based, zero-temperature, numerical linked cluster expansion to study the approach of the pinwheel distorted lattice to the uniform kagome-lattice Heisenberg model. We find strong evidence for a phase transition before the uniform limit is reached, implying that the ground state of the kagome-lattice Heisenberg model is likely…
We report results of 51V NMR experiments on a high-quality powder sample of volborthite Cu3V2O7(OH)2/2H2O, a spin-1/2 Heisenberg antiferromagnet on a distorted kagome lattice. Following the previous experiments in magnetic fields $B$ below 12 T, the NMR measurements have been extended to higher fields up to 31 T. In addition to the two already known ordered phases (phases I and II), we found a new high-field phase (phase III) above 25 T, at which a second magnetization step has been observed. The transition from the paramagnetic phase to the antiferromagnetic phase III occurs at 26 K, which is…
Motivated by recent experimental work on FeCrAs, we study the magnetic properties of classical spin models on the hexagonal Fe$_2$P/ZrNiAl structure (space group $P{\bar{6}}2m$). When both transition metal/rare earth sites carry magnetic moments, one has alternating distorted kagome and triangular lattice layers. Each point of the triangular lattice lies at the centre of a distorted hexagon and actually corresponds to three isolated magnetic atoms: a "trimer". We show that a simple model consisting of antiferromagnetically correlated Heisenberg spins on the frustrated distorted kagome lattice …
The magnetization and specific heat measurements have been performed on single-crystalline Gd_3_Ru_4_Al_12_ with a distorted Kagome lattice structure. This spin system is regarded as an antiferromagnetic triangular lattice of XY like Heisenberg model at low temperatures. The magnetic phase diagrams indicate the existence of frustration and Z_2_ degeneracy. The magnetization and specific heat imply the successive phase transitions with partial disorder and a T-shaped spin structure in the ground state.
We report bulk magnetization, and elastic and inelastic neutron scattering measurements under an external magnetic field, $H$, on the weakly coupled distorted kagome system, Cu_{2}(OD)_3Cl. Our results show that the ordered state below 6.7 K is a canted antiferromagnet and consists of large antiferromagnetic $ac$-components and smaller ferromagnetic $b$-components. By first-principle calculations and linear spin wave analysis, we present a simple spin hamiltonian with non-uniform nearest neighbor exchange interactions resulting in a system of coupled spin trimers with a single-ion anisotropy t…
Despite the conceptional importance of realizing spin liquids in solid states only few compounds are known. On the other side the effect of lattice distortions and anisotropies on the magnetic exchange topology and the fluctuation spectrum are an interesting problem. We compare the excitation spectra of the two s=1/2 kagome lattice compounds volborthite and vesignieite using Raman scattering. We demonstrate that even small modifications of the crystal structure may have a huge effect on the phonon spectrum and low temperature properties.
High intensity pulsed neutron scattering reveals a new set of magnetic excitations in the pinwheel valence bond solid state of the distorted kagome lattice antiferromagnet Rb$_2$Cu$_3$SnF$_{12}$. The polarization of the dominant dispersive modes (2 meV $<\hbarω< $7 meV) is determined and found consistent with a dimer series expansion with strong Dzyaloshinskii-Moriya interactions ($D/J=0.18$). A weakly dispersive mode near 5 meV and shifted "ghosts" of the main modes are attributed to the enlarged unit cell below a $T=215$ K structural transition. Continuum scattering between 8 meV and 10 meV …
We report the local probe investigation of a frustrated antiferromagnet Pr$_3$BWO$_9$ with the distorted kagome lattice. Absence of magnetic order or spin freezing is indicated by the spectral analysis down to 0.3 K and specific heat measurements down to 0.09 K. The Knight shifts show an upturn behavior with the sample cooling down, which is further suppressed by external field. For the spin dynamics, gapped spin excitation is observed from the temperature dependence of spin-lattice relaxation rates, with the gap size proportional to the applied magnetic field intensity. Comparatively, an unex…
Zn-Paratacamite is a rare spin 1/2 antiferromagnetic insulator with an ideal kagome lattice structure in part of its phase diagram. As a function of Zn doping, this material undergoes a structural distortion which relieves the frustration and introduces magnetic order in the ground state, though the precise nature of the order is not clear at this point. In this paper, we present strong evidence for Neel ordering in the strongly distorted phase of Zn-Paratacamite through the application of quantum Monte-Carlo techniques. These numerical results support a recent Schwinger-boson mean field theor…
Strong metamagnetic switching and anisotropic magnetotransport in the distorted kagome magnet Tb6Ti4Al43
Indian Institute of Technology Delhi（印度理工学院德里分校）；Max-Planck-Institute for Chemical Physics of Solids（马克斯·普朗克固体化学物理研究所）；Department of Physics, Institute for Materials Research, Tohoku University（东北大学物质材料研究学院物理学系）
Strain applied to a condensed-matter system can be used to engineer its excitation spectrum via artificial gauge fields, or it may tune the system through transitions between different phases. Here we demonstrate that strain tuning of the ground state of otherwise highly degenerate frustrated systems can induce novel phases, both ordered and disordered. For the classical Heisenberg antiferromagnet on the kagome lattice, we show that weak triaxial strain reduces the degeneracies of the system, leading to a classical spin liquid with non-coplanar configurations, while stronger strain drives the …
Magnetic and thermodynamic studies on the distorted kagome magnet Pr$_3$BWO$_9$
Kirchhoff Institute for Physics, Heidelberg University（海德堡大学基尔霍夫物理研究所）；European XFEL（欧洲X射线自由电子激光设施）；Department of Physics, Indian Institute of Technology Madras（马德拉斯印度理工学院物理系）；Dresden High Magnetic Field Laboratory (HLD-EMFL), Helmholtz-Zentrum Dresden-Rossendorf（德累斯顿罗森多夫亥姆霍兹中心德累斯顿强磁场实验室）；Quantum Centre of Excellence for Diamond and Emergent Materials, Indian Institute of Technology Madras（马德拉斯印度理工学院钻石与新兴材料卓越量子中心）
We have synthesized YbPdAs with the hexagonal ZrNiAl-type structure, in which the Yb-atoms form a distorted kagome sublattice in the hexagonal basal plane. Magnetic, transport, and thermodynamic measurements indicate that YbPdAs is a low-carrier Kondo lattice compound with an antiferromagnetic transition at $T_\mathrm{N}$ = 6.6 K, which is slightly suppressed in applied magnetic fields up to 9 T. The magnetic entropy at $T_\mathrm{N}$ recovers only 33\% of $R\ln{2}$, the full entropy of the ground state doublet of the Yb-ions. The resistivity displays a $-\ln T$ dependence between 30 and 15 K,…
Successive magnetic phase transitions at $T_1$=17.5 K and $T_2$=18.5 K in Gd$_3$Ru$_4$Al$_{12}$, with a distorted kagome lattice of Gd ions, is studied using resonant X-ray diffraction with polarization analysis. It has been suggested that in this compound the $S=7/2$ spins on the nearest-neighbor Gd-triangle form a ferromagnetic trimer and the Gd lattice can be effectively considered as an antiferromagnetic triangular lattice of $S=21/2$ spin trimers [S. Nakamura et al., Phys. Rev. B 98, 054410 (2018)]. We show that the magnetic order in this system is described by an incommensurate wave vect…
The layered compound with distorted Kagome nets, Dy3Ru4Al12, was previously reported to undergo antiferromagnetic ordering below (TN=) 7 K, based on investigations on single crystals. Here, we report the results of our investigation of ac and dc magnetic susceptibility (\c{hi}), isothermal remnant magnetization (MIRM), heat-capacity, magnetocaloric effect and magnetoresistance measurements on polycrystals. The present results reveal that there is an additional magnetic anomaly around 20 K, as though the Néel order is preceded by the formation of ferromagnetic clusters. We attribute this featur…
Competing Ordering Modes in the Distorted Quantum Kagome Material Clinoatacamite Cu$_2$Cl(OH)$_3$
Technische Universität Braunschweig（布伦瑞克工业大学）；Forschungszentrum Jülich GmbH（于利希有限公司研究中心）；Okayama University（冈山大学）；Helmholtz-Zentrum Berlin für Materialien und Energie GmbH（柏林亥姆霍兹材料与能源中心有限公司）；Institut Laue-Langevin（朗之万研究所）；Federal University of Parana（巴拉那联邦大学）；Université Paris-Saclay（巴黎萨克雷大学）；PSI Center for Neutron and Muon Sciences（瑞士保罗谢勒研究所中子与缪子科学中心）
Experimental studies of high-purity kagome-lattice antiferromagnets (KAFM) are of great importance in attempting to better understand the predicted enigmatic quantum spin-liquid ground state of the KAFM model. However, realizations of this model can rarely evade magnetic ordering at low temperatures due to various perturbations to its dominant isotropic exchange interactions. Such a situation is for example encountered due to sizable Dzyaloshinskii-Moriya magnetic anisotropy in YCu$_3$(OH)$_6$Cl$_3$, which stands out from other KAFM materials by its perfect crystal structure. We find evidence …
We report magnetic and electrical properties for single crystals of NdMn$_6$Sn$_6$ and SmMn$_6$Sn$_6$. They crystallize into a structure which has distorted, Mn-based kagome lattices, compared to the pristine kagome lattices in heavy-rare-earth-bearing RMn$_6$Sn$_6$ compounds. They are hightemperature ferromagnets of which the R moment is parallel with the Mn moment. We observed a large intrinsic anomalous Hall effect (AHE) that is comparable to the ferrimagnetic, heavy-R siblings in a wide range of temperature. We conclude that their intrinsic AHE is stemming from the Mn-based kagome lattice,…
We treat the ground state, elementary excitations, and neutron scattering cross section for a system of trimers consisting of three tightly bound spins 1/2 on a distorted Kagomé lattice, subject to isotropic nearest neighbor (usually antiferromagnetic) Heisenberg interactions. The interactions between trimers are assumed to be weak compared to the intra trimer interactions. We compare the spin-wave excitation spectrum of trimers with that obtained from standard spin-wave theory and attribute the differences at low energy to the fact that the trimer formulation includes exactly the effects of i…
The magnetization process of the S=1 and 1/2 kagome Heisenberg antiferromagnet is studied by means of the numerical exact diagonalization method. It is found that the magnetization curve at zero temperature has a plateau at 1/3 of the full magnetization. In the presence of $\sqrt{3} \times \sqrt{3}$ lattice distortion, this plateau is enhanced and eventually the ferrimagnetic state is realized. There also appear the minor plateaux above the main plateau. The physical origin of these phenomena is discussed.
In the spirit of searching for Gd-based, frustrated, rare earth magnets, we have found antiferomagnetism (AF) in GdPtPb which crystallizes in the ZrNiAl-type structure that has a distorted Kagomé lattice of Gd-triangles. Single crystals were grown and investigated using structural, magnetic, transport and thermodynamic measurements. GdPtPb orders antiferromagnetically at 15.5 K arguably with a planar, non-collinear structure. The high temperature magnetic susceptibility data reveal an "anti-frustration" behavior having a frustration parameter, $|f|$ = $|Θ|$/ $T_N$ = 0.25, which can be explaine…
Frustrated spin systems on Kagome lattices have long been considered to be a promising candidate for realizing exotic spin liquid phases. Recently, there has been a lot of renewed interest in these systems with the discovery of materials such as Volborthite and Herbertsmithite that have Kagome like structures. In the presence of an external magnetic field, these frustrated systems can give rise to magnetization plateaus of which the plateau at $m=\frac{1}{3}$ is considered to be the most prominent. Here we study the problem of the antiferromagnetic spin-1/2 quantum XXZ Heisenberg model on a Ka…
The two-dimensional Ising model on a distorted Kagomé lattice is studied by means of exact solutions and the tensor renormalisation group (TRG) method. The zero-field phase diagrams are obtained, where three phases such as ferromagnetic, ferrimagnetic and paramagnetic phases, along with the second-order phase transitions, have been identified. The TRG results are quite accurate and reliable in comparison to the exact solutions. In a magnetic field, the magnetization ($m$), susceptibility and specific heat are studied by the TRG algorithm, where the $m=1/3$ plateaux are observed in the magnetiz…
We present the crystal structure and magnetic properties of Y$_{3}$Cu$_{9}$(OH)$_{19}$Cl$_{8}$, a stoichiometric frustrated quantum spin system with slightly distorted kagome layers. Single crystals of Y$_{3}$Cu$_{9}$(OH)$_{19}$Cl$_{8}$ were grown under hydrothermal conditions. The structure was determined from single crystal X-ray diffraction and confirmed by neutron powder diffraction. The observed structure reveals two different Cu-positions leading to a slightly distored kagome layer in contrast to the closely related YCu$_{3}$(OH)$_{6}$Cl$_{3}$. Curie-Weiss behavior at high-temperatures w…
Magnetic structure and high-field magnetization of the distorted kagome lattice antiferromagnet Cs$_2$Cu$_3$SnF$_{12}$
Mahidol University（玛希隆大学）；ThEP, Commission of Higher Education（高等教育委员会理论物理中心）；Osaka Prefecture University（大阪府立大学）；Phranakhon Rajabhat University（佛统皇家大学）；Radboud University（拉德堡德大学）；Neutron Science Laboratory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK)（高能加速器研究机构物质结构科学研究所中子科学实验室）
We study the magnetization process of the spin-$1/2$ Heisenberg antiferromagnet on a distorted square-kagome lattice by the numerical-diagonalization method. The magnetization jump at one-third of the height of the saturation is examined in detail; we find that the jump becomes larger when a small distortion is switched on and that it is accompanied by an abrupt change in lines along microscopic spin directions. Our finite-size results successfully confirm that the magnetization jump in a spin-isotropic system is a macroscopic jump that survives in the thermodynamic limit and that the changes …
We investigate the magnetic ground state of Sm$_3$BWO$_9$ with the distorted kagome lattice. A magnetic phase transition is identified at $T_N=0.75$ K from the temperature dependence of specific heat. From $^{11}$B nuclear magnetic resonance (NMR) measurements, an incommensurate magnetic order is shown by the double-horn type spectra under a $c$-axis magnetic field. While, absence of line splitting is observed for field oriented within the $ab$-plane, indicating the incommensurate modulation of the internal field strictly along $c$-axis. From the spin dynamics, the critical slowing down behavi…
We investigate the magnetism of a previously unexplored distorted spin-1/2 kagome model consisting of three symmetry-inequivalent nearest-neighbor antiferromagnetic Heisenberg couplings Jhexagon, J and J', and uncover a rich ground state phase diagram even at the classical level. Using analytical arguments and numerical techniques we identify a collinear Q = 0 magnetic phase, two unusual non-collinear coplanar Q = (1/3,1/3) phases and a classical spin liquid phase with a degenerate manifold of non-coplanar ground states, resembling the jammed spin liquid phase found in the context of a bond-di…
Neutron scattering measurements have been performed on deuterated powder samples of claringbullite and Zn-doped claringbullite (Zn$_x$Cu$_{4-x}$(OD)$_{6}$FCl). At low temperatures, claringbullite Cu$_4$(OD)$_{6}$FCl forms a distorted pyrochlore lattice with long-range magnetic order and spin-wave-like magnetic excitations. Partial Zn doping leads to the nominal ZnCu$_3$(OD)$_{6}$FCl compound, a geometrically frustrated spin-1/2 kagome antiferromagnet that shows no transition to magnetic order down to 1.5 K. The magnetic excitations form a gapless continuum, a signature of fractional excitation…
