One-dimensional Magnets Research Articles

Exploring two-dimensional coherent spectroscopy with exact diagonalization: Spinons and confinement in one-dimensional quantum magnets

Exploring two-dimensional coherent spectroscopy with exact diagonalization: Spinons and confinement in one-dimensional quantum magnets

Analogous Chain Selenite Chlorides Ba2M(SeO3)2Cl2 (M = Cu2+, Ni2+, Co2+, Mn2+) and Pb2Cu(SeO3)2Cl2 with Tunable Spin S: Syntheses and Characterizations.

A series of analogous chain selenite chlorides Ba2M(SeO3)2Cl2 (M = Cu 1, Ni 2, Co 3, Mn 4) and Pb2Cu(SeO3)2Cl2 5 with tunable spin S from S = 1/2 to S = 5/2 have been hydrothermally synthesized and characterized. These analogues crystallized in the orthorhombic Pnnm space group (monoclinic P21/n space group for 5) all containing M2+-SeO3-M2+ spin chains, which are further separated by the Ba2+ ions (Pb2+ for 5). The magnetic susceptibility results of 1, 2, and 5 show broad maxima around 80.0, 18.9, and 78.0 K, respectively, indicating good one-dimensional (1D) magnetism. Meanwhile, no long-range order (LRO) is observed down to 2 K for both 1 and 5, while the isostructural compounds 2, 3, and 4 exhibit LRO at 3.4 K, 10.8 K, and 5.7 K, respectively, which are further confirmed by the heat capacity and electron spin resonance results, as well as the observed spin-flop transitions in the M-H curves measured at 2 K below TN. The magnetizations of 1-5 at 7 T are still far from saturation. In addition, thermal stability and FT-IR and UV-vis-NIR spectroscopy of 1-5 are reported.

Anisotropic 2D van der Waals Magnets Hosting 1D Spin Chains.

The exploration of 1D magnetism, frequently portrayed as spin chains, constitutes an actively pursued research field that illuminates fundamental principles in many-body problems and applications in magnonics and spintronics. The inherent reduction in dimensionality often leads to robust spin fluctuations, impacting magnetic ordering and resulting in novel magnetic phenomena. Here, structural, magnetic, and optical properties of highly anisotropic 2D van der Waals antiferromagnets that uniquely host spin chains are explored. First-principle calculations reveal that the weakest interaction is interchain, leading to essentially 1D magnetic behavior in each layer. With the additional degree of freedom arising from its anisotropic structure, the structure is engineered by alloying, varying the 1D spin chain lengths using electron beam irradiation, or twisting for localized patterning, and spin textures are calculated, predicting robust stability of the antiferromagnetic ordering. Comparing with other spin chain magnets, these materials are anticipated to bring fresh perspectives on harvesting low-dimensional magnetism.

Quantum critical fluctuations in a transverse-field Ising magnet

CoNb2O6 is a model system for a spin-1/2 one-dimensional (1D) transverse-field Ising magnet (TFIM) with a rather low three-dimensional (3D) Néel ordering temperature at TN=2.95 K. We studied CoNb2O6 using ultrasound measurements down to 0.3 K in transverse magnetic fields applied along the b direction. Upon entering the 3D ordered state, we observe pronounced anomalies in the transverse acoustic mode c 66. In particular, from 1.3 to 1.5 K and around 4.7 T, this mode reveals an almost diverging softening, which is considerably reduced at lower and higher magnetic fields. We interpret this as an influence of quantum critical fluctuations emerging from the quantum critical point (QCP) of the 1D Ising spin chains at about 4.75 T, which lies below the QCP of the 3D ordering at about 5.4 T. This is clear experimental evidence of the predicted generic phase diagram for a TFIM with superimposed 3D ordering.

Chains of atoms embedded into transition metal dichalcogenides as one-dimensional half-metallic magnets

Chains of atoms embedded into transition metal dichalcogenides as one-dimensional half-metallic magnets

Field-induced Bose–Einstein condensation in zigzag spin chain KGaCu(PO4)2

Single crystals of GaKCu(PO4)2 were synthesized using the hydrothermal method, and subsequent measurements of specific heat, magnetic susceptibility, and high-field magnetization were performed. A broad peak is observed in the magnetic susceptibility and specific heat curves, with the maximum values appearing at about 11.5 K and 5.29 K, respectively. The highest maximum peak value of susceptibility is observed when the magnetic field is applied along the c-axis, followed by the a-axis, b-axis, and polycrystalline samples. These indicate that the system exhibits one-dimensional magnetism and the magnetic easy axis is the c axis. The magnetization at 2 K reveals the occurrence of a field-induced Bose–Einstein condensation (BEC) phase within the magnetic field range of approximately 8−12 T. High-field magnetization up to 40 T indicates that the compound reaches magnetization saturation as the field exceeds H s = 12 T. Through systematic measurements, a field-temperature (H−T) phase diagram was constructed, and dome-like phase boundaries were observed. The findings suggest that GaKCu(PO4)2 is a spin gap system and a promising candidate for studying BEC of magnons due to its phase transition boundary occurring at low magnetic fields.

Ferrocenyl-substituted nitronyl nitroxide in the design of one-dimensional magnets.

By the reaction of M(hfac)2 (M = Mn(II), Co(II), Cu(II), and Zn(II); hfac is the hexafluoroacetylacetonate anion) and ferrocenyl-substituted nitronyl nitroxide (L), we succeeded in the synthesis of stable heterospin complexes: mononuclear [Zn(hfac)2L], trinuclear {[Cu(hfac)2]3L2} and chain polymer [Mn(hfac)2L]n and [Co(hfac)2L]n. The specific steric bulkiness of the ferrocenyl substituent leads to the formation of trans-type coordination polyhedra in the [Mn(hfac)2L]n and [Co(hfac)2L]n chains. The introduction of the ferrocene substituent leads to an effective weakening of intermolecular or interchain magnetic exchange coupling. Ferrimagnetic ordering was observed for one-dimensional complexes [M(hfac)2L]n (M = Mn(II), Co(II)). [Co(hfac)2L]n exhibits features of single-chain magnet behaviour: slow relaxation of magnetization below 13 K is associated with a high coercive field (54 kOe at 2 K).

Effect of Dephasing on the Current through a Periodically Driven Quantum Point Contact

We consider two one-dimensional quantum XX magnets linked by a periodically driven quantum point contact. If magnets are initially polarized in opposite directions, one expects that a spin current through the quantum point contact will establish. It has been shown recently [Phys. Rev. B 103, L041405 (2021)] that, in fact, when the driving frequency exceeds a critical value, the current halts completely, the quantum point contact being effectively insulating. Here we enquire how this picture is affected by quantum dephasing. Our findings reveal that any nonzero dephasing restores the current.

Emergent electric field from magnetic resonances in a one-dimensional chiral magnet

Emergent electric field from magnetic resonances in a one-dimensional chiral magnet

Microscopic details of two-dimensional spectroscopy of one-dimensional quantum Ising magnets

Microscopic details of two-dimensional spectroscopy of one-dimensional quantum Ising magnets

Correlations in randomly stacked solids.

Packing of spheres is a problem with a long history dating back to Kepler's conjecture in 1611. The highest density is realized in face-centered-cubic (FCC) and hexagonal-close-packed (HCP) arrangements. These are only limiting examples of an infinite family of maximal-density structures called Barlow stackings. They are constructed by stacking triangular layers, with each layer shifted with respect to the one below. At the other extreme, Torquato-Stillinger stackings are believed to yield the lowest possible density while preserving mechanical stability. They form an infinite family of structures composed of stacked honeycomb layers. In this article, we characterize layer-correlations in both families when the stacking is random. To do so, we take advantage of the Hägg code-a mapping between a Barlow stacking and a one-dimensional Ising magnet. The layer correlation is related to a moment-generating function of the Ising model. We first determine the layer correlation for random Barlow stacking, finding exponential decay. We next introduce a bias favoring one of two stacking chiralities-equivalent to a magnetic field in the Ising model. Although this bias favors FCC ordering, there is no long-ranged order as correlations still decay exponentially. Finally, we consider Torquato-Stillinger stackings, which map to a combination of an Ising magnet and a three-state Potts model. With random stacking, the correlations decay exponentially with a form that is similar to the Barlow problem. We discuss relevance to ordering in clusters of stacked solids and for layer-deposition-based synthesis methods.

Multifunctional properties of a polar spin chain compound [N(C3H7)4][Cu(C8H4NO4)]·H2O exhibiting both one-dimensional magnetism and nonlinear optical activity

Functional materials with multiple properties are urgent to be explored to reach high requirements for applications nowadays. In this work, a new multifunctional one-dimensional (1D) chain compound [N(C3H7)4][Cu(ohpma)]·H2O 1 (ohpma = deprotonated N-(2-hydoxyphenyl)oxamic acid) exhibiting both 1D antiferromagnetic and nonlinear optical properties, which are both originated from the same polar [Cu(C8H4NO4)] magnetic units, has been successfully synthesized by evaporation at room temperature. Bis-polydentate nature of the (ohpma)3− ligand with constrained tridentate and bidentate coordination sites conducts Cu2+ ions coordinating in different geometries and forms 1D chains along the c axis, which are further separated by the [N(C3H7)4]+ cations. And the 1D magnetic chains further exhibit noncentrosymmetric polar arrangement. Nonlinear optical study shows polar compound 1 exhibits a discernible second-harmonic generation (SHG) efficiency and the calculation of the partial density of states indicates that the SHG efficiency of 1 is mainly originated from the polar [Cu(C8H4NO4)] magnetic units. Moreover, magnetic susceptibility shows a broad maximum around 70 K with strong intrachain interaction of J/kB = −113.0 K but no long-range order is observed down to 2 K, suggesting that 1 shows a good 1D magnetism. Both good 1D magnetism and SHG activity suggest that 1 could be as a potential multifunctional material, particularly.

Quantum spin helices more stable than the ground state: Onset of helical protection

Topological magnetic structures are promising candidates for resilient information storage. An elementary example is spin helices in one-dimensional easy-plane quantum magnets. To quantify their stability, we numerically implement the stochastic Schr\"odinger equation and time-dependent perturbation theory for spin chains with fluctuating local magnetic fields. We find two classes of quantum spin helices that can reach and even exceed ground-state stability: spin-current-maximizing helices and, for fine-tuned boundary conditions, the recently discovered ``phantom helices.'' Beyond that, we show that the helicity itself (left or right rotating) is even more stable. We explain these findings by separated helical sectors and connect them to topological sectors in continuous spin systems. The resulting helical protection mechanism is a promising phenomenon for stabilizing helical quantum structures, e.g., in ultracold atoms and solid-state systems. We also identify a third type of phantom helix in the system.

One-dimensional magnetism and Rashba-like effects in zigzag bismuth nanoribbons

Discoveries of low-dimensional quantum materials have renewed interest in some of the fundamental phenomena, such as magnetism and Rashba-type spin orbit coupling. In particular, exploring these phenomena by themselves and/or in combination within one-dimensional (1D) systems is of interest for fields as disparate as spintronics and biology. For example, a better understanding of Rashba-type spin orbit coupling in 1D systems may be used to explain spin-selective electron transport in long helical molecules. In this paper, using first principle calculations, we show that each edge of a zigzag nanoribbon composed of a bismuth (Bi) bilayer is a truly 1D structure that naturally combines both 1D magnetism and Rashba-type spin orbit coupling in a single system. In particular, we study the combined effects of exchange and spin-orbit coupling in nanoribbons that are: (i) ideal freestanding, (ii) placed on a hexagonal boron nitride substrate, and (iii) decorated with N atoms. The edges of the Bi zigzag NRs can display ferromagnetic, antiferromagnetic, or noncollinear ordering, resulting in a broken quantum spin Hall state. The interplay of Rashba and exchange effects in different magnetic phases can result in different spin-dependent transport regimes.

Emergent magnetic-nonmagnetic transition in strain-tuned zigzag-edged PtSe2 nanoribbon

Magnetic responses in nonmagnetic transition metal dichalcogenides (TMDs) via reduced dimension and defect engineering continue to bring forth emergent properties and has revolutionized important technologies such as data storage and magnetic sensing. Using the first-principles calculation, we investigate the zigzag-edged ${\mathrm{PtSe}}_{2}$ (zz-${\mathrm{PtSe}}_{2}$) nanoribbon with a sizable magnetization solely at the zigzag edges and a remarkable magnetic-nonmagnetic switching induced by a small compressive uniaxial strain of about \ensuremath{-}2%. We further interpret the sudden disappearance of the magnetization by a simple but clear model simulation considering the localized quasi-one-dimensional magnetic channels mediated by metallic backgrounds along the edges. Such newly proposed strain-controlled magnetic transition through band structure engineering highlights zz-${\mathrm{PtSe}}_{2}$ as a unique candidate for controllable TMD-based one-dimensional magnets with promising advances in fundamental physics and technological opportunities in spintronics, computing, and sensors.

Solitons in low-dimensional magnets: Elementary excitations with a nontrivial dispersion law

Solitons are known to play the role of elementary excitations for one-dimensional ordered systems, like atomic chains with charge or spin ordering. The main characteristic of solitons is their dispersion relation, dependence of soliton energy on the linear momentum. Topological kink-type solitons are the simplest and most important for the description of many physical properties of one-dimensional magnets. Here we provide a detailed analysis of solitons in some general class of magnets, ferrimagnets with the spin compensation point. The nonlinear spin dynamics of ferrimagnets are examined using a nonlinear sigma-model for the antiferromagnetic vector, which is a generalization of the Landau-Lifshitz equation for ferromagnets and sigma-model for the antiferromagnets. The characteristic features of this equation are governed by the value of the compensation parameter, describing the rate of compensation of spins of sublattices. The dispersion relation for kink-type solitons appears to be quite nontrivial, including periodic dispersion law for continuum model of magnet or the presence of ending point for kink spectrum.

Successive magnetic orderings in the Ising spin chain magnet DyNi5Ge3

In this report, we investigated a new rare-earth-based one-dimensional Ising spin chain magnet $\mathrm{Dy}{\mathrm{Ni}}_{5}{\mathrm{Ge}}_{3}$ by means of magnetization, specific heat, and powder neutron diffraction measurements. Due to the crystalline electrical field splitting, the magnetic Dy ions share an Ising-like ground doublet state. Owning to the local point symmetry, these Ising moments form into two canted magnetic sublattices, which were further confirmed by the angle-dependent magnetization measurement. In zero fields, two successive antiferromagnetic phase transitions were found at temperatures ${T}_{\mathrm{N}1}=6\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ and ${T}_{\mathrm{N}2}=5\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, respectively. Only part of the moments are statically ordered in this intermediate state between ${T}_{\mathrm{N}1}$ and ${T}_{\mathrm{N}2}$. Powder neutron diffraction experiments at different temperatures were performed as well. An incommensurate magnetic propagation vector of ${\mathbf{k}}_{\mathbf{m}}=(0.5,0.4,0.5)$ was identified. The refined spin configurations through the irreducible representation analysis confirmed that these Ising spins are canted in the crystal $ab$ plane.

Absence of Normal Fluctuations in an Integrable Magnet.

We investigate dynamical fluctuations of transferred magnetization in the one-dimensional lattice Landau-Lifshitz magnet with uniaxial anisotropy, representing an emblematic model of interacting spins. We demonstrate that the structure of fluctuations in thermal equilibrium depends radically on the characteristic dynamical scale. In the ballistic regime, typical fluctuations are found to follow a normal distribution and scaled cumulants are finite. In stark contrast, on the diffusive and superdiffusive timescales, relevant, respectively, for the easy-axis and isotropic magnet at vanishing total magnetization, typical fluctuations are no longer Gaussian and, remarkably, scaled cumulants are divergent. The observed anomalous features disappear upon breaking integrability, suggesting that the absence of normal fluctuations is intimately tied to the presence of soliton modes. In a nonequilibrium setting of the isotropic magnet with weakly polarized step-profile initial state we find a slow drift of dynamical exponent from the superdiffusive towards the diffusive value.

Spatiotemporal Crossover between Low- and High-Temperature Dynamical Regimes in the Quantum Heisenberg Magnet.

The stranglehold of low temperatures on fascinating quantum phenomena in one-dimensional quantum magnets has been challenged recently by the discovery of anomalous spin transport at high temperatures. Whereas both regimes have been investigated separately, no study has attempted to reconcile them. For instance, the paradigmatic quantum Heisenberg spin-1/2 chain falls at low temperature within the Tomonaga-Luttinger liquid framework, while its high-temperature dynamics is superdiffusive and relates to the Kardar-Parisi-Zhang universality class in 1+1 dimensions. This Letter aims at reconciling the two regimes. Building on large-scale matrix product state simulations, we find that they are connected by a temperature-dependent spatiotemporal crossover. As the temperature T is reduced, we show that the onset of superdiffusion takes place at longer length and timescales ∝1/T. This prediction has direct consequences for experiments including nuclear magnetic resonance: it is consistent with earlier measurements on the nearly ideal Heisenberg S=1/2 chain compound Sr_{2}CuO_{3}, yet calls for new and dedicated experiments.

Structure, phase transition and properties of the one-dimensional antiferromagnet Cu(2,6-dimethylpyrazine)Br2.

We report the crystal structure and properties of the one-dimensional S = 1/2 antiferromagnet Cu(2,6-dimethylpyrazine)Br2 with strong intra-chain exchange. At room temperature, its linear spin chains are formed by Cu2+ ions via the non-bonding Br⋯Br contacts. Interestingly, a phase transition from Pmmn to P21/n structure occurs at TS ≈ 248 K below which the [CuBr2]n spin chains become non-linear and the magnetic susceptibility abruptly increases, reflecting the weakening of antiferromagnetic exchange strength. This result evidences the Goodenough–Kanamori rules which claim that a linear super-exchange pathway produces stronger antiferromagnetic coupling. From magnetic susceptibility measurements we find the average intra-chain exchange strength is J/kB ≈ −88.18 K in the low temperature phase. Both magnetic and specific measurements show the absence of magnetic ordering down to 2 K, implying the excellent magnetic one-dimensionality of Cu(2,6-dimethylpyrazine)Br2. We also performed ultra-violet (UV) absorption and photoluminescence measurements which give a semiconducting band gap Δ ≈ 2.79 eV which is consistent with theoretical calculations.