Spin Ladder Compound Research Articles

Structure and Magnetic Properties of a Family of Two-Leg Spin Ladder Compounds Ba2RE2Ge4O13 (RE = Pr, Nd, and Gd-Ho).

Compared with the intensive investigation on 3d transition metal (TM)-based spin ladder compounds, less attention has been paid to the ones constructed by rare earth (RE) ions. Herein, we report a family of RE-based spin ladder compounds Ba2RE2Ge4O13 (RE = Pr, Nd, Gd-Ho) crystallized into a monoclinic structure with the space group C2/c. The RE ions are arranged on a two-leg spin ladder motif along the b-axis, where the rung and leg exchange interactions are bridged via RE-O-RE pathways and RE-O-Ge-O-RE routes, respectively. Moreover, the much shorter rung distance in RE2O12 dimer units than the leg distance suggests that Ba2RE2Ge4O13 compounds are strong-rung spin ladder systems. All of the synthesized Ba2RE2Ge4O13 (RE = Pr, Nd, Gd-Ho) compounds exhibit dominant antiferromagnetic (AFM) interactions and the absence of magnetic order down to 1.8 K. Among the family members, Ba2Dy2Ge4O13 can be described by Jeff = 1/2 Kramers doublet states, and the low-temperature specific heat indicates the coexistence of the spin-dimerized state with a broad maximum at ∼2.4 K and long-range AFM order with TN = 0.81 K. This family of Ba2RE2Ge4O13 compounds thereby provides a rare platform to investigate the novel spin ladder physics constructed by 4f electrons.

Enhancement of charge storage capacity in two-leg pseudo-spin ladder CaCu2O3 compound through Li-doping

Nanostructured 2-leg pseudo spin-ladder compound CaCu2O3 has been synthesized by chemical co-precipitation method and a significant improvement in its charge storage capacity has been realized through Li-doping. The fabricated electrode based on Li-doped CaCu2O3 exhibited higher specific capacitance of 321.26 F/g at 1.5 A g-1 when compared to that of 205.45 F/g for undoped CaCu2O3 system. Moreover, the electrode revealed an excellent cyclic stability (5000 cycles) with capacitance retention of 91.96 % of its initial value. An asymmetric supercapacitor fabricated using nano-flakes shaped Li-CaCu2O3 and activated carbon showed a notable energy density of 36.72 Wh/kg and power density of 1406 W/kg which maintains the energy density of 7.81 Wh/kg even at higher power density of 7031.25 W/kg. Among various Li-doped samples, 2.5 wt.% Li-CaCu2O3 exhibited the best storage capacity. This improvement has been attributed to the intrinsic off-stoichiometric (Ca0.86Cu2.14O2.93) and spin ladder structure of CaCu2O3 which allows Li to intercalate and improve the storage performance. Moreover, higher reactive surface area due to nano-flake morphology and porous structure of Li-CaCu2O3 may enhance the permeability of electrolytic ions, thereby improving the performance of the fabricated supercapacitor compared to undoped CaCu2O3 with rod-like morphology. These findings underscore the potential of Li-CaCu2O3 as a promising candidate material for fabricating supercapacitor devices.

Enhanced magnon thermal transport in yttrium-doped spin ladder compounds Sr14−xYxCu24O41

Magnons are quasiparticles of spin waves, carrying both thermal energy and spin information. Controlling magnon transport processes is critical for developing innovative magnonic devices used in data processing and thermal management applications in microelectronics. The spin ladder compound Sr14Cu24O41 with large magnon thermal conductivity offers a valuable platform for investigating magnon transport. However, there are limited studies on enhancing its magnon thermal conductivity. Herein, we report the modification of magnon thermal transport through partial substitution of strontium with yttrium (Y) in both polycrystalline and single crystalline Sr14−xYxCu24O41. At room temperature, the lightly Y-doped polycrystalline sample exhibits 430% enhancement in thermal conductivity compared to the undoped sample. This large enhancement can be attributed to reduced magnon-hole scattering, as confirmed by the Seebeck coefficient measurement. Further increasing the doping level results in negligible change and eventually suppression of magnon thermal transport due to increased magnon-defect and magnon-hole scattering. By minimizing defect and boundary scattering, the single crystal sample with x = 2 demonstrates a further enhanced room-temperature magnon thermal conductivity of 19Wm−1K−1, which is more than ten times larger than that of the undoped polycrystalline material. This study reveals the interplay between magnon-hole scattering and magnon-defect scattering in modifying magnon thermal transport, providing valuable insights into the control of magnon transport properties in magnetic materials.

Simultaneous determination of environmental endocrine disruptors bisphenol A and 4-nitrophenol bleached from food-contacting materials using the spin-ladder compound La2Cu2O5 modified glassy carbon electrode

Environmental endocrine-disrupting chemicals, Bisphenol A (BPA) and 4-Nitrophenol (4-NP), pose significant risks to reproductive health in both animals and humans. Here, we introduce the first utilization of the 4-leg spin ladder compound La2Cu2O5 as an electrode material for electrochemical sensor. Nanostructured La2Cu2O5 was synthesized via a straightforward Sol-Gel method and thoroughly characterized using X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and powder X-ray diffraction. La2Cu2O5 nanoparticles modified glassy carbon electrode (GCE) exhibited a significant electrocatalytic activity towards the oxidation of BPA and 4-NP in phosphate buffer saline (pH 7.0). Square wave voltammetry studies revealed lowest detection limits of 3 nM for BPA and 2.6 nM for 4-NP over a wider concentration range of 0.01–500 μM. Notably, this study marks the first utilization of La2Cu2O5 for simultaneous electrochemical detection of BPA and 4-NP, demonstrating its potential in this field. Furthermore, the sensor exhibited good sensitivity, reproducibility, and selectivity towards BPA and 4-NP, even in the presence of similar potential organic and inorganic interferents. Additionally, the newly developed sensor enabled simultaneous quantification of BPA and 4-NP in real samples such as packaged milk, river water, and plastic bottles, achieving recovery rates above 95%. Importantly, our results underscore the leaching of BPA into water from thin and thick plastics at elevated temperatures (40 °C–80 °C), emphasizing the utility of the proposed sensor for rapid and simultaneous detection of BPA and 4-NP in environmental and food matrices.

Pressure-induced electronic phase transition and superconductivity in spin-ladder compounds BaFe2(S1−x Se x )3

The discovery of high-temperature superconductivity in quasi-one-dimensional spin ladder compound BaFe2S3 has attracted great attention for facilitating study on the interplay among crystalline dimensionality, magnetism, and superconductivity. Here, we report a systematic study on the doping-dependent structure, susceptibility, and high-pressure properties of BaFe2(S1−x Se x )3. The structural analysis manifests a structural transition within the doping level of 0.18 < x< 0.29. Accompanied with this structural transition, the magnetic susceptibility behaviors change substantially, in line with the antiferromagnetic structure change from the stripe-type to the block-type. Furthermore, obvious spin glassy behaviors are observed in the low-temperature region for x⩾ 0.29. High-pressure study has revealed an explicit superconductivity signal in the undoped BaFe2S3 with a pressure of about 12.6 GPa, while no bulk superconductivity is observed for the Se-doped samples. Analysis of the pressure-dependent resistance behavior indicates a pressure-induced electronic phase transition around 18 GPa for all Se-doped samples. Finally, we have discussed the possible origin for the pressure-induced superconductivity in BaFe2(S1−x Se x )3.

Effect of iron vacancies on magnetic order and spin dynamics of the spin ladder BaFe2−δS1.5Se1.5

Quasi-one-dimensional iron chalcogenides possess various magnetic states depending on the lattice distortion, electronic correlations, and presence of defects. We present neutron diffraction and inelastic neutron scattering experiments on the spin ladder compound BaFe$_{2-\delta}$S$_{1.5}$Se$_{1.5}$ with $\sim$6% iron vacancies. The data reveal that long-range magnetic order is absent, while the characteristic magnetic excitations that correspond to both the stripe- and block-type antiferromagnetic correlations are observed. First-principles calculations support the existence of both stripe and block-type antiferromagnetic short-range order in the experimental sample. The disappearance of long-range magnetic order may be due to the competition between these two magnetic orders, which is greatly enhanced for a certain concentration of iron vacancies, which we calculate to be about 6%, consistent with the measured iron vacancy concentration. Our results highlight how iron vacancies in the iron-based spin ladder system strongly influence the magnetic ground state.

LT Scaling in Depleted Quantum Spin Ladders.

Using a combination of neutron scattering, calorimetry, quantum MonteCarlo simulations, and analytic results we uncover confinement effects in depleted, partially magnetized quantum spin ladders. We show that introducing nonmagnetic impurities into magnetized spin ladders leads to the emergence of a new characteristic length L in the otherwise scale-free Tomonaga-Luttinger liquid (serving as the effective low-energy model). This results in universal LT scaling of staggered susceptibilities. Comparison of simulation results with experimental phase diagrams of prototypical spin ladder compounds bis(2,3-dimethylpyridinium)tetrabromocuprate(II) (DIMPY) and bis(piperidinium)tetrabromocuprate(II) (BPCB) yields excellent agreement.

Pressure-Induced Superconductivity in Iron-Based Spin-Ladder Compound BaFe2+δ(S1-xSex)3.

The iron-based superconductors had a significant impact on condensed matter physics. They have a common structural motif of a two-dimensional square iron lattice and exhibit fruitful physical properties as a strongly correlated electron system. During the extensive investigations, quasi-one-dimensional iron-based spin-ladder compounds attracted much attention as a platform for studying the interplay between magnetic and orbital ordering. In these compounds, BaFe2S3 and BaFe2Se3 were found to exhibit superconductivity under high pressure, having a different crystal and magnetic structure at low temperature. We report a brief review of the iron-based spin-ladder compound and recent studies for BaFe2+δ(S1−xSex)3. BaFe2(S0.75 Se0.25)3 is in the vicinity of the boundary of two different magnetic phases and it is intriguing to perform high pressure experiments for studying superconductivity, since effects of large magnetic fluctuations on superconductivity are expected. The effect of iron stoichiometry on the interplay between magnetism and superconductivity is also studied by changing the iron concentration in BaFe2+δSe3.

Role of Grain Size on Magnon and Phonon Thermal Transport in the Spin Ladder Compound Ca9La5Cu24O41

The antiferromagnetic spin ladder compound Ca9La5Cu24O41 is a promising material for thermal management applications due to its largest magnon thermal conductivity near room temperature among all magnetic materials. It remains elusive how boundary and defect scattering processes affect the magnon and phonon thermal transport in this material. Here, we report the thermal transport investigation of Ca9La5Cu24O41 polycrystals with different grain sizes as compared with single crystals. The thermal conductivity measurements reveal the contrasting role of size effects on magnon and phonon transport. As the average grain size decreases from 4.2 to 0.83 μm, the lattice thermal conductivity of polycrystalline Ca9La5Cu24O41 below about 100 K is significantly suppressed, due to the enhanced phonon-boundary scattering. In comparison, the magnon thermal transport is less affected by grain size. According to kinetic model analysis, the magnon mean free paths of two polycrystals are found to be much smaller than the single-crystal values, which is attributed to the magnon-defect scattering instead of magnon-boundary scattering. The obtained magnon mean free path of about 65 Å near 100 K is comparable to the lattice constant of the unit cell along the spin ladder direction, suggesting possible magnon localization in the disordered polycrystalline samples. These results offer useful insights into the development of magnetic materials for spin caloritronic and thermal management applications.

Synthesis, Structure and Properties of a New Strong‐Rung Spin Ladder Compound Cu(2‐Ethylpyrazine)Br2

AbstractWe report the structure and magnetism of a newly synthesized coordination polymer Cu(2‐ethylpyrazine)Br2. Its crystal structure was determined by both single crystal and powder X‐ray diffractions. We find the compound crystallizes in the space group C2 with a ladder structure in which the copper ions are bridged by bromide ions and 2‐ethylpyrazine molecules along the rung and rail direction, respectively. The magnetic susceptibility is consistent with the strong‐rung spin ladder model which yields Jrung/kB=−33.819(1) K, Jrail/kB=−25.206(3) K. The obtained spin gap is Δ=18.01 K. Both magnetic susceptibility and heat capacity measurements show the absence of low range magnetic order down to 2 K, indicating weak inter‐ladder coupling in the compound.

Critical temperature and low-energy excitations in gapped spin systems with defects

We discuss theoretically the magnetically ordered phase induced by magnetic and nonmagnetic impurities in three-dimensional and quasi-low-dimensional systems with singlet ground states separated by a gap from excited triplet states. Using ideas of the percolation theory, we estimate the transition temperature $T_N(n)$ to the N\'eel phase at a small concentration $n$ of defects, derive the density of states of low-energy elementary excitations, and examine the contribution of these excitations to the specific heat and magnetization. Our expressions for $T_N(n)$ and for the specific heat describe well available experimental findings obtained in various appropriate systems: spin-$\frac12$ dimer materials, spin-ladder compounds, spin-Peierls and Haldane chain materials. However, our expression for $T_N(n)$ differs considerably from many of those proposed before.

Synthesis and Magnon Thermal Transport Properties of Spin Ladder Sr14Cu24O41 Microstructures

AbstractThe spin ladder compound (Sr,Ca,La)14Cu24O41 exhibits an incommensurate layered structure with strong antiferromagnetic coupling. Besides intriguing superconducting behavior, recent experiments on bulk Sr14Cu24O41 single crystals have revealed a remarkable magnon thermal conductivity, which is the largest above 100 K among all known quantum magnets. Although bulk (Sr,Ca,La)14Cu24O41 crystals have been synthesized and studied extensively, there have been few reports on the synthesis and magnon thermal transport investigation of their microstructures. Here, the synthesis and thermal transport properties of Sr14Cu24O41 microrods are reported. Electron microscopy studies indicate that these microrods synthesized by a coprecipitation method are single crystals grown preferentially along the ladder axis. Based on a four‐probe thermal transport measurement, the thermal conductivity of the microrods reveals appreciable magnon transport in the microstructures. According to a kinetic model analysis, magnon transport in the microrods is suppressed mainly by increased point defect scattering compared to the bulk crystals, whereas surface scattering is negligible for anisotropic 1D magnon transport along the ladder. Moreover, the thermal conductivity is enhanced after annealing as a result of reduced oxygen vacancies. These results help to build the foundation for future heterogeneous integration of magnetic microstructures in microscale devices for the transport of energy and quantum information.

Nonsuperconducting electronic ground state in pressurized BaFe2S3 and BaFe2S2.5Se0.5

We report a comprehensive study of the spin ladder compound BaFe$_2$S$_{2.5}$Se$_{0.5}$ using neutron diffraction, inelastic neutron scattering, high pressure synchrotron diffraction, and high pressure transport techniques. We find that BaFe$_2$S$_{2.5}$Se$_{0.5}$ possesses the same $Cmcm$ structure and stripe antiferromagnetic order as does BaFe$_2$S$_3$, but with a reduced N{\'{e}}el temperature of $T_N=98$ K compared to 120 K for the undoped system, and a slightly increased ordered moment of 1.40$\mu_B$ per iron. The low-energy spin excitations in BaFe$_2$S$_{2.5}$Se$_{0.5}$ are likewise similar to those observed in BaFe$_2$S$_{3}$. However, unlike the reports of superconductivity in BaFe$_2$S$_3$ below $T_c \sim 14$~K under pressures of 10~GPa or more, we observe no superconductivity in BaFe$_2$S$_{2.5}$Se$_{0.5}$ at any pressure up to 19.7~GPa. In contrast, the resistivity exhibits an upturn at low temperature under pressure. Furthermore, we show that additional high-quality samples of BaFe$_2$S$_3$ synthesized for this study likewise fail to become superconducting under pressure, instead displaying a similar upturn in resistivity at low temperature. These results demonstrate that microscopic, sample-specific details play an important role in determining the ultimate electronic ground state in this spin ladder system. We suggest that the upturn in resistivity at low temperature in both BaFe$_2$S$_3$ and BaFe$_2$S$_{2.5}$Se$_{0.5}$ may result from Anderson localization induced by S vacancies and random Se substitutions, enhanced by the quasi-one-dimensional ladder structure.

Nanostructured Spin Ladder Compound CaCu2O3 based Gas Sensor for the Detection of Volatile Organic Compounds

Several volatile organic compounds (VOCs) are found in human breath and the concentrations of such VOCs are usually measured to be at sub-ppm level or even lower for healthy human beings. Abnormal concentrations of the breath VOCs are reported to correlate with unhealthy/injurious body/organ conditions; for instance, acetone gas for diabetes, trimethylamine for uremic patients and ammonia gas for renal disease. Hence, VOCs can potentially be used as disease-specific biomarkers for non-invasive early detection or monitoring from breath. Acetone can be produced via the fatty acid oxidation in diabetes and ketoacidosis lack of insulin. Excessive acetone circulating in the blood system is excreted from the lungs. Higher acetone concentration ranges from 1.7 ppm to 3.7 ppm could be detected in breath for those who are diabetic, while the breath of healthy human typically contains less than 0.8 ppm. Gas sensors with sub-ppm acetone detection capacity play an important role in the development of non-invasive monitors or early diagnosis of potential diabetic patients. Up to date, various gas sensors have been successfully developed to detect acetone by controlling the morphology of nanomaterials or introducing the noble metals into nanoparticles. Although, these sensors had achieved the purpose to detect acetone gas, the high operating temperature, higher-energy cost, and the long response time still limit their further applications in practice. Great effort has been made to improve that, by choosing novel material. In order to solve these problems, the present work will focus on the design and development of gas sensors based on new nanomaterials CaCu2O3 offer extremely large surface-to-volume ratio, and the possibility to modify their surface reactivity to attain high sensitivity at low concentration (ppt or lower) required for detection of acetone.CaCu2O3 nanoparticles were synthesized by microwave irradiation method. The structural, morphological, electrical properties were studied by HRSEM, XRD and electrical measurements. The response of CaCu2O3 sensors to acetone at different operating temperatures is reported. It can be noted that the maximum of response to acetone observed at 200°C. The resistance change of the sensor to temperature change is quick and the baseline stabilization is attained in a brief time. The response of the sensor to acetone pulses is reversible and fast (τres ~ 5 seconds). Further, a considerable decrease has been observed in the recovery time (τrec ~ 20 seconds), which is another key advantage of this CaCu2O3.The reproducibility and repeatability are other important factors for a acetone gas sensor. The cycling performance of the fabricated sensor at 200°C shows that the response to 100 ppm of acetone is the same when the measurements were repeated for 10 times consecutively, indicating the excellent reproducibility. Furthermore, the long-term stability of the sensor was also evaluated for many months, and the responses are nearly the same, demonstrating the good stability of the developed sensor.CaCu2O3 nanorods have been prepared by microwave irradiation method and their gas sensing properties towards acetone and ethanol are investigated. All the fabricated sensors show reversible resistance changes while exposed to acetone. The gas sensing measurements of CaCu2O3 sensor exhibited high sensitivity and good selectivity towards acetone. Further, the fabricated sensor showed remarkable increase in sensor response and recovery times. The developed CaCu2O3 sensor is most promising candidate for highly sensitive and selective detection of acetone for medical applications.

Terahertz spectroscopic signature of the charge density wave in the spin-ladder compound, Sr14Cu24O41

We provide spectroscopic evidence for the charge density wave (CDW) phason mode at ≈0.93 THz in the two-leg, spin-1/2 ladders of Sr14Cu24O41 using terahertz time-domain spectroscopy. We find that annealing in an oxygen atmosphere or doping with a low concentration of Co (≾1%) does not affect the CDW phason mode. However, Co doping at higher concentrations (10%), wherein the Co enters the ladder layers, destabilizes the CDW. We believe that the suppression of the CDW phase is due to an increase in intraladder overlap integrals through the shrinkage of interplane distance upon Co doping.

Spin Gap in β-TeVO4: a Quantum Monte Carlo Study

In this paper, we proposed a two-leg spin ladder model for the description of magnetic properties of the β-TeVO4 compound. Quantum Monte Carlo (QMC) simulation was applied to describe the temperature-dependent magnetic susceptibility data for low temperatures. The two-leg spin ladder model presents a spin gap, and we suggests that β-TeVO4 compound presents such a spin gap also, and therefore, the model proposed here can be experimentally tested by measuring the spin gap of the compound. The susceptibility phase diagram has a rounded peak in the vicinity of T ≈ 12.2 K and obeys Troyer’s law for low temperatures and Curie’s law for high temperatures. We also study the susceptibility diagram in low temperatures and found the spin gap Δ = 8.06 K. The linearization of the equation for susceptibility in low temperatures allows us to obtain the spin gap value, and such a linearization was made with the data from the QMC simulation. In all the results, there is a very good agreement with the experimental data. We also show that the spin gap is null and the susceptibility is proportional to T for low temperatures when relatively high values of the ladders’ coupling is considered. The theoretical results are compared with other studies as well as applied to describe the susceptibility phase diagram of consolidated spin ladder compound, C9H18N2CuBr4.

Magnetic-order-driven metal-insulator transitions in the quasi-one-dimensional spin-ladder compounds BaFe2S3 and BaFe2Se3

The quasi-one-dimensional spin ladder compounds, BaFe$_2$S$_3$ and BaFe$_2$Se$_3$, are investigated by infrared spectroscopy and density functional theory (DFT) calculations. We observe strong anisotropic electronic properties and an optical gap in the leg direction that is gradually filled above the antiferromagnetic (afm) ordering temperature, turning the systems into a metallic phase. Combining the optical data with the DFT calculations we associate the optical gap feature with the $p$-$d$ transition that appears only in the afm ordered state. Hence, the insulating ground state along the leg direction is attributed to Slater physics rather than Mott-type correlations.

Magnetic-Field-Induced Bound States in Spin-1/2 Ladders.

Motivated by the recently observed intriguing mode splittings in a magnetic field with inelastic neutron scattering in the spin ladder compound (C_{5}H_{12}N)_{2}CuBr_{4} (BPCB), we investigate the nature of the spin ladder excitations using a density matrix renormalization group and analytical arguments. Starting from the fully frustrated ladder, for which we derive the low-energy spectrum, we show that bound states are generically present close to k=0 in the dynamical structure factor of spin ladders above H_{c1}, and that they are characterized by a field-independent binding energy and an intensity that grows with H-H_{c1}. These predictions are shown to explain quantitatively the split modes observed in BPCB.

Fast and selective detection of volatile organic compounds using a novel pseudo spin-ladder compound CaCu2O3

A novel pseudo spin-ladder CaCu2O3 compound (2-leg) based conductometric gas sensor has been proposed, for the first time, for the detection of volatile organic compounds (VOCs); (a) the proposed reaction mechanism in air, and (b) in the presence of acetone and ethanol.

Robust block magnetism in the spin ladder compound BaFe2Se3 under hydrostatic pressure

The majority of the iron-based superconductors (FeSCs) exhibit a two-dimensional square lattice structure. Recent reports of pressure-induced superconductivity in the spin-ladder system, BaFe$_2$X$_3$ (X =S,Se), introduce a quasi-one-dimensional prototype and an insulating parent compound to the FeSCs. Here we report X-ray, neutron diffraction and muon spin relaxation experiments on BaFe$_2$Se$_3$ under hydrostatic pressure to investigate its magnetic and structural properties across the pressure-temperature phase diagram. A structural phase transition was identified at a pressure of 3.7(3) GPa. Neutron diffraction measurements at 6.8(3) GPa and 120 K show that the block magnetism persists even at these high pressures. A steady increase and then fast drop of the magnetic transition temperature $T\rm_N$ and greatly reduced moment above the pressure $P_s$ indicate potentially rich and competing phases close to the superconducting phase in this ladder system.