Physical Property Measurement System Research Articles

Improved prediction of critical currents for multi-pancake coil across variable temperature regions

With the increasing performance of the second-generation high-temperature superconducting (2G-HTS) tapes, the technology of all-REBa2Cu3O7-δ (REBCO, RE: rare earth) superconducting magnets has developed rapidly. However, the 2G-HTS magnet with hybrid cryocoolers constantly adjusts its operating temperature according to the actual demands, which involves the critical current when the magnet crosses variable temperature regions. In this paper, a modified ideal model based on the homogenization model is proposed, which can predict the critical current of 2G-HTS magnets more consistently. The in-field properties of REBCO tapes in variable temperature regions were tested by the physical property measurement system. Furthermore, the improved model was combined with the in-field properties of REBCO tapes to obtain the critical currents of a 2G-HTS multi-pancake (MP) coil at 20 K, 30 K, 65 K, and 77 K. The critical current of a multi-pancake coil at 77 K was experimentally verified. The modified ideal model uses the actual current density, which results are closer to the experimental results with an agreement of 97.3%. This new method proposed in this work is significant in quickly predicting critical currents for 2G-HTS magnets across variable temperature regions.

Laser induced ultrafast Gd 4f spin dynamics at the surface of amorphous CoxGd100-x ferrimagnetic alloys

We have investigated the laser induced ultrafast dynamics of Gd 4f spins at the surface of CoxGd100-x alloys by means of surface-sensitive and time-resolved dichroic resonant Auger spectroscopy. We have observed that the laser induced quenching of Gd 4f magnetic order at the surface of the CoxGd100-x alloys occur on a much longer time scale than that previously reported in “bulk sensitive” time-resolved experiments. In parallel, we have characterized the static structural and magnetic properties at the surface and in the bulk of these alloys by combining Physical Property Measurement System (PPMS) magnetometry with X-ray Magnetic Circular Dichroism in absorption spectroscopy (XMCD) and X-Ray Photoelectron spectroscopy (XPS). The PPMS and XMCD measurements give information regarding the composition in the bulk of the alloys. The XPS measurements show non-homogeneous composition at the surface of the alloys with a strongly increased Gd content within the first layers compared to the nominal bulk values. Such larger Gd concentration results in a reduced indirect Gd 4f spin-lattice coupling. It explains the “slower” Gd 4f demagnetization we have observed in our surface-sensitive and time-resolved measurements compared to that previously reported by “bulk-sensitive” measurements.

A comprehensive experimental and DFT analysis on thermoelectric properties of Sb, Te co-doped Bi2Se3 polycrystals

As tellurides and selenides of Bismuth are extensively used thermoelectric materials in the low-temperature range with refrigeration application, A concerted effort is put forth to boost the ZT by co-doping the pristine Bi2Se3 with antimony (Sb) on cation end and tellurium (Te) on anion side of the compound. The double sintered solid-state reaction method is employed in the preparation of Bi2Se3 and (Bi1−xSbx)2Se2.7Te0.3 polycrystalline pellets, with x = 0.02, 0.04, and 0.06. The sample exhibits a rhombohedral structure with the space group of R 3¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\overline{3 }$$\\end{document} m. FESEM and EDAX analysis are used to confirm surface morphology and elemental composition of the produced samples. The thermoelectric measurements for the pristine and co-doped samples were conducted by the physical property measurement system as well as a considerable increase in the Seebeck coefficient of − 115 µV/K is observed for 0.02 doping of the Sb which is 4.2 times greater than as for pristine (S = − 28 µV/K). Higher concentration doping (x = 0.04, 0.06) has not reflected any Seebeck coefficient advancement. In contrast, the lowest total thermal conductivity at a low-temperature regime (< 50 K) is observed for x = 0.06 doping concentration which at near room temperature increases beyond the pristine thermal conductivity; whereas, x = 0.02, 0.04 doping concentration shows a decrement in total thermal conductivity at low, at room temperature region the values are almost equivalent to that of pristine. The co-doped samples’ electrical resistivity is substantially less than pristine sample. The highest power factor of 3 × 10–4 µW/mK2 is obtained for the x = 0.02 sample. The highest ZT value for the x = 0.02 sample is almost 28 times more than a pristine sample. We conducted a study where we combined experimental and DFT methods to investigate thermoelectric properties incorporated into pristine and doped with antimony and tellurium on Bi2Se3. We have employed this combination to investigate the partial density of states, Seebeck coefficient, power factor using the Boltzmann transport equation. Theoretical thermoelectric data were derived and compared to experimental observations. Hence, using combined experimental and theoretical investigations helps to predict with higher accuracy of thermoelectric properties of semiconducting materials.

Enhanced Thermoelectric Performance of Nanostructured 2D Tin Telluride.

A lot of experimental studies are conducted on theoretically predicted thermoelectric 2D materials. Such materials can pave the way for charging ultra-thin electronic devices, self-charging wearable devices, and medical implants. This study systematically explores the thermoelectric attributes of bulk and 2D nanostructured Tin Telluride (SnTe), employing experimental investigations and theoretical analyses based on semiclassical Boltzmann transport theory. The bulk SnTe is synthesized through flame melting, while the 2D SnTe is produced via liquid phase exfoliation. The comprehensive assessment of thermoelectric properties integrated experimental measurements utilizing a Physical Property Measurement System and theoretical calculations from the BoltzTraP code. Experimental thermoelectric studies show a high ZT of 0.17 for 2D SnTe when compared to bulk (0.005) at room temperature. This rise in ZT is due to the high Seebeck coefficient and low thermal conductivity of nanostructured 2D SnTe. Density functional theory (DFT) studies reveal the contribution of the density of states (DOS) and energy bandgap in enhancing the Seebeck coefficient and lowering thermal conductivity by interface scattering.

Cryogenic platform to investigate strong microwave cavity-spin coupling in correlated magnetic materials

We present a comprehensive exploration of loop-gap resonators for electron spin resonance (ESR) studies, enabling investigations into the hybridization of solid-state magnetic materials with microwave polariton modes. The experimental setup, implemented in a Physical Property Measurement System by Quantum Design, allows for measurements of ESR spectra at temperatures as low as 2 Kelvin. The versatility of continuous wave ESR spectroscopy is demonstrated through experiments on CuSO 4⋅5 H2O and MgCr2O4, showcasing the g-tensor and magnetic susceptibilities of these materials. The study delves into the challenges of fitting spectra under strong hybridization conditions and underscores the significance of proper calibration and stabilization. The detailed guide provided serves as a valuable resource for laboratories interested in exploring hybrid quantum systems through microwave resonators.

Br-Vacancies Induced Variable Ranging Hopping Conduction in High-Order Topological Insulator Bi4Br4.

The defects have a remarkable influence on the electronic structures and the electric transport behaviors of the matter, providing the additional means to engineering their physical properties. In this work, a comprehensive study on the effect of Br-vacancies on the electronic structures and transport behaviors in the high-order topological insulator Bi4Br4 is performed by the combined techniques of the scanning tunneling microscopy (STM), angle-resolved photoemission spectroscopy (ARPES), and physical properties measurement system along with the first-principle calculations. The STM results show the defects on the cleaved surface of a single crystal and reveal that the defects are correlated to the Br-vacancies with the support of the simulated STM images. The role of the Br-vacancies in the modulation of the band structures has been identified by ARPES spectra and the calculated energy-momentum dispersion. The relationship between the Br-vacancies and the semiconducting-like transport behaviors at low temperature has been established, implying a Mott variable ranging hopping conduction in Bi4Br4. The work not only resolves the unclear transport behaviors in this matter, but also paves a way to modulate the electric conduction path by the defects engineering.

Glass formation, crystallization behavior, nanoprecipitate phase, and magnetic properties of Mn-Fe-Si-B-EM (EM = Zr, Nb, V) alloys

In this paper, the as-quenched Mn55Fe15Si20B7EM3 (EM = Zr, Nb, V) amorphous ribbons were produced by the melt spinning technique. The crystallization behavior, nanoprecipitate phase evolution, and magnetic properties of the Mn-Fe-Si-B-EM (EM = Zr, Nb, V) amorphous alloys were investigated by X-ray diffraction (XRD), differential scanning calorimeter (DSC), and the quantum design dynacool-9 physical property measurement system (PPMS). The Mn55Fe15Si20B7EM3 (EM = Zr, Nb, V) amorphous alloys show two-stage crystallization behavior. In the first stage, the primary crystallization results in the formation of α-Mn + Mn6Si/Mn3Si precipitates, while in the second stage, the secondary crystallization leads to the formation of the Mn2B phase. The Mn55Fe15Si20B7Zr3 (FZ) amorphous sample shows a most significant two-stage phase transformation, which the onset temperature of the primary and that of the secondary crystallization are 625.7 °C and 681.2 °C, respectively. The FZ amorphous sample undergoes a magnetic phase transformation from the spin glass (SG) state to a paramagnetic (PM) state at approximately 28 K. As the temperature increases, the magnetic phase transition can be expressed as: SG → PM. The annealed FZ nanocrystalline sample with α-Mn + Mn6Si nano phases enters the ferromagnetic (FM) state at 27∼70 K after undergoing spin glass transformation, and the magnetic phase transition is: SG → FM → PM. The annealed Mn55Fe15Si20B7V3 nanocrystalline sample containing nano α-Mn and Mn3Si phases shows two Curie transitions at 57 K and 130 K, respectively. The magnetic phase transition behavior can be expressed as: SG → FMΙ → FMΙΙ → PM.

Low-temperature heat capacity and absolute entropy of yttrium(III) bromide (YBr3)

Abstract The heat capacity of yttrium(III) bromide (YBr3) in the temperature range from 2 K to 300 K has been determined using a Physical Property Measurement System (PPMS). From these data the absolute entropy of the compound at 298.15 K has been derived.

Design of Electrical Sheet Resistance of Thin Film Measurement System Based on GM Cryocooler in Cryogenic Temperature

The determination of the dependencies of the electrical resistivity of the thin film to temperature is of great importance both for understanding the conduction mechanism and for numerous technical applications of these films. In this work, to characterize, the electrical properties of thin films, a GM cryocooler-based automatic board temperature range electrical properties measurement system has been constructed. The system can measure multiple samples simultaneously. The cooling process was simulated using the time-discrete differencing to validate the optimized device design parameters and minimize heat losses. Furthermore, the temperature-dependent sheet resistance results were compared with the results from the physical property measurement system.

Investigation of Layered Structure Formation in MgB2 Wires Produced by the Internal Mg Coating Process under Low and High Isostatic Pressures.

Currently, MgB2 wires made by the powder-in-tube (PIT) method are most often used in the construction and design of superconducting devices. In this work, we investigated the impact of heat treatment under both low and high isostatic pressures on the formation of a layered structure in PIT MgB2 wires manufactured using the Mg coating method. The microstructure, chemical composition, and density of the obtained superconductive wires were investigated using scanning electron microscopy (SEM) with an energy-dispersive X-ray spectroscopy (EDS) analyzer and optical microscopy with Kameram CMOS software (version 2.11.5.6). Transport measurements of critical parameters were made by using the Physical Property Measurement System (PPMS) for 100 mA and 19 Hz in a perpendicular magnetic field. We observed that the Mg coating method can significantly reduce the reactions of B with the Fe sheath. Moreover, the shape, uniformity, and continuity of the layered structure (cracks, gaps) depend on the homogeneity of the B layer before the synthesis reaction. Additionally, the formation of a layered structure depends on the annealing temperature (for Mg in the liquid or solid-state), isostatic pressure, type of boron, and density of layer B before the synthesis reaction.

Effect of particle size and composition on local magnetic hyperthermia of chitosan-Mg1-xCoxFe2O4 nanohybrid.

In this study, Mg1-xCoxFe2O4 (0≤x ≤ 1 with ∆x = 0.1) or MCFO nanoparticles were synthesized using a chemical co-precipitation method and annealed at 200, 400, 600, and 800°C respectively to investigate the structural properties of the materials by X-ray diffractometer (XRD), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FTIR). Controlled annealing increased particle size for each value of x. The aim was to investigate how specific loss power (SLP) and maximum temperature (Tmax) during local magnetic hyperthermia were affected by structural alterations associated with particle size and composition. The lattice parameter, X-ray density, ionic radius, hopping length, bond length, cation-cation distance, and cation-anion distance increase with an increase in Co2+ content. Raman and FTIR spectroscopy reveal changes in cation distribution with Co2+ content and particle size. Magnetic properties measured by the physical property measurement system (PPMS) showed saturation magnetization (Ms), coercivity (Hc), remanent magnetization (Mr/Ms), and anisotropy constant (K1) of the Mg1-xCoxFe2O4 nanoparticles increase with Co2+ content and particle size. When exposed to an rf magnetic field, the nanohybrids experienced an increase in both the SLP (specific loss power) and Tmax (maximum temperature) as the particle size initially increased. However, these values reached their peak at critical particle size and subsequently decreased. This occurs since a modest increase in anisotropy, resulting from the presence of Co2+ and larger particle size, facilitates Néel and Brownian relaxation. However, for high anisotropy values and particle size, the Néel and Brownian relaxations are hindered, leading to the emergence of a critical size. The critical size increases as the Co2+ content decreases, but it decreases as the Co2+ content increases, a consequence of higher anisotropy with the increase in Co2+. Additionally, it is noteworthy that the maximum temperature (Tmax) rises as the concentration of nanohybrids grows, but the specific loss power (SLP) decreases. An increased concentration of chitosan-MCFO nanohybrids inhibits both the Néel and Brownian relaxation processes, reducing specific loss power.

Magnetic property enhancement of rare-earth-free nanocrystalline LTP-MnBi melt-spun ribbons

Rare-earth-free low-temperature-phase MnBi alloys have attracted extensive attention, but achieving high-purity and high-performance remains a challenge. In this study, a low-temperature phase (LTP) MnBi alloy was prepared through melt spinning and vacuum annealing techniques. The crystalline structure, microstructure, and magnetic properties of MnBi alloys were systematically investigated by x-ray diffraction, scanning electron microscopy, and physical property measurement system. Results showed that roller speed effectively improved the purity and coercivity of MnBi alloys. The optimization of process parameters achieved a high saturation magnetization of 70.7 A m2/kg and a significant coercivity of 2.34 T (at 450 K). It revealed that microstructure and magnetic properties were closely associated with rolling speed processes. This work serves as an exemplar for the fabrication of high-performance LTP-MnBi alloys, exhibiting its potential for high-temperature applications.

Study of dielectric polarization and electrical transport in Bi1·2Sb0·8Te0·4Se2.6 nanofilms

Studying the dielectric response of topological insulators (TIs) can unveil their unique physical mechanisms such as charge transport and spin-orbit coupling effects. However, due to the manifestation of material's topological nature and band structure primarily in nanofilm, such thickness poses challenges for dielectric testing. To date, research on TI dielectric aspects remains relatively unexplored. Therefore, this paper successfully synthesizes nanofilm of quaternary topological insulator Bi1·2Sb0·8Te0·4Se2.6 (BSTS) using laser molecular beam epitaxy (LMBE) technique. Utilizing a wide-frequency dielectric spectrometer and a comprehensive physical properties measurement system (PPMS), we measured and thoroughly analyzed the dielectric polarization and charge transport characteristics of BSTS. We observed various polarization responses in the frequency range of 101–103 Hz, with the dipole orientation gradually failing to keep pace with the frequency increase in the range of 103–105 Hz, and the relaxation polarization unable to establish itself in the range of 105–107 Hz, with polarization primarily contributed by displacement polarization. Subsequently, we further analyzed the dependence of BSTS dielectric polarization response on temperature and film thickness, which will help reveal the influence of external factors on TI dielectric response, providing crucial insights for controlling TI materials' dielectric response. This not only deepens our understanding of the fundamental physical properties of this novel material but also offers important scientific basis and technological support for its applications in quantum computing, photonics, spintronics, and other fields.

Study on Bulk-Surface Transport Separation and Dielectric Polarization of Topological Insulator Bi1.2Sb0.8Te0.4Se2.6.

This study successfully fabricated the quaternary topological insulator thin films of Bi1.2Sb0.8Te0.4Se2.6 (BSTS) with a thickness of 25 nm, improving the intrinsic defects in binary topological materials through doping methods and achieving the separation of transport characteristics between the bulk and surface of topological insulator materials by utilizing a comprehensive Physical Properties Measurement System (PPMS) and Terahertz Time-Domain Spectroscopy (THz-TDS) to extract electronic transport information for both bulk and surface states. Additionally, the dielectric polarization behavior of BSTS in the low-frequency (10-107 Hz) and high-frequency (0.5-2.0 THz) ranges was investigated. These research findings provide crucial experimental groundwork and theoretical guidance for the development of novel low-energy electronic devices, spintronic devices, and quantum computing technology based on topological insulators.

Magnetic properties of Fe intercalation FexTaSe2

Intercalation of transition metal dichalcogenides with magnetic elements has been the subject of increasing research interest, aiming to explore novel magnetic materials with anisotropy and spin-orbit coupling. In this paper, two magnetic samples with varying Fe content have been prepared using different growth conditions via the chemical vapor transport method. A comprehensive investigation of the magnetic properties of the materials has been conducted using the Physical Property Measurement System (PPMS, EvercoolⅡ-9T, Quantum Design). The results reveal distinct features in the studied materials. Fe0.12TaSe2 exhibits significant ferromagnetism with a Curie transition temperature of 50 K. However, its in-plane magnetism is weak and no significant hysteresis loop is observed below the Curie temperature. On the other hand, Fe0.25TaSe2 exhibits antiferromagnetism without any hysteresis loop and has a Néel temperature up to 130 K. This finding is quite different from the intercalated iron in FexTaS2, where only an antiferromagnetic state occurs with x larger than 0.4. Our study thus provides updated insights into the magnetic properties of this new system and serves as a reference for future investigations of TaSe2 compounds with varying iron content.

Performance study of REBCO multi-filament tapes/CORC cables prepared by reel-to-reel mechanical incision

REBCO high-temperature superconductor (HTS) has widely used in high magnetic field applications, because of the excellent critical current properties and high critical temperature. However, REBCO tape has an extremely large width-to-thickness ratio (typically in the range of 1000–10000) to cause too high power dissipation in the applications. In order to reduce the shielding current effect and AC loss generated during the application of REBCO HTS tapes, a roll-to-roll mechanical incision device was developed for the preparation of REBCO multi-filaments tapes. The microscopic morphology, critical current IC, and hysteresis loss of the tapes before and after incision were comparatively characterized using optical microscope, standard four-probe method, and physical property measurement system (PPMS) and other equipment and methods. The results show that the developed device prepares multi-filaments tapes with incision grooves depths of ∼ 30 μm and grooves widths of ∼ 20 μm on the superconducting layer, and the hysteresis loss of the 3-filaments is reduced by up to 48.6 % compared to that of the non-striated tapes under different temperature conditions. In addition, the IC of the short samples of the 3-filaments tapes was reduced by ∼ 18 % compared with that of the non-striated tapes under 77 K and self-field test conditions, whereas the samples of the 3-filaments tapes and the non-striated tapes were hand-wound respectively onto a metal core with a diameter of 5.25 mm to make a single-layer CORC cable, and there was no significant reduction in the IC of either of them.

Enhanced Photocharacteristics by Fermi Level Modulating in Sb2 Te3 /Bi2 Se3 Topological Insulator p-n Junction.

Topological insulators have recently received attention in optoelectronic devices because of their high mobility and broadband absorption resulting from their topological surface states. In particular, theoretical and experimental studies have emerged that can improve the spin generation efficiency in a topological insulator-based p-n junction structure called a TPNJ, drawing attention in optospintronics. Recently, research on implementing the TPNJ structure is conducted; however, studies on the device characteristics of the TPNJ structure are still insufficient. In this study, the TPNJ structure is effectively implemented without intermixing by controlling the annealing temperature, and the photocharacteristics appearing in the TPNJ structure are investigated using a cross-pattern that can compare the characteristics in a single device. Enhanced photo characteristics are observed for the TPNJ structure. An optical pump Terahertz probe and a physical property measurement system are used to confirm the cause of improved photoresponsivity. Consequently, the photocharacteristics are improved owing to the change in the absorption mechanism and surface transport channel caused by the Fermi level shift in the TPNJ structure.

Probing Evolution of the Flux-Pinning Landscape in REBCO Coated Conductors Caused by Gamma Irradiation Using DC and AC Magnetometry: A Novel Approach to Tokamak Magnet Material Development

Optimisation of REBCO coated conductor tapes specifically for use in nuclear fusion will help improve the magnet component lifetimes in future tokamak reactor power plants. The focus of this work was exploration of a novel approach to irradiation studies on REBCO tapes, utilising multiple magnetic measurements to probe evolution of the REBCO flux-pinning landscape more deeply than reported in other studies, for the purpose of identifying primary limiting factors affecting performance. Gamma irradiation experiments were conducted, and pre-/post-irradiation results from DC and AC magnetic measurements using a Physical Property Measurement System (PPMS) are discussed. Magnetisation critical current density (Jc) decreased in all samples with increasing dose, except for the silver overlayer-only samples which did not contain artificial pinning centres (APCs), where Jc increased with dose. Removal of the copper stabiliser coupled with the presence of APCs allowed gamma irradiation to induce pinning force maximum peak shifts, from above 14 T before irradiation to below 9 T afterwards. Flux creep rate varied with the evolving pinning landscape, and the degree of Jc degradation directly correlated with creep rate fluctuations post-irradiation. Changes in critical temperature and diamagnetic saturation also corresponded with changes in Jc and flux creep rate. The major conclusion from this study was that minimisation of flux creep rate is the key to maintenance of performance under fusion-relevant operating conditions. Flux creep manifests as problematic AC losses in all high-temperature superconducting machines; therefore, future work will focus on reduction/prevention of the phenomenon to enhance longevity of performance in any application.

Thermodynamic data of a promising cathode material NaV6O15 and its synthesis/decomposition thermodynamic analysis

Sodium-ion batteries have emerged as a promising alternative to lithium-ion batteries due to their lower cost and similar electrochemical properties. The development of high-capacity and long-life electrode materials is crucial for advancing sodium-ion battery research. A significant amount of research has been conducted on the electrochemical properties of NaV6O15, however, there remains a dearth of data on its thermodynamic properties. Herein, NaV6O15 was synthesized using the solid-phase sintering method and thoroughly characterized. Thermodynamic data in the temperature ranges of 298.15–900 K, 15–303 K, and 573–873 K were determined using the Neumann-Kopp rule, low-temperature physical property measurement system, and MHTC 96 line, respectively. The heat capacity equation of NaV6O15 was derived and its enthalpy, entropy, and Gibbs free energy (298.15–800 K) were calculated. Moreover, the thermodynamics of NaV6O15-related formation and decomposition reactions were analyzed. The obtained heat capacity equation of NaV6O15 was Cp=517.05524+0.08612T−1.25053×107T−2(J/mol·K)(298.15∼873K). This study addresses the thermodynamic knowledge gaps of NaV6O15 and provides valuable insights for its preparation and decomposition in manufacturing processes.

Study on the welding properties of modified N50 CICC jacket for future fusion applications

The modified N50 (N50H) cable-in-conduit conductor CICC jacket developed by China will be applied in China Fusion Engineering Test Reactor (CFETR). Building upon the N50H material, China has developed a corresponding welding material and conducted R&D work on N50H jacket welding. We simulated the N50H jacket welded joint to replicate the entire process of CICC preparation, which includes extrusion, bending, straightening and aging. The magnetic properties of welded joints were evaluated at various temperatures using a physical property measurement system. In addition, the microstructure of the welded joint was studied by various microscopic analysis techniques, and the welded joint showed a stable austenitic structure. Furthermore, mechanical properties of the welded joints were investigated at different temperatures with particular emphasis on their behavior at 4.2 K. The circle-in-square ReBCO conductor jackets welding joint showed a yield strength greater than 1500 MPa, a fracture toughness KIC better than 260 MPa m1/2 and the elongation at break is more than 30 % at 4.2 K. However, a decrease in strength, ductility, and fracture toughness is observed within the welded joints of Nb3Sn conductor jackets after undergoing an aging process. This study will present experimental data on welding joints and discuss the feasibility of N50H as a high-magnetic field jacket material for next-generation fusion reactors.