High-temperature Magnetization Research Articles

Enhanced visualization of quench dynamics of HTS coils through embedded and distributed fiber optical sensing

The development of high-temperature superconducting (HTS) coils and magnets marks a significant advancement across various fields. To ensure their safety and reliability, thorough performance testing under extreme multi-field conditions is essential. This study introduces an innovative method that utilizes embedded and distributed fiber optical sensing (ED-FOS) in HTS pancake coils for precise real-time thermal monitoring and quench visualization. Incorporated during the manufacturing process, the ED-FOS sensors offer comprehensive and distributed measurements of thermal behavior during quenches. Our experiments demonstrate the ED-FOS effectively detects quenches caused by overcurrent and thermal issues. Unlike conventional techniques that rely on global voltage or magnetic field assessments, ED-FOS provides high spatiotemporal resolution and enhances temperature sensitivity. This capability allows for accurate, real-time identification and tracking of quench locations, which is essential for evaluating reliability and safety, as well as for improving performance. This advancement in HTS coil technology paves the way for wider application in critical fields and significantly enhances the design and management of superconducting coils.

High Entropy Protected Sharp Magnetic Transitions in Highly Disordered Spinel Ferrites.

How disorder affects magnetic ordering is always an intriguing question, and it becomes even more interesting in the recently rising high entropy oxides due to the extremely high disorder density. However, due to the lack of high-quality single crystal samples, the strong compositional disorder effect on magnetic transition has not been deeply investigated. In this work, we have successfully synthesized high-quality single crystalline high entropy spinel ferrites (Mg0.2Mn0.2Fe0.2Co0.2Ni0.2)xFe3-xO4. Our findings from high-temperature magnetization and neutron diffraction experiments showed ferrimagnetic transitions at 748, 694, and 674 K for x values of 1, 1.5, and 1.8, respectively. Notably, the magnetic transition almost showed no broadening for x values of 1 and 1.5, compared to Fe3O4. Extended X-ray absorption fine structure measurements provided insights into the elemental distribution among the octahedral and tetrahedral sites. The random distribution of elements across these sites reduced the formation of local clusters and short-range orders, enhancing sample homogeneity and preserving the sharpness of the magnetic transition, despite bond length variation. Our study not only marks the first successful synthesis of an HEO bulk single crystal exhibiting long-range magnetic order but also sheds light on the interaction between high configurational entropy and magnetic orderings. This opens new avenues for future research and applications of magnetic high entropy oxides.

Model simulation analysis of superconducting switch applied to high-temperature superconducting electromagnetic suspension magnet

This paper presents a simulation analysis of the switching characteristics of a thermal control superconducting switch used in high overload electromagnetic suspension trains. A two-dimensional axisymmetric model was established using superconducting tape encapsulated in non-copper-plated stainless steel. Simulation analysis of thermal control switch heating and quenching was performed in the absence of an external magnetic field. The simulation results show that the switching resistance is 4.

Transient thermal analysis model of nitrogen-cooled cryogenic system for superconducting electromagnetic suspension magnet

This paper proposes a transient thermal analysis model for a nitrogen-cooled cryogenic system used in superconducting electromagnetic suspension magnets. First, the structural parameters of the nitrogen cryogenic system and the internal high-temperature superconducting magnet are detailed. Subsequently, temperature change simulations during the system's cooling process using a cryocooler, as well as during the cooling and nitrogen-insulation process, were conducted using COMSOL software. Finally, simulations of the temperature variations during the system's offline operation were performed. This study provides valuable references for the design and optimization of nitrogen-cooled cryogenic systems.

Pushing magnetic spirals beyond room temperature by reducing the uniaxial pyramidal elongation in layered Cu/Fe perovskites

The impact of a 3d divalent substitution for Cu using M2+ ions not presenting elongated MO5 pyramids has been explored in YBaCuFeO5 as a new strategy to upgrade the magnetic properties of this high-temperature spiral magnet and potential multiferroic. In this work we investigate the incidence of the Cu2+ with Co2+ substitution in YBa(Cu1−xCox)FeO5 compounds in which B-site disorder is kept invariant (disorder nd≈36%). The study validates the reduction of the uniaxial elongation distortion at Cu sites as an efficient alternative way to disorder that enables one to enhance the thermal stability of the spiral order. In addition, the rotation plane of the helix is reoriented by the Cu/Co substitution and nearby the triple point (when TS is maximal) the spiral order adopts an almost complete cycloidal magnetic configuration. These results lay the foundation of a new mechanism to tune the stability of the magnetic spirals in layered perovskites based on reducing the uniaxial elongation associated to the (4+1)-coordination of Cu2+ ions in square CuO5 pyramids. Published by the American Physical Society 2024

A platform to study defect-induced behavior in high-temperature superconductor cables

High-temperature superconductor (HTS) cables and magnets are enabling a range of high-current and high-field applications, including compact fusion devices aiming to achieve net energy. Defects in HTS pose manufacturing, cost, and operational challenges. A rigorous understanding and predictive capability for defect-induced behavior at relevant scale has not been established. To address this shortcoming, we have developed a cable-level defect characterization experimental platform coupled to high-fidelity computational modeling. The cable ( Ic∼ 438 A at 77.4 K, self-field) comprises a non-twisted 70 cm-long copper former containing a soldered stack of five rare-earth barium copper oxide (REBCO) tapes (each with Ic = 115.7 A/4 mm-w at 77.4 K, self-field), which can contain a variety of induced defects. Spatially-resolved electric fields are measured with a high-density voltage tap array and absolute current distribution with six custom-wound embedded Rogowski coils. 3D circuit modeling uses nodal analysis and self-consistently accounts for the magnetic field dependence of critical current. The model successfully predicts the experimentally measured spatial and operating current dependencies of electric field and current distribution with no defects, one defect, and two defects, validating the defect characterization platform as a tool for improving the design, cost, fabrication, and operation of REBCO cables.

Strong spin-phonon coupling in two-dimensional monolayer VS2 and the origin of its high-temperature magnetism

Exploring intrinsic two-dimensional (2D) ferromagnetic (FM) semiconductors with high Curie temperatures (T c) is an ongoing challenge. Herein, we found that the phonons of monolayer H-VS2 are strongly coupled to the magnetic ordering with the spin-phonon coupling constants (15.80 cm−1 for A1g and 78.72 cm−1 for E2g1 ) an order of magnitude larger than most other 2D materials, which restricts structural reconstruction of FM ground state through spin interactions. Based on anharmonic model, the variation trend of phonon energy with temperature clearly demonstrates FM ground state at room temperature. The theoretically predicted high T c of 303 K, closely in line with experimental observations, is correlated to the three lowest d-orbitals (i.e. dxy , dz2 and dx2−y2 ) split by the unique crystal field. The proximity of their energy levels facilitates efficient mutual virtual exchanges, which greatly prompts superexchange-driven FM coupling of adjacent spins, as confirmed by their orbital-resolved magnetic exchange coefficients. Our work validates the double-orbital model for the magnetic coupling mechanisms in 2D H-VS2, offers potentials to create novel high T c spintronic semiconductors and paves a way for design of complex micro/nano-magnetoelectric devices.

Monolayer Fe3GaX2 (X = I, Br, Sb): High-Temperature Two-Dimensional Magnets and a Novel Partially Ordered Spin State

Monolayer Fe₃GaX₂ (X = I, Br, Sb): High-Temperature Two-Dimensional Magnets and a Novel Partially Ordered Spin State

Development of High-Temperature Permanent Magnet Synchronous Motor for Autonomous Robotic Navigation: A Design and Finite Element Analysis Approach

The traditional industrial robots come with the prime mover, i.e. Electric Motors (EM) which ranges from a few hundred too few kilo watts of power ratings. However, for autonomous robotic navigation systems, we require motors which are light weighted with the aspect of high torque and power density. This aspect is very critical, when the EMs in robotic navigations are subjected to harsh high temperature survival conditions, where the sustainability of the performance metrics of the electromagnetic system of the EMs degrade with the prevailing high temperature conditions. Hence, this research work address and formulate the design methodology to develop a 630 W High Temperature PMSM (HTPMSM) in the aspect of high torque and power density, which can be used for the autonomous robotic navigation systems under high temperature survival conditions of 200°C. Two types of rotor configurations i.e. the Surface Permanent Magnet type (SPM) and the Interior Permanent Magnet type (IPM) of HTPMSM are examined for its optimal electromagnetic metrics under the temperature conditions of 200°C. The 630 W HTPMSM is designed to deliver the rated torque of 2 Nm within the volumetric & diametric constraints of D x L which comes at 80 x 70 mm at the rated speed of 3000 rpm with the survival temperature of 200°C with the target efficiency of greater than 90%. The FEM based results are validated through the hardware prototypes for both SPM and IPM types, and the results confirm the effectiveness of the proposed design methodology of HTPMSM for sustainable autonomous robotic navigation applications.

Induced Magnetization in Antiferromagnetic GdFeO3 by Nonmagnetic Titanium Substitution for Magnetic Switching and Storage Application

Room temperature ferromagnetism has been induced in antiferromagnetic GdFeO3 by substituting titanium at Gd site Gd1-xTixFeO3 (x=0.00 - 0.25). Perovskite GdFeO3 has been synthesized at lower temperature by chemical co-precipitation. Titanium substitution in gadolinium orthoferrite has transformed the perovskite phase to garnet phase confirmed by X-ray diffraction analysis. Tolerance factor of perovskite structure has been reduced from 0.81 to 0.78 for x=0.25 Ti substitution. Antiparallel G-type electron spins of GdFeO3 has been distorted by structural change induced due to titanium substitution. Ferromagnetism has been increased to 0.74 emu/g from 0.5 emu/g by titanium substitution. Retentivity and coercivity has been also increased from 0.005 emu/g to 0.28 emu/g and 27 Oe to 218 Oe respectively. The increase in magnitude of ferromagnetic transition with respect of temperature has been significantly observed by high temperature magnetization measurement. Present process is easy to induce room temperature ferromagnetism in antiferromagnetic GdFeO3 by distorting the structure at lower temperature by titanium substitution. The retentivity and coercivity produced at x=0.25 titanium substitution is useful for magnetic memory and switching application.

Paleomagnetic study of terrigenous rocks of the Uryuk Formation in the Southern Urals

In order to obtain new paleomagnetic data on Vendian rocks in the Southern Urals, we studied the high-temperature magnetization component in sandstones of the Uryuk Formation, the carrier of which is hematite. The distinguished hematite vector in the collection of samples differs from the previously obtained intermediate-, intermediate-high-temperature magnetization component of magnetite, which is part of the same rocks. The average directions of the hematite component of magnetization of the Uryuk Formation were compared with the average directions of the overlying Basu Formation. The metachrony of the magnetite component and the synchrony of the hematite component are suggested.

Stable quantum-correlated many-body states through engineered dissipation.

Engineered dissipative reservoirs have the potential to steer many-body quantum systems toward correlated steady states useful for quantum simulation of high-temperature superconductivity or quantum magnetism. Using up to 49 superconducting qubits, we prepared low-energy states of the transverse-field Ising model through coupling to dissipative auxiliary qubits. In one dimension, we observed long-range quantum correlations and a ground-state fidelity of 0.86 for 18 qubits at the critical point. In two dimensions, we found mutual information that extends beyond nearest neighbors. Lastly, by coupling the system to auxiliaries emulating reservoirs with different chemical potentials, we explored transport in the quantum Heisenberg model. Our results establish engineered dissipation as a scalable alternative to unitary evolution for preparing entangled many-body states on noisy quantum processors.

Nano FeCoNi-based high-entropy alloy for microwave absorbing with high magnetic loss and corrosion resistance

With the development of modern communication and military technology, the protection of electromagnetic wave pollution and radar stealth technology have been widely concerned. In this background, the magnetic metals were widely used due to the strong ferromagnetism, which can induce strong magnetic loss to the electromagnetic wave. However, it remains challenging to precisely control the wave-absorbing performance of individual magnetic metals, and there are issues with poor corrosion resistance and high temperature resistance. Therefore, the alloy powders based on Fe, Co, and Ni in this work were prepared by wet chemical method at room temperature. Different from most of the traditional powder metallurgy methods, the wet chemical method enables us to obtain binary, ternary and quaternary alloys with a nanometer-scale and uniform distribution, all products have a microscopic morphology of 300–500 nm spheres. The FeCoNi alloy powder shows an effective absorption band (RL<-10 dB) of 7 GHz in the high frequency electromagnetic wave range at an ultrathin thickness of 1.5 mm, which has a high temperature magnetism (Tc >900 K) and excellent corrosion resistance. Further doping of Cu to form a quaternary alloy can improve the corrosion resistance and maintain the original wave-absorbing properties, while doping of Mo and Sn can adjust the position of the effective absorption bandwidth.

Experimental study on the an-isotropic critical current of REBCO tape.

Superconducting magnets are widely used in nuclear fusion reactors, high-energy particle accelerators, steady-state high magnetic fields, etc. Higher magnetic fields and higher operating temperatures are two application trends. High temperature superconducting (HTS) materials are the only choice for high temperature and high field magnets in the future. The first- and second-generation HTS materials have a typical tape structure; their critical performance is magnetic field angle and temperature dependent. A new test facility is developed for an experimental study on the an-isotropic critical current. The field angle can be changed from 0° to 360° with a resolution of 1°. The rotation deviation angle is measured to be 0.2° when the upper part rotates 90°. The temperature can be changed from 4.2 to 80K. The temperature errors are ±50, ±80, and ±135 mK for 4.2-20, 20-40, and 40-80K, respectively. The angle dependence of critical current (Ic) of the tested rare-earth barium copper oxide tape within 0°-30° is strong. From 30° to 90°, the sample Ic almost does not change with the magnetic field angle. The implementation of the project will not only promote the structural optimization of HTS tapes but also promote the miniaturization and economical application of HTS magnets.

Nonlinear motion characteristics of the high-temperature superconducting levitation system with boundary crack

High-temperature superconducting levitation systems have nonlinear behaviors, such as the period-doubling bifurcation and chaotic vibration under external excitation, in connection with the nonlinear hysteresis interaction between the high-temperature superconductors (HTSC) and permanent magnet. The HTSC is a non-ideal type II superconductor in which the fracture is generated internally during manufacturing, and the material properties are brittle. The HTSC tends to crack under a strong magnetic field and electromagnetic force, and its internal defects are likely to cause structural damage with the variable Lorentz force. The fracture performance of the superconducting magnetic levitation system will affect the temperature variation of HTSC, in which the temperature is coupled with the internal electromagnetic force. In this paper, we analyze the fracture characteristics of the HTSC in nonlinear vibration with thermal effect. A superconducting magnetic levitation system model with boundary cracks is applied to study the coupling of multiple physical fields in dynamic processes. The Maxwell equation and superconducting electromagnetic constitutive equation are used to obtain the superconductor’s current density, and the temperature is calculated through the heat conduction equation. The superconducting magnetic flux flow and creep model is applied to analyze the magnetic flux motion inside the superconductors. We compare the superconducting levitation system’s electromagnetic force, temperature, and current density with four critical current densities. The numerical results show that the critical current density of superconductors significantly impacts bifurcation motion, and the temperature of the crack tip of the superconductors varies greatly during vibration, causing the superconductor to lose its superconductivity.

Cationic disorder: Governing the spin-insulatronic properties of nanocrystalline ZnFe2O4 thin films

Controlling cation order/disorder in spinel offers a highly effective means of tailoring material properties by modifying inter- and intra-sub-lattice ionic interactions. In this study, we conducted high-temperature magnetization measurements (300–1000 K) to determine average Curie temperatures (TC) for nanocrystalline ZnFe2O4 thin films. Thermodynamical stability of these films under extreme conditions was investigated by assessing lattice structures, oxygen vacancies, magnetization, and electric resistivity for spin-insulatronic applications. Reversible cation inversion via heat treatments (in-situ and ex-situ) yields tunable ferrimagnetic (FiM) order in ZnFe2O4, with TC ranging from 425 to 710 K. First-principles calculations highlight effective cation inversion mitigating magnetic frustration, promoting collinear FiM ordering, and elevating TC. Oxygen vacancies further reinforce ferrimagnetism, slightly reducing resistivity through the formation of Fe-3d gap states near the Fermi level. A proposed magnetic nanophase diagram elucidates dominant competing magnetic ground states (cluster spin-glassy state, FiM, and antiferromagnetic) with increasing growth temperature, fostering innovative homo-architectures from multiple ZnFe2O4 thin films with diverse functionalities.

Thermal runaway criterion as a basis for the protection of high-temperature superconductor magnets

High-temperature superconductor (HTS) based high-field magnet systems are essential for particle accelerators and fusion energy applications. Quench protection of such magnets is difficult owing to a slow quench propagation velocity in HTS. While in conventional NbTi and Nb3Sn-based magnets, a normal zone expands typically quickly, and the stored energy is dissipated across a large volume of the windings, a normal zone in an HTS magnet propagates slowly and, thus, can heat up quickly to high temperatures destroying the conductor. At the same time, growing experimental evidence suggests that HTS conductors can operate in a stable dissipative flux flow regime for a substantial range of operational currents before entering an irreversible thermal runaway. Therefore, a new protection paradigm for HTS magnets has emerged, aiming to prevent quenching, using advanced diagnostics to detect the dissipative regime onset. In the present paper, we propose a simple criterion for the thermal runaway in HTS conductors and calculate allowable temperature margins within which an HTS magnet can be operated safely. Outside of those temperature margins, a common quench integral approach may be used to estimate the upper boundary of the time margin for activating the protection system. We verify the applicability of our approach by comparing the calculated runaway conditions for a Bi-2223 conductor with the experimentally measured values. The thermal and time margins can define the quench protection system’s requirements for implementing the quench-avoiding protection paradigm.

High-temperature magnetization and bulk magnetostriction investigation of Ti and Nb addition to Fe70Co30 alloy

High-temperature magnetization and bulk magnetostriction investigation of Ti and Nb addition to Fe70Co30 alloy

Influence of weakly coordinating anions binding to the hexa-tert-butyl dysprosocenium cation.

Complexes containing isolated dysprosocenium cations, [Dy(CpR)2][WCA] (CpR = substituted cyclopentadienyl, WCA = weakly coordinating anion), have recently emerged as leading examples of high-temperature single-molecule magnets (SMMs) due to a combination of the axial orientation and rigidity of the CpR rings. However, our understanding of the effects of transverse fields on the magnetic properties of [Dy(CpR)2]+ cations is underdeveloped. Here we investigate the impact of equatorially-bound WCAs via the synthesis of the Dy(III) bis-CpR complexes [Dy(Cpttt)2{AlCl[OC(CF3)3]3-κ-Cl}] (1) and [Dy(Cpttt)2{AlCl(C2H5)[OC(C6F5)3]2-κ-Cl}] (2), and their characterisation by single crystal XRD, elemental analysis, ATR-IR and NMR spectroscopy, and ab initio calculations. Despite the similarity of the Dy coordination spheres in 1 and 2 we find that their effective energy barriers to reversal of magnetisation are vastly different (Ueff = 886(17) cm-1 and 559(18) cm-1, respectively) and they both show waist-restricted magnetic hysteresis at 2 K. Together, these data provide fresh insights into the sensitivity of the magnetic properties of [Dy(CpR)2]+ cations to relatively weak equatorial interactions.

Unravelling electronic structure, bonding and magnetic properties of inorganic dysprosocene analogues [Dy(E4)2]− (E= N, P, As, CH)

Organometallic sandwich complexes of Dy(III) ion are ubiquitous for designing high-temperature single-ion magnets with blocking temperatures close to the liquid nitrogen boiling point. Magnetic bistability at the molecular level makes...