Critical Current Research Articles

Constructing Ionic Interfaces for Stable Electrochemical CO2 Reduction.

The electrochemical CO2 reduction reaction (CO2RR) has emerged as a promising approach for sustainable carbon cycling and valuable chemical production. Various methods and strategies have been explored to boost CO2RR performance. One of the most promising strategies includes the construction of stable ionic interfaces on metallic or molecular catalysts using organic or inorganic cations, which has demonstrated a significant improvement in catalytic performance. The stable ionic interface is instrumental in adjusting adsorption behavior, influencing reactive intermediates, facilitating mass transportation, and suppressing the hydrogen evolution reaction, particularly under acidic conditions. In this Perspective, we provide an overview of the recent advancements in building ionic interfaces in the electrocatalytic process and discuss the application of this strategy to improve the CO2RR performance of metallic and molecular catalysts. We aim to convey the future trends and opportunities in creating ionic interfaces to further enhance carbon utilization efficiency and the productivity of CO2RR products. The emphasis of this Perspective lies in the pivotal role of ionic interfaces in catalysis, providing a valuable reference for future research in this critical field.

DTT toroidal field conductor samples test in sultan: DC and AC characterization

Abstract The superconducting magnet system of the Divertor Tokamak Test (DTT) facility, composed of 18 Toroidal Field (TF) coils, 6 Poloidal Field (PF) coils and a Central Solenoid (CS), has been designed and many procurements have been launched. Some manufacturing aspects and some conductor features require characterization under relevant close-to-operative conditions. To confirm the design choices in all details, cryogenic tests in qualified facilities have been foreseen. In this work, the results of the TF samples characterization at the SULTAN facility at the Swiss Plasma Centre (SPC, EPFL) are presented. The 3 weeks test campaign started on July the 8th, 2022. The DTT TF SULTAN sample was made of two Nb3Sn Cable-in-Conduit conductor “legs”, namely “TF-A” and “TF-B”, made with wires produced by Kiswire Advanced Technology (KAT), differing for the cabling twist pitch sequence only, and designed to work in DTT at 42.5 kA at 11.9 T peak field.
The extensive characterization comprised 3000 Electro-Magnetic (EM) cycles and two Warm-Up-Cool-Down (WUCD) steps, and in detail it included: AC measurements on the virgin conductors, on cyclic loaded conductors and after WUCDs; DC tests at 10.85 T / 42.5 kA with intermediate electro-magnetic (EM) cycles at 10.85 T / 45 kA before and after WUCDs; DC tests using partial Lorentz force loads, and Minimum Quench Energy (MQE) tests at 9 T / 42.5 kA after cycles and WUCDs. The results of the DC measurements analysis verified the design, in terms of current sharing temperature (Tcs) and critical current (Ic), as both samples are over the minimum acceptance values. In particular, the “TF-A” sample, characterized by a so-called “long twist pitch” cabling sequence, showed higher performance without any degradation with loading and WUCD cycles, whereas sample “TF-B” presented an initial Tcs reduction that afterwards substantially remained unchanged. In terms of strain acting at the Nb3Sn filaments level, this result can be described by a lower effective strain in the “TF-A” sample. AC losses were measured with a calorimetric method as a function of frequency for each series of AC sinusoidal pulsing measurements, and the characteristic coupling time constants were determined.

Electrical detachment of triboelectrically charged bumpy particles from rough surfaces

The detachment of bumpy particles from smooth and rough surfaces through electrostatic fields was studied. The Johnson–Kendall–Roberts (JKR) adhesion model for elastic interface deformations was used to account for the individual bump adhesion, including the electrostatic forces. It was assumed that the elastic deformation of asperities determines the real contact area, and the effect of topographic properties of substrates was included in the analysis. For a fixed charge per unit mass, the Coulomb, the image, the dielectrophoretic, and the polarization forces acting on the particle in the presence of an imposed electric field were evaluated. The electrostatic detachment of bumpy toner particles for various applied electrostatic fields was studied. The triboelectric charges were concentrated on the hemispherical bumps, and the critical electric field strength needed to detach charged particles from surfaces with varying roughness levels was evaluated. It was shown that the particle charge, surface roughness, and the number of bumps significantly affect the removal of particles from surfaces. For higher charges (∼5 × 10−15 C ), decreasing the number of bumps from 22 to 14 and the roughness parameter from 0.83 to 0.77 approximately doubled the detachment field needed to remove 8.3 μ m polystyrene (PSL) particles from the aluminum oxide substrate. The model predictions are compared with the available experimental data, and good agreement was observed. The study’s findings predicting the electric field needed for charged particle removal could lead to more efficient copiers and electrostatic cleaning devices.

The Specificity of Fantasy and the “Affective Novum”: A Theory of a Core Subset of Fantasy Literature

This article proposes a new approach to the nature of a core set within fantasy fiction that regards it as a speculative literature of the exploration of subjectivity, one which at its limit conjectures fresh possibilities for the subjective world. To motivate acceptance of this proposed approach, I begin by surveying the existing state of debate in the critical field. I notice the emergence of widening agreement on the idea that fantasy is a literature of the impossible. I then develop the logical implications of this widening agreement in the critical field, arguing that it entails a representational definition of fantasy literature, which implies a modal approach to the core set that defines this literary order. I suggest that the marvellous mode, the kind of writing which represents the impossible, is a broad class that includes other speculative literatures, and that what differentiates these is the referential world within which the impossible happens. The aim here is to break up monolithic conceptions of the impossible, while pointing to a motivation for developing an understanding of the specificity of a core set of fantasy texts that proceeds by way of contrasts. After explaining why I am extremely skeptical about the definition of science fiction as a “literature of the possible”, I probe descriptions of the difference between fantasy and sci-fi. I propose that whereas some science fiction is a literature of conjectural objectivity, guided by the “cognitive novum”, a significant group of fantasy texts is a literature of speculative subjectivity, guided by an “affective novum”.

Thermal and electric field driven rf breakdown precursor formation on metal surfaces

The phenomenon of electric breakdown poses serious challenges to the design of devices that operate in high electric field environments. Experimental evidence points toward breakdown events that are accompanied by elevated temperatures and dark current spikes, which is attributed to high-asperity nanostructure formation that enhances the local electric field and triggers a runaway process. However, the exact mechanistic origin of such nanostructures under typical macroscopic operational conditions of electric field and magnetic-field-mediated heating remains poorly understood. In this work, we simulate the evolution of a copper surface under the combined action of the electric fields and elevated temperatures. Using a mesoscale curvature-driven surface evolution model, we show how a copper surface can undergo a type of dynamical instability that naturally leads to the formation of sharp asperities in realistic experimental conditions. Exploring the combined effect of fields and temperature rise, we identify the critical regimes that allow for the formation of breakdown precursors. The results show that thermoelastic stresses, while not essential, can significantly lower the critical electric field required for runaway surface instability, which is consistent with experimental observations that thermal effects can increase breakdown rates. Published by the American Physical Society 2024

Numerical solutions to hyperbolic Maxwell quasi-variational inequalities in Bean-Kim model for type-II superconductivity

This paper is devoted to the finite element analysis for the Bean-Kim model governed by the full 3D Maxwell equations. Describing type-II superconductivity at the macroscopic level, this model leads to a challenging coupled system consisting of the Faraday equation and a hyperbolic quasi-variational inequality (QVI) of the second kind with $L^1$-type nonlinearity, that arises explicitly from the magnetic field dependency in the critical current. With the involved Maxwell coupling in the 3D $\H(\curl)$-setting, the hyperbolic QVI character poses the primary challenge in the numerical investigation. Two mixed finite element methods based on implicit Euler and leapfrog time-stepping are proposed. On the one hand, the implicit Euler method results in a nonstandard system of curl-curl elliptic QVI with a first-order curl-type nonlinearity. Though the well-posedness of this system is guaranteed, its numerical realization is not straightforward and requires the use of a two-stage iteration process of high computational complexity. On the other hand, by approximating the electric and magnetic fields at two different time step levels, the leapfrog method turns out to be more suitable as it naturally eliminates the notorious QVI structure. More importantly, utilizing suited subdifferential and optimization techniques, we are able to prove an efficiently computable explicit formula for its exact solution in terms of the electric field, which makes its numerical computation substantially more favorable than the Euler method. As further advantages, the leapfrog method applies to broad scenarios involving low regular data of bounded variation (BV) in time for both the applied current source and the temperature distribution. Through nonstandard technical arguments tailored to the BV data, our analysis proves the conditional stability and, eventually, the uniform convergence of the proposed leapfrog method. This paper is closed by 3D numerical tests showcasing the reasonable and efficient performance of the proposed numerical solution.

Development of Arabic Language Curriculum Focused on Diversity and Inclusion

This literature review explores the development of an Arabic language curriculum prioritizing diversity and inclusion in an interconnected global context. It aims to formulate a curriculum catering to learners from diverse cultural backgrounds, abilities, and learning preferences, ensuring fair access and meaningful engagement. The methodology involves an extensive literature review, expert consultations, and data collection through surveys, interviews, and focus group discussions. Thematic coding and triangulation facilitate data analysis, revealing the importance of integrating diverse perspectives and inclusive pedagogical approaches. The study emphasizes nurturing an inclusive learning environment that embraces differences and fosters mutual respect. It highlights implications for educators, curriculum developers, and policymakers, stressing deliberate efforts to address diversity and inclusion within Arabic language education. Inclusive practices can effectively address diverse learner needs, promote cross-cultural understanding, and cultivate belonging. This research advances inclusive language education and encourages further exploration in this critical field.

Penetration depth and critical fields in superconducting NbTi thin films grown by co-sputtering at room temperature

We present a study on the superconducting properties of 300 nm thick NbTi thin films grown by co-sputtering on silicon substrates at room temperature. The samples exhibit a Nb (50 at%) and Ti (50 at%) chemical composition, revealing a polycrystalline structure textured along the (110) axis of the body-centered cubic structure. The measured superconducting critical temperature (T c ) was 9.65 K, and the upper critical field extrapolated to zero temperature reached approximately 15 T, resulting in a coherence length at zero temperature of approximately 4.7 nm. The penetration depth was determined through local magnetic force microscopy measurements conducted at temperatures from 4.25 to 7 K. The obtained values range from (250 ± 15) nm at 4.25 K to (370 ± 20) nm at 7 K. Extrapolating these measurements to zero temperature, we obtained an estimated value of (230 ± 20) nm. To extend the performance and potential applications of NbTi, we additionally grew a 150 nm thick sample on flexible polyimide. In this case, we observed that the films preserved their superconducting properties, displaying a decrease in T c to 9.2 K and a similar upper critical field compared to samples grown on silicon. The feasibility of growing NbTi alloys at room temperature, with superconducting parameters comparable to or superior to metallic Nb for the upper critical field, renders this system promising for cryogenic applications, particularly in the development of high-performance electronic devices on both rigid and flexible substrates.

Predicting Drug Resistance in Gastric Cancer with Mutation in the Human Epidermal Growth Factor Receptor 2 (HER2) And Machine Learning Technique

Gastric cancer with mutations in the human epidermal growth factor receptor (HER2) can be regarded as one of the leading causes of cancer mortality in the world. Targeted tyrosine kinase inhibitors (TKIs) developed against HER2 yielded optimistic results in improving patients' survival rates and life quality. Nevertheless, drug resistance can influence the critical supportive documents of treatment plans and decrease the treatment effectiveness after about one year. Predicting the efficacy of HER2-TKI drugs or therapies for patients with HER2-mutated gastric cancer is a critical research field. In the present study, a personalized drug response prediction model based on molecular dynamics simulations and machine learning is presented to predict response to first-generation drugs approved by the Ministry of Health in patients with gastric cancer. In the molecular dynamics simulation, the patient's mutation status is considered. The patient's unique mutation status was modeled using molecular dynamics simulations to extract geometric features at the molecular level.Furthermore, additional clinical features are incorporated into the machine learning model to predict drug response. The complete features encompass demographic and clinical characteristics, geometrical properties of the drug-target binding site, and binding free energy (RBFE) of the drug-target complex from molecular dynamics simulations. Drug response prediction utilizes the XGBoost classifier, which achieved leading-edge performance for a 4-level drug response prediction task (PDRP) with 97.5% accuracy, 93% sensitivity, 96.5% specificity, and 94% F1 score. The present research has demonstrated that modeling the binding cavity geometry, in tandem with the binding free energy, can effectively predict drug response. Interestingly, the clinical information, while significant, did not significantly influence the model's performance. This exciting finding opens up new avenues for testing the proposed model on various types of cancers, potentially revolutionizing drug development strategies. DOI: https://doi.org/10.52783/pst.391

Investigating the neurobiology of maternal opioid use disorder and prenatal opioid exposure using brain organoid technology

Over the past two decades, Opioid Use Disorder (OUD) among pregnant women has become a major global public health concern. OUD has been characterized as a problematic pattern of opioid use despite adverse physical, psychological, behavioral, and or social consequences. Due to the relapsing–remitting nature of this disorder, pregnant mothers are chronically exposed to exogenous opioids, resulting in adverse neurological and neuropsychiatric outcomes. Collateral fetal exposure to opioids also precipitates severe neurodevelopmental and neurocognitive sequelae. At present, much of what is known regarding the neurobiological consequences of OUD and prenatal opioid exposure (POE) has been derived from preclinical studies in animal models and postnatal or postmortem investigations in humans. However, species-specific differences in brain development, variations in subject age/health/background, and disparities in sample collection or storage have complicated the interpretation of findings produced by these explorations. The ethical or logistical inaccessibility of human fetal brain tissue has also limited direct examinations of prenatal drug effects. To circumvent these confounding factors, recent groups have begun employing induced pluripotent stem cell (iPSC)-derived brain organoid technology, which provides access to key aspects of cellular and molecular brain development, structure, and function in vitro. In this review, we endeavor to encapsulate the advancements in brain organoid culture that have enabled scientists to model and dissect the neural underpinnings and effects of OUD and POE. We hope not only to emphasize the utility of brain organoids for investigating these conditions, but also to highlight opportunities for further technical and conceptual progress. Although the application of brain organoids to this critical field of research is still in its nascent stages, understanding the neurobiology of OUD and POE via this modality will provide critical insights for improving maternal and fetal outcomes.

Fabrication of planar halfmetallic ferromagnetic Josephson junctions with long range coupling

Superconducting junctions with a ferromagnet as the weak link, where triplet correlations can transport supercurrents over a substantial distance, have been of long-standing interest. In this work, we study the triplet transport in planar La0.7Sr0.3MnO3 (LSMO) nanowire Josephson junctions with NbTi superconducting contacts. By meticulous ion etching with an artificial Pt hard mask, the NbTi/LSMO bilayer is structured to form an LSMO bridge without damaging its top layer. We observe superconducting (critical) currents of the order of 109 A/m2 in a junction with a length of 1.3 μm, and distinguishing superconducting quantum interference (SQI) patterns when sweeping a magnetic field perpendicular (B⊥) to the plane of the wire or parallel (B∥) to the plane and along the wire. The observed Gaussian-shaped SQI pattern is attributed to the diffusive transport of triplet pairs in the LSMO. Our work demonstrates that combinations of oxide magnets with conventional (s-wave) alloy superconductors can be a promising new route to realizing superconducting spintronics.

Recent Advanced Ultra‐Wide Bandgap β‐Ga2O3 Material and Device Technologies

AbstractGallium oxide (Ga2O3) is an emerging ultra‐wide bandgap (UWBG) semiconductor material that has gained significant attention in the field of high voltage and high frequency power electronics. Its noteworthy attributes include a large bandgap (Eg) of 4.8 eV, high theoretical critical breakdown field strength (EC) of 8 MV cm−1, and saturation velocity (νs) of 2 × 107 cm s−1, as well as high Baliga figures of merit (BFOM) of 3000. In addition, Ga2O3 has the advantages of large‐size substrates that can be achieved by low‐cost melt‐grown techniques. This review provides a partial overview of pivotal milestones and recent advancements in the Ga2O3 material growth and device performance. It begins with a discussion of the fundamental material properties of Ga2O3, followed by a description of substrate growth and epitaxial techniques for Ga2O3. Subsequently, the contact technologies between Ga2O3 and other materials are fully elucidated. Moreover, this article also culminates with a detailed analysis of Ga2O3‐based high voltage and high frequency power devices. Some challenges and solutions, such as the lack of p‐type doping, low thermal conductivity, and low mobility are also presented and investigated in this review.

A newly developed 10 kA-level HTS conductor: innovative tenon-mortise-based modularized conductor (TMMC) based on China ancient architecture

We proposed a new type of high-temperature superconducting (HTS) conductor concept: modularized conductors (MCs) connected by Chinese traditional tenon-mortise (TM) connection structure, referred as TMMC (tenon-mortise modularized conductor). The conductor consisted of multiple concentric round sub-conductors with slots for stacking rare-earth-barium-copper-oxide (REBCO) tapes. Innovatively, the REBCO stacks in the adjacent sub-conductors were arranged with the fully-misaligned configuration to enhance the critical current’s isotropy with respect to magnetic field and reduce ac loss. For example, the angle between the adjacent stacks in the two adjacent sub-conductors was 45° if each sub-conductor contains 4 REBCO stacks. In order to construct the fully-misaligned configuration, the sub-conductors were designed with two open half-circular formers and connected by TM structure which makes the conductor modularized and simply to assembly and disassembly. Based on the design concept, a prototype conductor containing 160 REBCO tapes distributed in the four concentric sub-conductors was fabricated. The conductor’s measured critical current was 13.69 kA at 77 K and self-field, which was consistent to the simulation result. In order to further improve the TMMC’s engineering critical current density (J ce) and bending performance, we proposed two enhancement approaches: reducing the former’s thickness and re-arrange stacks in the outer sub-conductors. With the enhancements, both TMMC’s radius and J ce were comparable to the existing slotted-core conductor. The study shows the TMMC’s advantages of non-twisted structures, easy assembly, high-current carrying and low ac losses, which made it promising for constructing large-scale scientific devices.

Shaping the Future of Environmental Economics: A Bibliometric Review of Current Trends and Future Directions

Environmental economics is increasingly pivotal in addressing global environmental challenges. This study aims to elucidate the research landscape in this field, focusing on prevalent themes such as climate change, carbon emissions, sustainable development, and environmental policy. Employing a bibliometric analysis, we analyzed a substantial corpus of literature from Scopus. We applied Lotka's Law to assess author productivity and distribution and conducted institutional and country-level analyses to map the geographical spread and institutional affiliations in environmental economics research. Our analysis highlights a significant growth in the environmental economics literature, with a notable focus on climate change and sustainability. A concentration of publications among a few authors was observed, indicating influential researchers and potential for increased collaboration. The rise in publications, particularly in China and leading journals like 'The Journal of Cleaner Production,' reflects a global upsurge in environmental economics research. Distinct clusters were identified, covering diverse topics from climate change economics to environmental policy. The study acknowledges limitations due to exclusive reliance on Scopus data, suggesting future research to include other databases like the Web of Science for a more comprehensive analysis. Considering the evolving nature of environmental challenges, we advocate for interdisciplinary approaches and continual updates in research to address emergent trends in this critical field.

Superior Superconducting Properties Realized in Quaternary La-Y-Ce Hydrides at Moderate Pressures.

The recent revolution in the superconductivity field stems from hydride superconductors. Multicomponent hydrides provide a crucial platform for tracking high-temperature superconductors. Besides high superconducting transition temperature (Tc), achieving both giant upper critical magnetic field [μ0Hc2(0)] and high critical current density [Jc(0)] is also key to the latent potential of the application for hydride superconductors. In this work, we have successfully synthesized quaternary La-Y-Ce hydrides with excellent properties under moderate pressure by using the concept of "entropy engineering." The obtained temperature dependence of the resistance provides evidence for the superconductivity of Fm3m-(La,Y,Ce)H10, with the maximum Tc ∼ 190 K (at 112 GPa). Notably, Fm3m-(La,Y,Ce)H10 boasts exceptional properties: μ0Hc2(0) reaching 292 T and Jc(0) surpassing 4.61 × 107 A/cm2. Compared with the binary LaH10/YH10, we find that the Fm3m structure in (La,Y,Ce)H10 can be stable at relatively low pressures (112 GPa). These results indicate that multicomponent hydrides can significantly enhance the superconducting properties and regulate stabilizing pressure through the application of "entropy engineering." This work stimulates the experimental exploration of multihydride superconductors and also provides a reference for the search of room-temperature superconductors in more diversified hydride materials in the future.

Structural and superconducting properties in the Te-doped spinel CuRh2Se4

In this paper, we discuss the impact of tellurium (Te) doping on the spinel superconductor CuRh2Se4. We conducted a comprehensive evaluation of the structural and superconducting properties of the system using various techniques, including X-ray diffraction (XRD), resistivity, magnetization, and specific heat measurements. Based on our XRD analysis, we found that the spinel superconductor CuRh2Se4-xTex (0 ≤ x ≤ 0.28) crystallizes in the space group Fd3̅m (227), while the layered compound CuRh2Se4-xTex (2.8 ≤ x ≤ 4.0) crystallizes in the space group P3̅m1 (164). The upper critical magnetic field can be increased from 0.95(2) T for CuRh2Se4 to 3.44(1) T for CuRh2Se3.72Te0.28 by doping with elemental Te. However, the layered compound CuRh2Se4-xTex (2.8 ≤ x ≤ 4.0) did not exhibit superconducting properties. Besides, the specific heat measurements of CuRh2Se4-xTex (x = 0, 0.1, 0.28) indicate that the Te element doping affects the electronic structure and interactions of the material and breaks the stability of the superconducting pairing, which leads to a decrease in the Tc. Finally, we show the electronic phase diagram of Tc with Te doping to summarise our findings.

Damage recovery for SRF photoinjector cavities

Two niobium elliptical 1.3 GHz superconducting radio frequency (SRF) electron photoinjector cavities were successfully recovered after mechanical inner surface damage. Both cavities had deep imprints in the critical high surface electric field area around the photoelectric cathode position. The lengthy repair procedure, which consists of surface inspection and defect characterization, mechanical polishing and light chemical etching is described in detail. In the process, a new high pressure rinsing (HPR) nozzle system optimized for the special photoinjector geometry was also developed. Subsequent cold RF tests demonstrate complete performance recovery. This is the first time that photoinjector cavities damaged in the high electric-field region could be recovered.

Superconductivity with a high upper critical field in an equiatomic high-entropy alloy Sc–V–Ti–Hf–Nb

High-entropy alloy (HEA) superconductors have attracted significant attention due to their exceptional low-temperature mechanical and superconducting properties. We report the synthesis and thorough characterization of an equiatomic HEA superconductor with the composition Sc0.20V0.20Ti0.20Hf0.20Nb0.20, crystallizing in a body-centered cubic crystal structure (Im3m¯). Our investigation, using magnetization, transport, and heat capacity measurements, reveals the presence of weakly coupled, fully gapped superconductivity with a transition temperature of 4.17(3) K and the upper critical field exceeding the Pauli paramagnetic limit. The metallic nature, combined with a high upper critical field, positions it as a promising candidate for applications in superconducting devices.

Queer theory impossible

ABSTRACT This essay examines the institutional construction of “queer theory” as a field in the United States and its translation and subsequent failure outside the U.S. Despite presenting itself as a critical field of inquiry, queer theory has been centered in the most privileged institutions in the global North, primarily in the U.S. I investigate how U.S.-centric queer theory has built upon the international division between “theory” and “case,” rooted in colonial science and knowledge production, particularly in relation to sexuality and race. To address these issues, I analyze the controversy surrounding the publication and translation of the edited volume, Queer Korea, from Duke University Press’s acclaimed Perverse Modernities series, focusing on research ethics and hegemonic whiteness. I argue that this controversy demonstrates how contemporary U.S.-centric queer theory appropriates and capitalizes on the language of “decentering,” “provincializing,” or “decolonizing” at the expense of marginalized queer lives, struggles, and knowledge outside the U.S.

Antiferromagnetic ground state and evidence for metamagnetic transition in itinerant-electron compounds YCo12−xFexB6 (x = 1.5, 2, 2.5)

In contrast to the parent compound YCo12B6, the Fe-doped YCo12−xFexB6 (1.5 ≤ x ≤ 2.5) alloys exhibit an antiferromagnetic ground state. It is further revealed that the antiferromagnetic state gets transformed into a forced ferromagnetic state by way of a magnetic-field-induced metamagnetic transition. The results demonstrate a progressive reinforcement of the antiferromagnetic interactions upon increasing Fe content along the YCo12−xFexB6 series of compounds. The magnetic phase diagram of each (x = 1.5, 2, and 2.5) composition is determined by combining isothermal and isofield magnetization measurements. The composition and temperature dependencies of the critical field are derived and discussed. Whereas for x = 2 and 2.5, the magnetic state changes from antiferromagnetic (AFM) to ferromagnetic (FM) and then to the paramagnetic (PM) state upon heating, exhibiting three distinct temperature regions, a multicritical point of magnetic origin is proposed for the x = 1.5 compound at a temperature of about 117 K. The ordering temperature is found to decrease upon increasing Fe concentration, while the critical field of the AFM-FM metamagnetic phase transition shows the opposite trend. The critical transition field diminishes upon increasing temperature.