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We investigate the magnetic, thermal, and magnetocaloric properties of the intermetallic HoAl$_{3}$ compounds with two different crystal structures. The room-temperature equilibrium trigonal phase HoAl$_{3}$ undergoes an antiferromagnetic (AFM) transition at the Neel temperature $T^{\rm tri}_{\rm N} =$ 9.8 K. The AFM ordering of the compound is strong against the magnetic field, so that inverse magnetocaloric effect (MCE) is found even under a magnetic field change of 0-50 kOe. The high-pressure cubic phase HoAl3, prepared by a rapid-solidification process, is antiferromagnetically ordered below $T^{\rm cub}_{\rm N} =$ 15 K. Magnetic and specific heat measurements reveal that this long-range AFM state becomes unstable as the temperature drops and then it is replaced by a magnetic glassy state below a spin freezing temperature $T_{\rm f} =$ 11 K. The successive changes in magnetic state result in complicated temperature and field dependence of the MCE at low temperatures., Journal of Magnetism and Magnetic Materials Accepted

Layered transition metal chalcogenides (Zr,Hf)GeTe4 were screened from the AtomWork database as potential pressure-induced superconductors by having a narrow bandgap and high density of states near...

Processing magnetocaloric materials into magnetic refrigerant particles is an essential issue in developing high-performance magnetic refrigerators. Here, we succeed in stably producing magnetocaloric particles of the promising material HoAl2 by a newly devised method based on electrode induction melting gas atomization process. The particle size range is on the order of submillimeter, which is suitable for practical refrigeration systems. The resulting particles with less contamination have good morphological, magnetic, and magnetocaloric properties: (i) almost spherical shapes with few internal pores, (ii) a sharp ferromagnetic transition around 30 K, and (iii) a large magnetocaloric effect comparable to the bulk counterpart. These features suggest the HoAl$_{2}$ gas-atomized particles have the potential of use as a magnetic refrigerant. The presented method can be applied not only to HoAl2 but also to other brittle magnetocaloric materials with high melting points, facilitating the production of various magnetic refrigerants needed to develop magnetic refrigerators for hydrogen liquefaction.

Recently, a massive magnetocaloric effect near the liquefaction temperature of hydrogen has been reported in the ferromagnetic material HoB$_{2}$. Here we investigate the effects of Dy substitution in the magnetocaloric properties of Ho$_{1-x}$Dy$_{x}$B$_{2}$ alloys ($\textit{x}$ = 0, 0.3, 0.5, 0.7, 1.0). We find that the Curie temperature ($\textit{T}$$_{C}$) gradually increases upon Dy substitution, while the magnitude of the magnetic entropy change |$\Delta \textit{S}_{M}$| at $\textit{T}$ = $\textit{T}_{C}$ decreases from 0.35 to 0.15 J cm$^{-3}$ K$^{-1}$ for a field change of 5 T. Due to the presence of two magnetic transitions in these alloys, despite the change in the peak magnitude of |$\Delta \textit{S}_{M}$|, the refrigerant capacity ($\textit{RC}$) and refrigerant cooling power ($\textit{RCP}$) remains almost constant in all doping range, which as large as 5.5 J cm$^{-3}$ and 7.0 J cm$^{-3}$ for a field change of 5 T. These results imply that this series of alloys could be an exciting candidate for magnetic refrigeration in the temperature range between 10-50 K., Comment: 19 pages, 5 figures, 2 tables

We fabricate gas-atomized particles by inductively melting electrode rods of HoB2-x (x = -0.3, 0, 0.3, and 1.0) and investigate the effect of non-stoichiometry on the phase fraction, microstructure, and physical properties. Shifting the stoichiometric ratio of the electrode rod to the B (Ho)-rich side increases HoB4 (Ho) phase in the resulting atomized particles. Even if the atomized particles contain 15-20 weight percent (wt.%) of the impurity phase, the influence of which on the physical properties is less severe: the maximum value of the magnetic entropy change is only reduced by 10% compared to HoB2.0 particles. We further find that the ductile Ho phase exists so as to fill the space between the brittle HoB2 phases in the atomized particles, which may be beneficial to the mechanical properties of the particles. Our findings suggest that it would be better to use the Ho-rich electrode rods than the stoichiometric ones to produce HoB2-x particles with more suitable properties as a magnetic refrigerant for magnetic refrigeration systems.

Processing magnetocaloric materials into magnetic refrigerants with appropriate shapes is essential for the development of magnetic refrigeration systems. In this context, the impact of processing on the physical properties of magnetocaloric materials is one of the important issues. Here, we investigate the crystallographic, magnetic, and magnetocaloric properties of gas-atomized particles of the intermetallic compound ErCo$_{2}$, a giant magnetocaloric material for low-temperature applications. The results demonstrate that the physical properties of ErCo$_{2}$ are significantly changed by atomization and subsequent thermal annealing. In the as-atomized particles, the magnetic transition temperature increases from 34 to 56 K and the phase transition changes from first order to second order. The thermal annealing shifts the transition temperature back to the original one and restores the first-order phase transition characteristic. The changes in magnetic properties are closely related to those in crystallographic properties, suggesting the importance of the magneto-structural coupling. The magnetic entropy change $-\Delta S_{M}$ of the particles can be tuned in size, shape, and peak temperature depending on the annealing conditions. The peak value of $-\Delta S_{M}$ varies in the range of 9--33 J kg$^{-1}$ K$^{-1}$ for a magnetic field change of 0--5 T. All the ErCo$_{2}$ atomized particles have magnetocaloric properties comparable or superior to other promising candidates for low-temperature magnetic refrigerants., Comment: Journal of Alloys and Compounds (in press)

For performing successful measurements within limited experimental time, efficient use of preliminary data plays a crucial role. This work shows that a simple feedforward type neural networks approach for learning preliminary experimental data can provide quick access to simulate the experiment within the learned range. The approach is especially beneficial for physical properties measurements with scanning on multiple axes, where derivative or integration of data are required to obtain the objective quantity. Due to its simplicity, the learning process is fast enough for the users to perform learning and simulation on-the-fly by using a combination of open-source optimization techniques and deep-learning libraries. Here such a tool for augmenting the experimental data is proposed, aiming to help researchers to decide the most suitable experimental conditions before performing costly experiments in real. Furthermore, this tool can also be used from the perspective of taking advantage of reutilizing and repurposing previously published data, accelerating data-driven exploration of functional materials., Comment: 19 pages, 5 figures + 7 pages of Supporting Information

The processing of promising magnetocaloric materials into spheres is one of the important issues on developing high-performance magnetic refrigeration systems. In the present study, we achieved in producing spherical particles of a giant magnetocaloric compound HoB2 by a crucible-free gas atomization process, despite its high melting point of 2350 C. The particle size distribution ranges from 100 to 710 micrometers centered at 212-355 micrometers with the highest yield of 14-20wt% of total melted electrode, which is suitable for magnetic refrigeration systems. The majority of the resulting particles are mostly spherical with no contamination during the processing, while unique microstructures are observed on the surface and inside. These spherical particles exhibit sharp magnetic transitions and huge magnetic entropy change of 0.34 J cm^{-3} K^{-1} for a magnetic field change of 5 T at 15.5 K. The high sphericality and the high magnetocaloric performance suggest that the HoB2 gas-atomized particles have good potential as magnetic refrigerants for use in magnetic refrigerators for hydrogen liquefaction., Comment: 6pages(double column), 6 figures

A high-throughput first-principles calculation-assisted data-driven approach based on an inorganic materials database named AtomWork was performed to explore new superconducting materials. Specific band structures of a small band gap and flat band at band edges were used in a screening procedure. Among the candidates studied, we focused on AgIn5Se8, which shows a high density of state at the Fermi level. Single crystals of AgIn5Se8 were successfully obtained via a melt and slow cooling method. The valence states in AgIn5Se8 were estimated to be Ag1+, In3+, and Se2- using X-ray photoelectron spectroscopy. An electrical transport property of resistance was measured under high pressure using an electrodes-inserted diamond anvil cell. The sample exhibited an insulator-to-metal transition with a drastic decrease of the resistance by increasing the pressure up to 24.8 GPa. A possibility of a pressure-driven phase transition below this pressure was indicated by an enthalpy calculation. At a higher pressure region of 52.5 GPa, a pressure-induced superconducting transition was observed at 3.4 K. The maximum transition temperature was increased up to 3.7 K under the pressure of 74.0 GPa.

Data-driven exploration for pressure-induced superconductors was performed based on the high-throughput first-principles screening of electronic band structures. In the screening conditions, we foc...

Analysis of XRD diffraction patterns is one of the keystones of materials science and materials research. With the advancement of data-driven methods for materials design, candidate materials can be quickly screened for the study of a desired physical property. Efficient methods to automatically analyze and identify phases present in a given pattern, are paramount for the success of this new paradigm. To aid this process, the open source python package Xray Estimation and Refinement Using Similarity (XERUS) for semi-automatic/automatic phase identification is presented. XERUS takes advantages of open crystal structure databases, not relying on proprietary databases, to obtain crystal structures on the fly, being then chemical space agnostic. By wrapping around GSASII, it can automatically simulate patterns and calculate similarity measures used for phase identification. Our approach is simple and quick but also applicable to multiphase identification, by coupling the similarity calculations with quick refinements followed by an iterative peak removal process. XERUS is shown in action in four different experimental datasets and also it is benchmarked against a recently proposed deep learning method for a mixture dataset covering the Li-Mn-O-F chemical space. XERUS will be freely available on https://www.github.com/pedrobcst/Xerus/

Recently, ${\mathrm{HoB}}_{2}$ was discovered to undergo a gigantic magnetic entropy change; the largest $|\mathrm{\ensuremath{\Delta}}{S}_{M}|=40.1\phantom{\rule{0.16em}{0ex}}\mathrm{J}\phantom{\rule{0.16em}{0ex}}{\mathrm{kg}}^{\ensuremath{-}1}\phantom{\rule{4pt}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ ($0.35\phantom{\rule{0.16em}{0ex}}\mathrm{J}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}\phantom{\rule{4pt}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$) in magnetocaloric materials studied for hydrogen liquefaction [P. Baptista de Castro et al., NPG Asia Mater. 12, 35 (2020)]. In this study, in order to investigate the origin of the gigantic $|\mathrm{\ensuremath{\Delta}}{S}_{M}|$ in ${\mathrm{HoB}}_{2}$, we studied the magnetic orderings by neutron diffraction with an enriched powder sample of ${\mathrm{Ho}}^{11}{\mathrm{B}}_{2}$. Our experimental results showed the onset of ferromagnetic long-range order below ${T}_{C}=15\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. For the second phase transition at ${T}_{2}=11\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, the spin reorientation occurs, and the temperature dependence of the total magnetic moment of ${\mathrm{Ho}}^{3+}$ shows a kink anomaly, which is typically seen in compounds with quadrupolar ordering. In addition, the temperature dependence of the ferromagnetic short-range order above ${T}_{C}$ is strongly related to that of the magnetic entropy change in ${\mathrm{HoB}}_{2}$. These results infer that the gigantic $|\mathrm{\ensuremath{\Delta}}{S}_{M}|$ in ${\mathrm{HoB}}_{2}$ is caused by (i) the spin reorientation transition, which is likely associated with quadrupolar ordering, giving the additional contribution to $|\mathrm{\ensuremath{\Delta}}{S}_{M}|$ at the lower phase transition temperature, ${T}_{2}=11\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, and (ii) the large FM fluctuation above ${T}_{C}$ with origins in the strong suppression of the FM long-range order.

Sphingomyelin synthase 1 (SMS1) contributes to the generation of membrane sphingomyelin (SM) and affects SM-mediated physiological functions. Here, we describe the hematologic phenotypes, such as reduced circulating platelets and dysfunctional hemostasis, in SMS1-deficient (SMS1-KO) mice. SMS1-KO mice display pathologic manifestations related to idiopathic thrombocytopenia (ITP), including relatively high amounts of peripheral blood reticulated platelets, enhanced megakaryopoiesis in the bone marrow and spleen, and splenomegaly. Deficiency of SMS1, but not SMS2, prevented SM production and enhanced phosphatidylserine (PS) externalization on the plasma membranes of platelets and megakaryocytes. Consequently, SMS1-KO platelets were excessively cleared by macrophages in the spleen. Multimer formation in the plasma membrane of TMEM16F, a known calcium (Ca2+)-activated nonselective ion channel and Ca2+-dependent PS scramblase, was enhanced; the result was PS externalization to outer leaflets through increased Ca2+ influx in immortalized mouse embryonic fibroblasts established from SMS1-KO mice (SMS1-KO tMEFs), as seen with SMS1-KO platelets. Thus, SMS1 deficiency changed the TMEM16F distribution on the membrane microdomain, regulating Ca2+ influx-dependent PS exposure. SMS1-KO tMEFs in which TMEM16F was knocked out by using the CRISPR/Cas9 system lacked both the Ca2+ influx and excess PS exposure seen in SMS1-KO tMEFs. Therefore, SM depletion on platelet membrane microdomains due to SMS1 deficiency enhanced PS externalization via a Ca2+ influx through TMEM16F activation, leading to elevated platelet clearance and causing hemostasis dysfunction through thrombocytopenia. Our current findings show that the SM-rich microdomain generated by SMS1 is a potent regulator of thrombocytopenia through TMEM16F, suggesting that its dysfunction may be a novel additional mechanism of ITP.

Magnetic refrigeration exploits the magnetocaloric effect which is the entropy change upon application and removal of magnetic fields in materials, providing an alternate path for refrigeration other than the conventional gas cycles. While intensive research has uncovered a vast number of magnetic materials which exhibits large magnetocaloric effect, these properties for a large number of compounds still remain unknown. To explore new functional materials in this unknown space, machine learning is used as a guide for selecting materials which could exhibit large magnetocaloric effect. By this approach, HoB$_{2}$ is singled out, synthesized and its magnetocaloric properties are evaluated, leading to the experimental discovery of gigantic magnetic entropy change 40.1 J kg$^{-1}$ K$^{-1}$ (0.35 J cm$^{-3}$ K$^{-1}$) for a field change of 5 T in the vicinity of a ferromagnetic second-order phase transition with a Curie temperature of 15 K. This is the highest value reported so far, to our knowledge, near the hydrogen liquefaction temperature thus it is a highly suitable material for hydrogen liquefaction and low temperature magnetic cooling applications., 12 pages including 3 figures and 1 table + 11 pages of supplementary information. Published version available at: https://rdcu.be/b36ep

We have developed an approach to control the carrier density in various material under high pressure by the combination of an electric double layer transistor (EDLT) with a diamond anvil cell (DAC). In this study, this EDLT-DAC was applied to a Bi thin film, and here we report the field-effect under high pressure in the material. Our EDLT-DAC is a promising device for exploring unknown physical phenomena such as high transition-temperature superconductivity (HTS)., 10 pages, 4 figures

Here we firstly report the pressure-induced superconductivity in phase change materials SnSb

Physical review / B 101(2), 020508 (2020). doi:10.1103/PhysRevB.101.020508, The coexistence of phases, characterized by different electronic degrees of freedom, commonly occurs in layered superconductors. Among them, alkaline intercalated chalcogenides are model systems showing the microscale coexistence of paramagnetic (PAR) and antiferromagnetic (AFM) phases, however, the temporal behavior of different phases is still unknown. Here, we report a visualization of the atomic motion in the granular phase of KxFe2−ySe2 using x-ray photon correlation spectroscopy. Unlike the PAR phase, the AFM texture reveals an intermittent dynamics with avalanches as in martensites. When cooled down across the superconducting transition temperature Tc, the AFM phase goes through an anomalous slowing behavior, suggesting a direct relationship between the atomic motions in the AFM phase and the superconductivity. In addition to providing compelling evidence of avalanchelike dynamics in a layered superconductor, the results provide a basis for different theoretical models to describe the quantum states in inhomogeneous solids., Published by Inst., Woodbury, NY

We report the fabrication of ErAl2 magnetocaloric wires by a powder-in-tube method (PIT) and the evaluation of magnetic entropy change through magnetization measurements. The magnetic entropy change of ErAl2 PIT wires exhibits similar behavior to the bulk counterpart, while its magnitude is reduced by the decrease in the volume fraction of ErAl2 due to the surrounding non-magnetic sheaths. We find that another effect reduces the magnetic entropy change of the ErAl2 PIT wires around the Curie temperature, and discuss its possible origin in terms of a correlation between magnetic properties of ErAl2 and mechanical properties of sheath material., Comment: This is the version of the article before peer review or editing, as submitted by an author to {insert name of Journal}. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at {https://dx.doi.org/10.1088/1361-6463/ab5c71}

A magnetic refrigerator that makes use of the magneto-caloric effect realizes a highly efficient cooling device. Since the cooling power of magnetic refrigerators depends largely on the strength of the magnetic field, the use of a superconducting magnet is essential. Using magnetic refrigeration, achieving a liquefaction efficiency of larger than 50% is theoretically possible, which is twice that of conventional gas expansion refrigerators. In this study, an active magnetic regenerative refrigerator, one of the magnetic refrigerators using a superconducting solenoid, was built and hydrogen liquefaction was successfully demonstrated.

Candidate compounds for new thermoelectric and superconducting materials, which have narrow band gap and flat bands near band edges, were exhaustively searched by the high-throughput first-principles calculation from an inorganic materials database named AtomWork. We focused on PbBi2Te4 which has the similar electronic band structure and the same crystal structure with those of a pressure-induced superconductor SnBi2Se4 explored by the same data-driven approach. The PbBi2Te4 was successfully synthesized as single crystals using a melt and slow cooling method. The core level X-ray photoelectron spectroscopy analysis revealed Pb2+, Bi3+ and Te2- valence states in PbBi2Te4. The thermoelectric properties of the PbBi2Te4 sample were measured at ambient pressure and the electrical resistance was also evaluated under high pressure using a diamond anvil cell with boron-doped diamond electrodes. The resistance decreased with increasing of the pressure, and pressure-induced superconducting transitions were discovered at 2.5 K under 10 GPa. The maximum superconducting transition temperature increased up to 8.4 K at 21.7 GPa. The data-driven approach shows promising power to accelerate the discovery of new thermoelectric and superconducting materials.

The crystal structure of type I clathrate Ba8Al16Ge30 prepared by arc melting in argon atmosphere has been studied by using a neutron powder diffractometer from 10 to 900 K. We found that the site preferences in the host structure were relevant to the guest atom features, which agrees with a previous report. Data were analyzed using two models for the Ba atom position in the larger cage (Ba2): an on-center 6d-site model and an off-center 24k-site one. The Maximum Entropy Method (MEM) results agree well with the 24k model and the shape of the nuclear density distribution of Ba2 atom evolves with increasing temperature.

It is now well established that the microstructure of Fe-based chalcogenide K x Fe2−ySe2 consists of, at least, a minor (~15 percent), nano-sized, superconducting K s Fe2Se2 phase and a major (~85 percent) insulating antiferromagnetic K2Fe4Se5 matrix. Other intercalated A1−xFe2−ySe2 (A = Li, Na, Ba, Sr, Ca, Yb, Eu, ammonia, amide, pyridine, ethylenediamine etc.) manifest a similar microstructure. On subjecting each of these systems to a varying control parameter (e.g. heat treatment, concentration x,y, or pressure p), one obtains an exotic normal-state and superconducting phase diagram. With the objective of rationalizing the properties of such a diagram, we envisage a system consisting of nanosized superconducting granules which are embedded within an insulating continuum. Then, based on the standard granular superconductor model, an induced variation in size, distribution, separation and Fe-content of the superconducting granules can be expressed in terms of model parameters (e.g. tunneling conductance, g, Coulomb charging energy, E c , superconducting gap of single granule, Δ, and Josephson energy J = πΔg/2). We show, with illustration from experiments, that this granular scenario explains satisfactorily the evolution of normal-state and superconducting properties (best visualized on a $${\boldsymbol{g}}{\boldsymbol{-}}\frac{{{\boldsymbol{E}}}_{{\boldsymbol{c}}}}{{\boldsymbol{\Delta }}}{\boldsymbol{-}}{\boldsymbol{T}}$$ g − E c Δ − T phase diagram) of A x Fe2−ySe2 when any of x, y, p, or heat treatment is varied.

DyNi $$_{2}$$ B $$_{2}$$ C superconducts at $$T_{c} \approx 6\,{\text{K}}$$ and orders antiferromagnetically at $$T_{N}\approx 10\,{\text{K}}.$$ Its non-superconducting isomorph DyCo $$_{2}$$ B $$_{2}$$ C is a ferromagnet with $$T_{C}\approx 6\,{\text{K}}.$$ With the aim of mapping out the magnetic properties, in particular magnetic structures, of their solid solutions, we synthesized $$^{11}$$ B-enriched Dy(Co $$_{x}$$ Ni $$_{1-x}$$ ) $$_{2}$$ B $$_{2}$$ C ( $$x=0.2,0.4,0.6,0.8$$ ). We investigated the evolution of their magnetic, thermal and transport properties by means of the magnetization, resistivity, specific heat and neutron diffraction techniques. Their crystal structures were confirmed to be ThCr $$_{2}$$ -Si $$_{2}$$ -type tetragonal (I4/mmm) phase. The magnetic structure was found to be antiferromagnetic with k0.2 = (0, 0, 1) for x = 0.2; helicoidal with k $$_{0.4}$$ = (0, 0, 0.49) and k $$_{0.6}$$ = (0, 0, 0.46) for, respectively, x = 0.4 and 0.6 and ferromagnetic with k $$_{0.8}$$ = (0, 0, 0) for x = 0.8. We discuss the evolution of such magnetic modes assuming a scenario of an idealized one-dimensional chain of transverse magnetic moments.

Layered ternary transition-metal chalcogenides have been focused as a vein of exploration for superconductors. In this study, TiGeTe6 single crystals were synthesized and characterized by structural and valence state analyses and electrical transport measurements. The transport properties were measured under various pressures up to 71 GPa. The activation energy gets smaller as the applied pressure increases, and a signature of a pressure-induced metallization was observed under around 8.4 GPa. Under 13 GPa, pressure-induced superconductivity was discovered in this compound for the first time, with successive drops at 3 K and 6 K in the resistance, indicating the presence of multiple superconducting transitions. The superconducting transition temperature kept increasing as we further applied the pressure to the TiGeTe6 single crystal in the performed pressure range, reaching as high as 8.1 K under 71 GPa.

A method to directly deposit boron-doped amorphous carbon films via focused ion beam-assisted chemical vapor deposition is reported. The presence of boron in the deposited films was verified by X-ray photoelectron spectroscopy. Raman spectroscopy analysis confirmed the amorphousity of the films. The as-deposited films exhibited typical semiconducting behavior from electrical resistance versus temperature measurements. The presented fabrication technique is a one step process for the simultaneous deposition, boron-doping, and patterning of the films, and hence may offer an effective way to directly fabricate boron-doped amorphous carbon-based devices without the need for templates, which is highly advantageous for applications.

For many years, cerium-aluminum systems have been extensively studied because of their unusual magnetic behavior. As the atomic radii of cerium and aluminum differ greatly from each other, a solid solution is not obtained because of the Hume-Rothery rule. Therefore, intermetallic compounds are usually studied, and structural stability is crucial for further discussion of their physical properties. The present article reports on high-energy ball milling of the intermetallic compound Ce3Al at room temperature. It has been found that non-equilibrium supersaturated Ce solid solution was formed during the milling. The solubility of aluminum was estimated as 5 to 13 at. pct from the peak shifts of the X-ray diffraction pattern. The structural changes in the initial stages of the milling were also studied.

Microscopic coexistence between weak ferromagnetism (WFM) and superconductivity (SC) in T b 0.47 Y 0.53 N i 2 11 B 2 C was investigated. Magnetization measurements indicate that antiferromagnetic (AFM), WFM and SC transitions occur in this material. Unpolarized neutron diffraction experiments revealed that the AFM order is best described by a longitudinal spin density wave with a propagation vector of q = 0.550 a ∗ . Polarized neutron diffraction experiments further confirmed that the WFM order is originated in T b 0.47 Y 0.53 N i 2 11 B 2 C .

A high-throughput first-principles calculation-assisted data-driven approach based on an inorganic materials database named AtomWork was performed to explore new superconducting materials. Specific band structures of a small band gap and flat band at band edges were used in a screening procedure. Among the candidates studied, we focused on AgIn

We study the effects of the Al substitution by Ga on the crystal structures of type I clathrate Ba 8 Al 16-x Ga x Ge 30 (x = 2, 4, 6, and 8) by neutron powder diffraction. The diffraction data were refined using two models for Ba guest atom position in the oversized cage (Ba2): on center (6d site) and off-center (24k site) model. We also carried out the Maximum Entropy Method (MEM) analysis. The 24k model is in a good agreement with the Maximum Entropy Method (MEM) results. The evolution of nuclear density distribution with increasing temperature of Ba 8 Al 8 Ga 8 Ge 30 was revealed by MEM analysis.

Polycrystalline samples of layered pnictogen (Pn) diselenide $\mathrm{Nd}{\mathrm{O}}_{0.8}{\mathrm{F}}_{0.2}\mathrm{S}{{\mathrm{b}}_{1}}_{\ensuremath{-}x}\mathrm{B}{\mathrm{i}}_{x}\mathrm{S}{\mathrm{e}}_{2}(x=0\phantom{\rule{0.16em}{0ex}}\mathrm{to}\phantom{\rule{0.16em}{0ex}}0.8)$ were successfully synthesized by solid-state reactions. Electrical resistivity in the synthesized samples systematically decreases with an increase in Bi content $x$, accompanied by an insulator to metal-like transition at $x=0.5\ensuremath{-}0.6$. Crystal structure analysis using synchrotron x-ray diffraction suggests that this transition correlates with anomalous change in $c$-axis length and/or distortion in Pn\ensuremath{-}Se conducting plane. Emergence of pressure-induced superconductivity was investigated using a diamond anvil cell with boron-doped diamond electrodes, employing $x=0.3$ and 0.7 as the representative samples. For the Sb-rich one $(x=0.3)$, we observed a signature of superconducting transition with ${{T}_{c}}^{\mathrm{onset}}=5.15\ifmmode\pm\else\textpm\fi{}0.05\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ at 50 GPa. The ${{T}_{c}}^{\mathrm{onset}}$ of $x=0.3$ increased with increasing pressure and reached 7.65 \ifmmode\pm\else\textpm\fi{} 0.05 K at 70.8 GPa, followed by the gradual decrease in ${T}_{c}$ up to 90 GPa. For the Bi-rich one $(x=0.7)$, a superconducting transition with ${{T}_{c}}^{\mathrm{onset}}=5.5\ifmmode\pm\else\textpm\fi{}0.6\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ was induced at 43.5 GPa, which is almost comparable to that of $x=0.3$; besides, upper critical field $({H}_{c2})$ is evaluated to be $\ensuremath{\sim}10$ T for $x=0.7$, which is higher than that of $x=0.3\phantom{\rule{4pt}{0ex}}({H}_{c2}=6.7$ T at 50 GPa).

A direct patterning technique of gallium-irradiated superconducting silicon has been established by a focused gallium-ion beam without any mask-based lithography process. The electrical transport measurements for line- and square-shaped patterns of gallium-irradiated silicon were carried out under self-field and magnetic field up to 7 T. Sharp superconducting transitions were observed in both patterns at a temperature of 7 K. The line pattern exhibited a signature of higher onset temperature at around 12 K. A critical dose amount to obtain the superconducting gallium-irradiated silicon was investigated by the fabrication of various samples with different doses. This technique can be used as a simple fabrication method for a superconducting device.

Tin sulfide (SnS) single crystals were synthesized using a melt and slow-cooling method. The obtained crystals were characterized by x-ray diffraction, energy-dispersive spectrometry, and by x-ray photoelectron spectroscopy. Electrical transport properties of SnS were investigated under high pressure using a diamond anvil cell with boron-doped metallic diamond electrodes and an undoped diamond insulating layer. We successfully observed an insulator to metal transition between 8.1 and 12.5 GPa and pressure-induced superconductivity with a transition temperature (${T}_{c}$) of 5.8 K under 47.8 GPa as predicted by theoretical calculations. Comparing with the pressure-induced superconductivity in related SnSe compound, a possible ${T}_{c}$ enhancement in SnS by an increase of density of states at the Fermi level is expected.

We have successfully synthesized the c-axis oriented YBa2Cu4O8 (Y-124) film on a SrTiO3 (1 0 0) substrate via a coprecipitation and a dip-coating method. The precipitations including Y, Ba and Cu ions were obtained using their metal nitrates solution and the aqueous solution of sodium hydroxide and oxalic acid. Superconducting transition of the synthesized film was observed at 64-70 K corresponding to bulk Y-124 in the magnetization and resistance measurement. The developed method is suitable to synthesize superconducting Y-124 films for technological applications., Comment: 7 pages, 6 figures

To optimize the giant magnetocaloric properties of HoB2, we synthesized and characterized the magnetocaloric properties of Ho1-xGdxB2 (0.1 ≤ x ≤ 0.4) alloys. We found out that Gd enters stoichiometrically and randomly into the Ho site, leading to a Vegard-type structural change. The addition of spherical S7/2 Gd3+ moments prompts an enhancement in Curie temperature from 15 K to 30 K (at x = 0.4), a reduction in peak value of the magnetic entropy change, from 0.35 (40.1) to 0.17 (20.2) J cm−3 K−1 (J kg−1 K−1), and a broadening of the magnetic entropy change curves. The overall influence is a relatively high refrigerant capacity and relative cooling power, peaking at 6.07 (711) and 7.68 (899) J cm−3 (J kg−1) for x = 0.2, and an extension of the thermal working range to higher temperatures. Unlike Ho1−xDyxB2 alloys, the Gd substituted samples show no magnetic hysteresis. Furthermore, scaling analysis of the entropy curves suggests a second-order phase transition for the ferromagnetic transition in these alloys. Thus, Ho1-xGdxB2 alloys are potential candidates for cryogenic refrigeration applications.

Cuprate superconductor Bi2Sr2CaCu2O8+δ (BSCCO) has been a promising candidate of a coherent, continuous, and compact THz light source owing to its intrinsic Josephson junction (IJJ) inside the crystal structure. In this paper, we utilized BSCCO cross-whisker (CW) junctions to produce THz emitter device using the whisker crystals which can be easily obtained compared with single crystals. As a result, we have successfully observed the emission from the CW IJJ at the frequency of ∼0.7 THz, which is the first observation of a THz emission from whiskers to our knowledge. Our findings would enlarge the applicability of BSCCO superconductors for compact THz emission sources.