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Cross polarization (CP) is a widely used solid-state nuclear magnetic resonance (NMR) technique for enhancing the polarization of dilute S spins from much larger polarization of abundant I spins such as 1H. To achieve such a polarization transfer, the I spin should either be spin-locked or be converted to the dipolar ordered state through adiabatic demagnetization in the rotating frame. In this work, we analyze the spin dynamics of the Hartmann-Hahn CP (HHCP) utilizing the 1H spin-locking, and the dipolar-order CP (DOCP) having the 1H adiabatic demagnetization. We further propose an adiabatic demagnetization CP (ADCP) where a constant radio-frequency pulse is applied on the S spin while 1H is adiabatically demagnetized. Our analyses indicate that ADCP utilizes the adiabatic passage to effectively achieve the polarization transfer from the 1H to S spins. In addition, the dipolar ordered state generated during the 1H demagnetization process could also be converted into the observable S polarization through DOCP, further enhancing the polarized signals. It is shown by both static and magic-angle-spinning (MAS) NMR experiments that ADCP has dramatically broadened the CP matching condition over the other CP schemes. Various samples have been used to demonstrate the polarization transfer efficiency of this newly proposed ADCP scheme.

We have investigated the magnetic and magnetocaloric properties of antiferromagnetic Ising spin chain CoV2O6 by magnetization and heat capacity measurements. Both monoclinic α-CoV2O6 and triclinic γ-CoV2O6 exhibit field-induced metamagnetic transitions from antiferromagnetic to ferromagnetic state via an intermediate ferrimagnetic state with 1/3 magnetization plateau. Due to the field-induced metamagnetic transitions, these systems show large conventional as well as inverse magnetocaloric effects. In α-CoV2O6, we observe field-induced complex magnetic phases and multiple magnetization plateaus below 6K when the field is applied along c axis. Several critical temperatures and fields have been identified from the temperature and field dependence of magnetization, magnetic entropy change, and heat capacity to construct the H-T phase diagram. As compared to α-CoV2O6, γ-CoV2O6 displays a relatively simple magnetic phase diagram. Due to the large magnetic entropy change and adiabatic temperature change at low or moderate applied magnetic field, γ-CoV2O6 may be considered as a magnetic refrigerant in the low-temperature region below 20 K. [ABSTRACT FROM AUTHOR]

The influence of Fe doping for Mn in CoMn1-xFexGe alloys on their structural and magnetic phase transitions was investigated. CoMn1-xFexGe alloys display a first-order magneto-structural transition from a high temperature paramagnetic hexagonal Ni2In-type crystal structure to a low temperature ferromagnetic orthorhombic TiNiSi-type structure. An entropy change of ΔSM=-32.8 J/kgK was measured and adiabatic temperature change of -8.0K was computed for the x=0.085 alloy under a magnetic field of 7 T in the vicinity of the phase transition at 317 K. With increasing Fe content, transition temperatures and magnetic entropy changes decrease. In addition to investigating the effect of replacing Mn with Fe, the accessibility of the giant measured entropy change was quantified by means of the minimum magnetic field required to start and to complete the magnetostructural phase transition. [ABSTRACT FROM AUTHOR]

We have investigated the magnetic and magnetocaloric properties of antiferromagnetic Ising spin chain CoV2O6 by magnetization and heat capacity measurements. Both monoclinic α-CoV2O6 and triclinic γ-CoV2O6 exhibit field-induced metamagnetic transitions from antiferromagnetic to ferromagnetic state via an intermediate ferrimagnetic state with 1/3 magnetization plateau. Due to the field-induced metamagnetic transitions, these systems show large conventional as well as inverse magnetocaloric effects. In α-CoV2O6, we observe field-induced complex magnetic phases and multiple magnetization plateaus below 6K when the field is applied along c axis. Several critical temperatures and fields have been identified from the temperature and field dependence of magnetization, magnetic entropy change, and heat capacity to construct the H-T phase diagram. As compared to α-CoV2O6, γ-CoV2O6 displays a relatively simple magnetic phase diagram. Due to the large magnetic entropy change and adiabatic temperature change at low or moderate applied magnetic field, γ-CoV2O6 may be considered as a magnetic refrigerant in the low-temperature region below 20 K. [ABSTRACT FROM AUTHOR]

Structural and magnetic properties of Fe/Pt core-shell nanostructure prepared by a sequential reduction process are reported. Transmission electron microscopy shows nearly spherical particles fitting a lognormal size distribution with Do=3.0 nm and distribution width λD=0.31. In x-ray diffraction, Bragg lines only from the Pt shell are clearly identified with line-widths yielding crystallite size=3.1 nm. Measurements of magnetization M vs. T (2K-350K) in magnetic fields up to 90 kOe show a blocking temperature TB=13K below which hysteresis loops are observed with coercivity HC increasing with decreasing T reaching HC=750Oe at 2 K. Temperature dependence of the ac susceptibilities at frequencies fm=10 Hz-5 kHz is measured to determine the change in TB with fm using the Vogel-Fulcher law. This analysis shows the presence of significant interparticle interaction, the Neel-Brown relaxation frequency fo=5.3×1010Hz and anisotropy constant Ka=3.6×106 ergs/ cm3. A fit of the M vs. H data up to H=90 kOe for T>TB to the modified Langevin function taking particle size distribution into account yields magnetic moment per particle consistent with the proposed core-shell structure; Fe core of 2.2 nm diameter and Pt shell of 0.4 nm thickness. [ABSTRACT FROM AUTHOR]

• A two-stage adiabatic demagnetization refrigerator is built with GGG as the first stage and CPA as the second stage. • A 3D printed PEEK suspension system is used at the second stage. • A no-load lowest temperature of 66.1 mK is achieved at the second stage when starting from 1 K@4 T. • Simulations estimate each PEEK suspension has a 1.10 μW thermal leak between 4 K and 0.3 K and a further reduction with a 1 K heat sink in the middle. • Experiments validate the effectiveness of 1 K heat sink. The salt pill suspensions play a critical role in determining the performance of adiabatic demagnetization refrigerators (ADR). Kevlar suspensions are commonly used to hold the salt pill in place and to minimize the thermal leak. However, traditional solutions such as tensioning the Kevlar and fixing it on mechanical frame with the help of epoxy or running it around a pulley are quite challenging. This paper presents an innovative suspension using 3D printing technology and a polyether ether ketone (PEEK) multi-ring suspension has been designed and tested. Numerical analysis shows that a single piece of the suspension may contribute about 1.10 μW thermal leak between 4 K and 0.3 K. To test its performance, a two-stage ADR is built with Gadolinium Gallium Garnet (GGG) as the first stage and chromium potassium alum (CPA) salt pill as the second stage which is supported by the PEEK suspension. The GGG stage is mainly used to provide an initial temperature for CPA stage. Typically, starting from 1 K@4 T, a no-load lowest temperature of 66.1 mK is achieved at a demagnetization rate of 0.005 T/s in the experiments. The thermal leak of the PEEK suspension with and without 1 K heat sink has been analyzed and compared, with the former one showing a big reduction of the thermal leak. This paper confirms the feasibility of PEEK as an ADR suspension material and provides a potential 3D printing method for complex suspension designs. [ABSTRACT FROM AUTHOR]

Magnetic and magnetocaloric properties of a spin-1 Heisenberg diamond cluster with two different coupling constants are investigated with the help of an exact diagonalization based on the Kambe's method, which employs a local conservation of composite spins formed by spin-1 entities located in opposite corners of a diamond spin cluster. It is shown that the spin-1 Heisenberg diamond cluster exhibits several intriguing quantum ground states, which are manifested in low-temperature magnetization curves as intermediate plateaus at 1/4, 1/2, and 3/4 of the saturation magnetization. In addition, the spin-1 Heisenberg diamond cluster may also exhibit an enhanced magnetocaloric effect, which may be relevant for a low-temperature refrigeration achieved through the adiabatic demagnetization. It is evidenced that the spin-1 Heisenberg diamond cluster with the antiferromagnetic coupling constants J¹/kB = 41.4 K and J2/kB = 9.2 K satisfactorily reproduces a low-temperature magnetization curve recorded for the tetranuclear nickel complex [Ni4(μ-CO3)2(aetpy)8](ClO4)4 (aetpy = 2-aminoethyl-pyridine) including a size and position of intermediate plateaus detected at 1/2 and 3/4 of the saturation magnetization. A microscopic nature of fractional magnetization plateaus observed experimentally is clarified and interpreted in terms of valence-bond crystal with either a single or double valence bond. It is suggested that this frustrated magnetic molecule can provide a prospective cryogenic coolant with the maximal isothermal entropy change -ΔSM=10.6 J·K-1·kg-1 in a temperature range below 2.3 K. [ABSTRACT FROM AUTHOR]

• A low-cost copper-foam based salt pill is designed and manufactured. • A test from 4.3 K @ 4 T with a demagnetization rate of 0.0025 T/s leads to a no-load temperature of 176.5 mK. • Eddy current loss may be an issue with a high demagnetization rate. • Selection of the copper form parameters needs more investigation. Hydrated paramagnetic salt pills are important components in an adiabatic demagnetization refrigerator (ADR) for temperatures below 500 mK. To improve the heat transfer performance between salt crystals and external thermal links, thermal buses are commonly employed inside the salt pill. Common forms of thermal buses are either thin copper pillars made from electric discharge machining (EDM) or wire bundles, both of which generally involve considerable machining or labor. This paper introduces a novel design and fabrication of a simple foam copper-based paramagnetic salt pill. The foam copper has 30 pores per inch (PPI), a porosity of 98 %, 0.005 m2/g specific surface area, and an estimated pore diameter of 0.82 mm. The complete design, assembling process, and growth of the foam copper-based chromium potassium alum (CPA) salt pill (40 mm in length and 23 mm in diameter) are introduced. A single-stage ADR is built based on this salt pill to test its performance, while another salt pill with the wire thermal bus has also been tested for comparison. A typical cool-down from 4.3 K @ 4 T with a demagnetization rate of 0.0025 T/s led to a no-load temperature of 176.5 mK, slightly better than that using a wire thermal bus. In terms of cooling power per gram of salt, the cooling capacities at 600 mK of both salt pills have also been measured and both have shown similar performance. This preliminary study has shown the potential of the foam copper-based salt pill though more research is required to optimize its performance. [ABSTRACT FROM AUTHOR]

Magnetic and magnetocaloric properties of polycrystalline ErSn0.5Ge1.5 have been studied. It is found that substitution of Ge for Sn in ErSn1.1Ge0.9 results in a nominal increase in the magnetic moment, but a considerable enhancement in the magnetocaloric effect. The magnetocaloric effect, calculated from magnetization data, shows a large value of 13 J/kg K for a field of 50 kOe. Magnetization, heat capacity, and magnetocaloric data reveal field induced metamagnetic transition in this compound. [ABSTRACT FROM AUTHOR]

Magnetic and magnetocaloric properties of polycrystalline ErSn0.5Ge1.5 have been studied. It is found that substitution of Ge for Sn in ErSn1.1Ge0.9 results in a nominal increase in the magnetic moment, but a considerable enhancement in the magnetocaloric effect. The magnetocaloric effect, calculated from magnetization data, shows a large value of 13 J/kg K for a field of 50 kOe. Magnetization, heat capacity, and magnetocaloric data reveal field induced metamagnetic transition in this compound. [ABSTRACT FROM AUTHOR]

Dilution and adiabatic demagnetization refrigerators based on pulse tube cryocoolers are nowadays used in many low temperature physics experiments, such as atomic force and scanning tunneling microscopy, quantum computing, radiation detectors, and many others. A pulse tube refrigerator greatly simplifies the laboratory activities being a cryogen-free system. The major disadvantage of a pulse tube cooler is the high level of mechanical vibrations at the warm and cold interfaces that could substantially affect the performance of very sensitive cryogenic instruments. In this paper, we describe the performance of a very simple mechanical attenuation system used to eliminate the pulse-tube-induced low frequency noise of the superconducting transition-edge sensors under development for the instruments of the next generation of infra-red and X-ray space observatories. [ABSTRACT FROM AUTHOR]

In this paper, we study behavior of the correlations, both quantum and classical, under adiabatic demagnetization process in systems of nuclear spins with dipole–dipole interactions in an external magnetic field and in the temperature range including positive and negative temperatures. For a two-spin system, analytical expressions for the quantum and classical correlations are obtained. It is revealed that the field dependences of the quantum and classical correlations at positive and negative temperatures are substantially different. This difference most clearly appears in the case of zero magnetic field: at negative temperature, the measures of quantum correlations tend to the maximum values with a temperature increase. At positive temperature, these quantities tend to zero at a decrease of magnetic field. It is also found that, for the nearest-neighboring spins in the same field, the values of concurrence and discord are larger at negative temperatures than at positive ones. [ABSTRACT FROM AUTHOR]

Highlights • The mechanism of multi-bypass was numerical studied. • Multi-bypass has the functions of orifice and double-inlet, making it like two-stage cryocooler. • A minimum no-load temperature 3.7 K was obtained, and the cooling power was 14 mW@4.2 K. • New mK cooling chain for HUBS satellite was proposed and analyzed. Abstract The Vuilleumier (VM) type pulse tube cryocooler (VPTC) is a new kind of 4 K cryocooler which had been experimentally verified. This paper presents the recent advances on a 4 K VPTC in our laboratory. First, the mechanism of multi-bypass was numerically studied using Sage software. The results showed that the function of the multi-bypass is not only similar to a double-inlet, but also to an orifice, which makes the VPTC work like a two-stage cryocooler. Based on the simulation results, the performance of VPTC was experimentally studied. Under its optimal operating conditions, a no-load temperature of 3.7 K has been obtained, which is the first demonstration of a single-stage VPTC obtaining temperatures below 4 K. It can supply about 14mW cooling power at 4.2 K and about 100 mW cooling power at 35 K simultaneously, which has potential application as the pre-cooler for an adiabatic demagnetization refrigerator (ADR). Finally, based on this VPTC, a new mK cooling chain for HUBS (Hot Universe Baryon Surveyor) satellite is proposed and its prospect has also been theoretically analyzed. [ABSTRACT FROM AUTHOR]

Highlights • Magnetic and magnetocaloric properties of Gd 0.7 Sr 0.3 Mn 1−x Ti x O 3 (x = 0, 0.1 and 0.15). • Isothermal magnetic entropy change (|ΔS(T)|) shows appreciably high values for three compounds. • For 10 T field, maximum magnetic entropy change is 22.2 JKg−1 K−1 for Gd 0.7 Sr 0.3 Mn 0.85 Ti 0.15 O 3. • Magnetic phase transition is second order for all compounds. • −ΔS(T) shows a universal behaviour near the transition region at the low temperature. Abstract This work focuses on Magnetic and magnetocaloric properties of doped Gd based manganites; Gd 0.7 Sr 0.3 Mn 1−x Ti x O 3 (x = 0, 0.1, 0.15) denoted by G, G 0.1 , G 0.15 respectively. Isothermal magnetic entropy change (|ΔS(T)|) shows appreciably high values for the three compounds. For 10 T field, the peak values obtained for magnetic entropy change is 10.4 JKg−1 K−1, 9.6 JKg−1 K−1 and 22.2 JKg−1 K−1respectively for samples G, G 0.1 , G 0.15 at 12.5 K. Interestingly, −ΔS(T) shows a universal behaviour near the transition region at the low temperature. Relative cooling power (RCP) is comparatively high for Gd 0.7 Sr 0.3 Mn 0.85 Ti 0.15 O 3 at low fields, but for high fields Gd 0.7 Sr 0.3 MnO 3 has comparatively high values for RCP. [ABSTRACT FROM AUTHOR]

Abstract Plate impact experiments and dynamic reloading compression tests at 3 × 103 and 4 × 103 s−1 were conducted on the Ti–6Al–4V alloy with bimodal microstructure to investigate the effect of shock prestrain on the dynamic mechanical properties and adiabatic shearing behavior of this alloy. The shock prestrained alloy has higher flow stress but lower uniform plastic strain and impact absorption energy at both reloading strain rates due to the multiplication of dislocations during shock pulse. The Bauschinger effect and the lack of more effective strengthening factors limit the shock-induced strengthening effect in Ti–6Al–4V at an equivalent strain level during reloading at a strain rate of 3 × 103 s−1. However, the shock-induced strengthening effect is somewhat improved at a higher reloading strain rate. Shock prestrain facilitates the formation, bifurcation and interaction of adiabatic shear bands (ASBs) in Ti–6Al–4V through the promotion of the dynamic recovery process at the primary stage of the formation of ASBs. Plugs and clusters of ASBs can form in the shock prestrained Ti–6Al–4V with bimodal microstructure at a relatively low strain rate due to the high density and frequent interactions of ASBs. Highlights • The postshock Ti-64 is hardly reinforced at equivalent strain during dynamic reload. • Adiabatic shear sensitivity enhances in the shock prestrained Ti-64. • Some plugs and clusters of adiabatic shear bands form in the postshock Ti-64. [ABSTRACT FROM AUTHOR]

The low-temperature liquid nitriding of stainless steels can result in the formation of a surface zone of so-called expanded austenite (S-phase) by the dissolution of large amounts of nitrogen in the solid solution and formation of a precipitate-free layer supersaturated with high hardness. Erosion–corrosion measurements were performed on low-temperature nitrided and non-nitrided 316L stainless steels. The total erosion–corrosion, erosion-only, and corrosion-only wastages were measured directly. As expected, it was shown that low-temperature nitriding dramatically reduces the degree of erosion–corrosion in stainless steels, caused by the impingement of particles in a corrosive medium. The nitrided 316L stainless steels exhibited an improvement of almost 84% in the erosion–corrosion resistance compared to their non-nitrided counterparts. The erosion-only rates and synergistic levels showed a general decline after low-temperature nitriding. Low-temperature liquid nitriding can not only reduce the weight loss due to erosion but also significantly reduce the weight loss rate of interactions, so that the total loss of material decreased evidently. Therefore, 316L stainless steels displayed excellent erosion–corrosion behaviors as a consequence of their highly favorable corrosion resistances and superior wear properties. [ABSTRACT FROM AUTHOR]

ASTRO-H was an X-ray astronomy satellite that the Japan Aerospace Exploration Agency (JAXA) developed to study the evolution of the universe and physical phenomena yet to be discovered. The primary scientific instrument of ASTRO-H was the Soft X-ray Spectrometer (SXS). Its detectors were to be cooled to 50 m K using a complex cryogenic system with a multistage adiabatic demagnetization refrigerator (ADR) developed by the National Aeronautics and Space Administration (NASA), and a cryogenic system developed by Sumitomo Heavy Industries, Ltd. (SHI). SHI’s cryogenic system was required to cool the ADR’s heatsink to 1.3 K or less in orbit for three years or longer. To meet these requirements, SHI developed a hybrid cryogenic system consisting of a liquid helium tank, a 4 K Joule-Thomson cooler, and two two-stage Stirling coolers. ASTRO-H was launched from Tanegashima Space Center on February 17, 2016. The initial operation of the SXS cryogenic system in orbit was completed successfully. The cooling performance was as expected and could have exceeded the lifetime requirement of three years. This paper describes results of ground tests, results of top-off filling of superfluid liquid helium just before launch, and cooling performance in orbit. [ABSTRACT FROM AUTHOR]

Superfluid helium (He II) has been utilized in space projects such as in the X-ray telescope, where it served as the heat sink of adiabatic demagnetization refrigerators. The study of He II boiling under microgravity might contribute to the construction of an important database facilitating the design of future space missions. Therefore, in this study, a visualization experiment of He II boiling was conducted under microgravity conditions by using the drop tower located at ZARM (Center of Applied Space Technology and Microgravity) in Bremen. The ZARM drop tower can provide up to 4.7 s of microgravity conditions in the utilized operation mode. The behavior of thermally induced bubbles during their growth and shrinkage was visualized using two high-speed cameras. A thin manganin wire was utilized as the heater. During the free fall period, the visualized bubble closely approached a steady state. The behavior can be roughly calculated using a simple equation based on kinetic theory. [ABSTRACT FROM AUTHOR]

The sensitivity of earth’s field NMR is greatly increased by the use of a pre-polarizing field B p . When used with short T 1 samples, the field must be decreased rapidly to avoid loss of the pre-polarized magnetization by relaxation. Such a rapid decrease in the field requires rapid discharge (∼10 ms) of a large stored magnetic field energy (∼700 J). In addition, in order that the full pre-polarized magnetization be available for the subsequent pulse sequence, the field discharge should be adiabatic. This requirement is difficult to fulfill in cases where B p is not everywhere parallel to the earth’s field, such as with a large surface coil. Circuitry for rapid and controlled discharge is presented. Simulations and experiments confirm the importance of both of these conditions. [ABSTRACT FROM AUTHOR]

Titanium alloys (Ti6Al4V) have been widely applied in modern aerospace industry as structural components due to their excellent mechanical and physical properties. Meanwhile, the drilling process is essential for machining the assembly holes of Ti6Al4V. However, Ti6Al4V is also a difficult-to-cut material owing to their low thermal conductivity and high chemical reactivity with many tool materials during machining, which easily lead to rapid tool wear, premature tool failure, and poor machining quality. This has attracted wide attention of researchers. In recent years, the rotary ultrasonic-assisted drilling (RUAD) technology, as a novel machining method, has been found to be very effective in the machining of difficult-to-cut materials like nickel alloys and titanium alloys. This paper first introduced an 8-facet drill tool and combined the advantages of RUAD to carry out a study on the drilling of Ti6Al4V under no cooling condition. The experimental results indicated that compared with the common drilling (CD) of Ti6Al4V, in RUAD process with the vibration amplitude of 10 μm, the thrust force, torque, cutting temperature near the drilled hole exit, surface roughness of drilled hole, expansion increment of hole diameter, and burr height of drilled hole exit decreased by 16.79 to 20.2 %, 31.5 to 33.6 %, 18.54 to 21.68 %, 24.87 to 25.36 %, 46.75 to 57.63 %, and 82.27 to 89.18 %, respectively; the excellent chip breakability and removal effect of chip evacuation, superior surface integrity of drilled hole, enhanced tool cutting ability, and prolonged tool life were obtained in RUAD. Furthermore, the experimental results also proved that the drilling technology of RUAD of Ti6Al4V using the 8-facet drill was feasible and the cutting effects were superior. [ABSTRACT FROM AUTHOR]

In this work, we successfully prepare Fe 80 (P, C, B) 20 bulk metallic glasses (BMGs) with the different content of P, C, B by combining fluxing treatment and J-quenching technique, and the effects of the metalloid elements (P, C, B) on the thermal stability and magnetic properties of the present Fe 80 (P, C, B) 20 BMGs are investigated systematically. It is found that the replacements of P or B by C and P by B enhance the thermal stability of Fe 80 (P, C, B) 20 BMGs. The substitutions of B for C or P and C for P result in the increase of both the saturation magnetization and the Curie temperature of Fe 80 (P, C, B) 20 BMGs. [ABSTRACT FROM AUTHOR]

Static satellite-transitions (ST) NMR line shapes from half-integer quadrupolar nuclei could be very informative: they can deliver insight about local motions over a wide range of timescales, and can report on small changes in the local electronic environments as reflected by variations in the quadrupolar parameters. Satellite transitions, however, are typically "invisible" for half-integer quadrupolar nuclei due to their sheer breadth, leading to low signal-to-noise ratio –especially for unreceptive low-gamma or dilute quadrupolar nuclei. Very recently we have introduced a method for enhancing the NMR sensitivity of unreceptive X nuclei in static solids dubbed PROgressive Saturation of the Proton Reservoir (PROSPR), which opens the possibility of magnifying the signals from such spins by repeatedly imprinting frequency-selective X-driven depolarizations on the much more sensitive 1H NMR signal. Here, we show that PROSPR's efficacy is high enough for enabling the detection of static ST NMR for challenging species like 35Cl, 33S and even 17O –all at natural-abundance. The ensuing ST-PROSPR NMR experiment thus opens new approaches to probe ultra-wideline (6–8 MHz wide) spectra. These highly pronounced anisotropies can in turn deliver new vistas about dynamic changes in solids, as here illustrated by tracking ST line shapes as a function of temperature during thermally-driven events. [Display omitted] • PROSPR is a new technique for enhancing the sensitivity of low-γ, dilute nuclei. • This is done by repeatedly depolarizing the 1H spin reservoir. • The experiment detects even broad satellite transitions of nuclei like 17O and 33S. • New opportunities to dynamic characterizations are opened by this experiment. [ABSTRACT FROM AUTHOR]

Structural, electronic and magnetic properties of Heusler compounds CoFeTiGa 1− x Sb x have been studied. X-ray diffraction patterns show that CoFeTiGa 1− x Sb x ( x =0.25, 0.5, 0.75, 1) crystallize into LiMgPdSn-type structure. First-principles calculations indicate that CoFeTiGa 1− x Sb x ( x =0.25, 0.5, 0.75, 1) are half-metal with considerable minority band gaps. The substitution of Sb for Ga gives rise to the spin moments of the compounds, and makes them to be half-metallic ferrimagnets. [ABSTRACT FROM AUTHOR]

A tiny adiabatic-demagnetization refrigerator (T-ADR) has been developed for a commercial superconducting quantum interference device magnetometer [Magnetic Property Measurement System (MPMS) from Quantum Design]. The whole T-ADR system is fit in a cylindrical space of diameter 8.5 mm and length 250 mm, and can be inserted into the narrow sample tube of MPMS. A sorption pump is self-contained in T-ADR, and hence no complex gas handling system is necessary. With the single crystalline Gd3Ga5O12 garnet (~2 g) used as a magnetic refrigerant, the routinely achievable lowest temperature is ~0.56 K. The lower detection limit for a magnetization anomaly is ~1 × 10-7 emu, estimated from fluctuation of the measured magnetization. The background level is ~5 × 10-5 emu below 2 K at H = 100 Oe, which is largely attributable to a contaminating paramagnetic signal from the magnetic refrigerant. [ABSTRACT FROM AUTHOR]

Low temperature (LT) is one of the most important abiotic stresses that can significantly reduce crop yield. To gain insight into how Spirulina responds to LT stress, comprehensive physiological and proteomic analyses were conducted in this study. Significant decreases in growth and pigment levels as well as excessive accumulation of compatible osmolytes were observed in response to LT stress. An isobaric tag for relative and absolute quantitation (iTRAQ)-based quantitative proteomics approach was used to identify changes in protein abundance in Spirulina under LT. A total of 3,782 proteins were identified, of which 1,062 showed differential expression. Bioinformatics analysis indicated that differentially expressed proteins that were enriched in photosynthesis, carbohydrate metabolism, amino acid biosynthesis, and translation are important for the maintenance of cellular homeostasis and metabolic balance in Spirulina when subjected to LT stress. The up-regulation of proteins involved in gluconeogenesis, starch and sucrose metabolism, and amino acid biosynthesis served as coping mechanisms of Spirulina in response to LT stress. Moreover, the down-regulated expression of proteins involved in glycolysis, TCA cycle, pentose phosphate pathway, photosynthesis, and translation were associated with reduced energy consumption. The findings of the present study allow a better understanding of the response of Spirulina to LT stress and may facilitate in the elucidation of mechanisms underlying LT tolerance. [ABSTRACT FROM AUTHOR]

The inspection of simplified fabrication and/or processing routes in order to produce materials with attractive magnetocaloric properties is of paramount importance for the development of environmentally friendly magnetic cooling technology. In this work, we have made use of the melt-spinning technique to obtain directly single-phase Y 2 Fe 17 polycrystalline ribbons avoiding any high-temperature annealing for phase consolidation and homogenization. The melt-spun ribbons, with hexagonal Th 2 Ni 17 -type crystal structure, exhibit a moderate maximum value of the magnetic entropy change, |Δ S M peak | = 2.4(4.4) J kg −1 K −1 under an applied magnetic field change of 2(5) T. Although these values are similar to those for the bulk alloy, the Δ S M ( T ) curves are manifestly broader, thus giving rise to an expansion of the working temperature range and the enhancement of about 15% in the refrigerant capacity. We also show that the magnetic field dependence of |Δ S M peak | at T = T C follows a H 2/3 power-law. [ABSTRACT FROM AUTHOR]

We present a magnetic cooling chain designed to have a continuous heat sink below 50 mK. It has been focused on providing a cryogen-free and autonomous operation for the users. The challenge is to provide two levels of continuous cooling in order to control the heat balance on the coldest stage. Designed for scientific research and high sensitivity cryogenic detectors applications, the prototype has been validated with a kinetic inductance detectors array. A completely autonomous operation of the cryogenics system from 300 K down to 100 mK has been validated. [ABSTRACT FROM AUTHOR]

Micro-X is a NASA funded, rocket borne X-ray imaging spectrometer that uses transition edge sensors (TESs) to do high-resolution microcalorimetry. The TESs are cooled by an adiabatic demagnetization refrigerator, whose salt pill functions as a heat sink for the detectors. We have made a thermal model of the cryostat with SPICE for the purposes of understanding its behavior at low temperatures. Implementing modifications based on this model has further allowed us to cool the system down to a lower temperature than had previously been accessible and to improve its low-temperature hold time. These modifications include a variety of schemes for power through heat sinks and tweaking the conductance between the cold baths and the refrigerated hardware. We present an overview of the model and its constituent parameters, information about thermal modifications, and a summary of results from thermal tests of the entire system. [ABSTRACT FROM AUTHOR]

We have been developing a compact adiabatic demagnetization refrigerator, keeping ground application and future missions in mind. A salt pill fabricated in-house, a superconducting magnet with a passive magnetic shield around it, and a mechanical heat switch are mounted in a dedicated helium cryostat. The detector stage temperature is regulated by PID control of the magnet current, with a $$\mathrm{d}I/\mathrm{d}t$$ term added to compensate the temperature rise due to parasitic heat. The temperature fluctuation of the detector stage is 1-2 $$\upmu $$ Krms, and the hold time was extended by about 15 % thanks to the $$\mathrm{d}I/\mathrm{d}t$$ term. Bundle shields of the harnesses between the cryostat and the analog electronics boxes were connected to the chassis at both ends, and the analog electronics boxes were grounded to the cryostat through the bundle shields. This reduced the readout noise to 16 pA/ $$\sqrt{\mathrm{Hz}}$$ in the 10-60 kHz range. Using this system, an energy resolution of 3.8 $$\pm $$ 0.2 eV (FWHM) was achieved at 5.9 keV. [ABSTRACT FROM AUTHOR]

A 3-stage adiabatic demagnetization refrigerator (ADR) (Shirron et al., 2012) is used on the Soft X-ray Spectrometer instrument (Mitsuda et al., 2010) on Astro-H (Takahashi et al., 2010) [3] to cool a 6 × 6 array of X-ray microcalorimeters to 50 mK. The ADR is supported by a cryogenic system (Fujimoto et al., 2010) consisting of a superfluid helium tank, a 4.5 K Joule–Thomson (JT) cryocooler, and additional 2-stage Stirling cryocoolers that pre-cool the JT cooler and cool radiation shields within the cryostat. The ADR is configured so that it can use either the liquid helium or the JT cryocooler as its heat sink, giving the instrument an unusual degree of tolerance for component failures or degradation in the cryogenic system. The flight detector assembly, ADR and dewar were integrated into the flight dewar in early 2014, and have since been extensively characterized and calibrated. This paper summarizes the operation and performance of the ADR in all of its operating modes. [ABSTRACT FROM AUTHOR]

The performance of a fast thermal response miniature Adiabatic Demagnetisation Refrigerator (ADR) is presented. The miniature ADR is comprised of a fast thermal response Chromium Potassium Alum (CPA) salt pill, two superconducting magnets and unconventionally, a single crystal tungsten magnetoresistive (MR) heat switch. The development of this ADR is a result of the ongoing development of a continuously operating millikelvin cryocooler (mKCC), which will use only magnetoresistive heat switches. The design and performance of the MR heat switch developed for the mKCC and used in the miniature ADR is presented in this paper; the heat switch has a measured Residual Resistivity Ratio of 32,000 ± 3000 and an estimated switching ratio (on thermal conductivity divided by the off thermal conductivity) of 15,200 at 3.6 K and 38,800 at 0.2 K when using a 3 T magnetic field. The performance of the miniature ADR operating from a 3.6 K bath is presented, demonstrating that a complete cycle (magnetisation, cooling to the bath and demagnetisation) can be accomplished in 82 s. A magnet current step test, conducted when the ADR is cold and fully demagnetised, has shown the thermal response of the ADR to be sub-second. The measured hold times of the ADR with just parasitic heat load are given, ranging from 3 min at 0.2 K with 13.14 μW of parasitics, to 924 min at 3 K with 4.55 μW of parasitics. The cooling power has been measured for operating temperatures in the range 0.25–3 K by applying an additional heat load to the ADR via a heater, in order to reduce the hold time to 3 min (i.e. approximately double the recycle time); the maximum cooling power of the miniature ADR (in addition to parasitic load) when operating at 250 mK is 20 μW, which increases to 45 μW at 300 mK and continues to increase linearly to nearly 1.1 mW at 3 K. To conclude, the predicted performance of a tandem continuous ADR utilising two of the miniature ADRs is presented. [ABSTRACT FROM AUTHOR]

The adiabatic demagnetization refrigerator (ADR) system in this paper is composed of a conduction-cooled current cycling high-temperature superconducting (HTS) magnet system, a magnetic bed assembly, its heat exchange parts and an auxiliary precooling stage (a commercial GM cryocooler and a liquid nitrogen vessel). The whole magnetic refrigeration system including the conduction-cooled HTS magnet is cooled by the precooling stage to absorb the rejection heat of the ADR cycle. The packed bed type magnetic bed consists of tiny irregular powders of Dy 0.9 Gd 0.1 Ni 2 enclosed in a thin walled stainless steel container (22.2 mm in O.D., 0.3 mm in thickness and 40.0 mm in height). The precooled heat transfer fluid (helium) travels through the magnetic material when heat rejection is required; otherwise the helium stagnates within its pores (pseudo-adiabatic process). Flow of the heat transfer fluid substitutes for the function of a traditional heat switch, creating, essentially, a forced-convection type heat switch. The magnetic bed assembly is periodically magnetized and demagnetized at the center of the conduction-cooled HTS magnet which can stably generate both strong and alternating magnetic field from 0 T to 3.0 T (0–130 A) with an average ramp rate of 0.24 T s −1 . The cooling capacities of the ADR system at 20 K which is the normal boiling point (NBP) of hydrogen, are 11.1 J cycle −1 , 6.3 J cycle −1 and 1.9 J cycle −1 when the temperature spans are 1 K, 2 K and 3 K, respectively. We describe the detailed construction of the ADR system and discuss the test results with the operational parameters (the entrained helium pressure, the mass flow rate of helium and the operating temperature span) in the 20 K region. [ABSTRACT FROM AUTHOR]

Implications of the breakdown and oxidation processes for the magnetic properties of finegrained titanomagnetites are theoretically studied in the model of two-phase nanoparticle system. It is shown that the decomposition of titanomagnetites is accompanied by the increase in the blocking temperature, coercive force, spontaneous saturation magnetization, and chemical magnetization, whereas the remanent chemical magnetization behaves nonmonotonically and may undergo self-reversal. The single-phase oxidation of titanomagnetites reduces the coercive force and saturation magnetization and thus leads to the growth in chemical magnetization. [ABSTRACT FROM AUTHOR]

The Background Limited Infrared Submillimeter Spectrometer (BLISS) is an instrument proposed for SPICA, the Japanese–European space-borne telescope mission under study for a possible launch in the next decade. The BLISS concept is a suite of aluminum spectrometer modules totaling ∼10 kg cooled to 50 mK. Cooling this ambitious instrument with high-duty cycle within the stringent heat-rejection allocations envisioned for SPICA is a challenge. We have developed a solution consisting of two stages: (1) a continuous 300 mK intercept stage provided by two 3He sorption coolers operated sequentially, and (2) a 50 mK adiabatic demagnetization refrigerator (ADR) operated in single-shot mode. We have built a prototype cooler and demonstrated it in a dedicated SPICA-like thermal testbed with regulated stages enabling measurement of rejected heat at 1.7 K and 4.5 K. The approach offers lower mass than a dual-stage ADR, and lower rejected power to 1.7 K and 4.5 K than a comparable single-shot 300 mK system, while insuring a high duty cycle. As a demonstration of feasibility for SPICA and future cryogenic missions, we show long-term cooling with flight-like parasitics at 50 mK and 300 mK requiring only 3 mW and 8 mW rejected at 1.7 K and 4.5 K, respectively. [ABSTRACT FROM AUTHOR]

We report a new design of an AC magnetic susceptometer compatible with the Physical Properties Measurement System (PPMS) by Quantum Design, as well as with its adiabatic demagnetization refrigerator option. With the elaborate compact design, the susceptometer allows simple and quick sample mounting process. The high performance of the susceptometer down to 0.1 K is demonstrated using several superconducting and magnetic materials. This susceptometer provides a method to quickly investigate qualities of a large number of samples in the wide temperature range between 0.1 and 300 K. [ABSTRACT FROM AUTHOR]

It is shown that a sequence of processes is possible in ferroelectrics, analogous to those which occur when a saturated paramagnetic material is cooled under adiabatic depolarization conditions, and it becomes a ferromagnetic material. The conditions required to construct a dielectric calorimeter with an extremely high sensitivity of 0.04 eV/Hz are considered. [ABSTRACT FROM AUTHOR]

The electrocaloric response of KNbO 3 is calculated using a first-principles based effective-Hamiltonian. Both indirect and direct molecular dynamics simulations are used to determine the adiabatic temperature change as a function of temperature and applied electric field. Both the magnitude of the electrocaloric response, Δ T max , and the temperature where the maximum is observed, T * , are comparable for both molecular dynamics approaches. The results are well represented by a simple second-order regression. [ABSTRACT FROM AUTHOR]

The spin-1/2 Ising octahedron and dodecahedron with a unique antiferromagnetic interaction display an outstanding magnetization jump at zero magnetic field, which consequently leads to a giant magnetocaloric effect during the adiabatic demagnetization. In the present work we report temperature dependences of two basic magnetocaloric response functions: the isothermal entropy change and the adiabatic change of temperature. It is shown that the Ising octahedron and dodecahedron generally exhibit a large negative isothermal entropy change upon increase of the magnetic field, which serves in evidence of their cooling performance. [ABSTRACT FROM AUTHOR]

A mechanical cryogenic heat switch has been developed using a commercially available stepper motor and control electronics. The motor requires 4 leads, each carrying a maximum, pulsed current of 0.5 A. With slight modifications of the stepper motor, the switch functions reliably in vacuum at temperatures between 300 K and 4 K. The switch generates a clamping force of 262 N at room temperature. At 4 K it achieves an "on state" thermal conductance of 5.04 mW/K and no conductance in the "off state." The switch is optimized for cycling an adiabatic demagnetization refrigerator. [ABSTRACT FROM AUTHOR]

• We designed the cooling system from room temperature to about 1 K for XRISM Resolve. • Based on ASTRO-H (Hitomi) SXS lessons learned, changes on the design are adopted and new tests are planned. • The major design changes include an aperture baffle, an eddy current damper and a new vibration isolation system. The X-ray Imaging and Spectroscopy Mission (XRISM) is a recovery mission of ASTRO-H (Hitomi) launched in 2016. The Resolve instrument on the XRISM is an 6 × 6 array of silicon-thermistor microcalorimeters cooled down to 50 mK combined with a 5.6 m focal length X-ray telescope. Its design inherits that of the Soft X-ray Spectrometer (SXS) onboard ASTRO-H that demonstrated high resolution spectroscopy of the X-ray microcalorimeters by observing astronomical objects and providing superb resolution spectra. The cooling chain of the Resolve consists of a 3-stage adiabatic demagnetization refrigerator (ADR), a Joule-Thomson cooler, ~ 30 L superfluid helium, four Stirling coolers and a vacuum vessel or a dewar. Design of the Resolve cooling system is basically the same as that in the SXS but several changes are adopted based on lessons learned. This paper describes mainly the cooling system from room temperature to about 1 K providing the ADR heat sink. Major changes include an aperture baffle for micrometeoroid and orbital debris protection and optical light reduction, an eddy current damper to slow a gate valve opening, a new vibration isolation system with launch-locks. [ABSTRACT FROM AUTHOR]