Heusler alloy Mn 50 Ni 40 In 10 was produced as preferentially textured ribbon flakes by melt spinning, finding the existence of martensitic-austenic transformation with both phases exhibiting ferromagnetic ordering. A microcrystalline three-layered microstructure of ordered columnar grains grown perpendicularly to ribbon plane was formed between two thin layers of smaller grains. The characteristic temperatures of the martensitic transformation were M S = 213 K, M f = 173 K, A S = 222 K, and A f = 243 K. Austenite phase shows a cubic L2 1 structure ͑a = 0.6013͑3͒ nm at 298 K and a Curie point of 311 K͒, transforming into a modulated fourteen-layer modulation monoclinic martensite. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2827179͔Since Sutou et al.1 reported the occurrence of martensitic transformation in the ferromagnetic Heusler system Ni 50 Mn 50−x In x , considerable attention has been dedicated to study magnetism and magnetic shape memory effect, [2][3][4] magnetic entropy change, [4][5][6][7][8] and magnetotransport properties 9-11 of these alloys. Nevertheless, ferromagnetism in both phases is only observed in the narrow composition range of 15ഛ x ഛ 16 2 . The characteristic temperatures of the reversible first order structural transformation between both phases, referred as martensitic and austenitic starting and finish temperatures ͑i.e., M S , M f , A S , and A f , respectively͒, strongly vary upon small changes in the chemical composition. The crystal structure of austenite and martensite depends on the composition, 2,4 and the transformation can be also induced by applying a magnetic field.2-4 Additionally, a large inverse and direct magnetocaloric effect has been measured in Ni 50 Mn 34 In 16 .6-8 Ni-Mn-In Heusler alloys are therefore of significant prospective importance for applications in both magnetically driven actuators due to magnetic shape memory effect and as working substances in magnetic refrigeration technology.Until now, the investigated alloys are usually bulk polycrystals obtained by arc or induction melting followed by a high temperature annealing, [1][2][3][4][5][6][7][8]10 or single crystals grown by Czochralski method.9,11 Present investigation was carried out to employ rapid quenching by melt spinning to produce MnNi-In Heusler alloys. This technique offers two potential advantages for the fabrication of these magnetic shape memory alloys: the avoiding, or reduction, of the annealing to reach a homogeneous single phase alloy, and the synthesis of highly textured polycrystalline ribbons. Ribbon shape can be also appropriate for use in practical devices. We fabricated the alloy Mn 50 Ni 40 In 10 by melt spinning. Its valence electronic concentration per atom e / a is 7.801, allowing the existence of martensite-austenite transformation with both phases exhibiting ferromagnetic ordering, opening its potential use as a magnetic shape memory alloy. 3 We report in this letter a preliminary characterization of the microstructural features and magnetic behavior.As-cast pel...

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The Heusler alloy Ni 50 Mn 37 Sn 13 was successfully produced as ribbon flakes of thickness around 7-10 m melt spinning. Fracture cross section micrographs in the ribbon show the formation of a microcrystalline columnarlike microstructure, with their longer axes perpendicular to the ribbon plane. Phase transition temperatures of the martensite-austenite transformation were found to be M S = 218 K, M f = 207 K, A S = 224 K, and A f = 232 K; the thermal hysteresis of the transformation is 15 K. Ferromagnetic L2 1 bcc austenite phase shows a Curie point of 313 K, with cell parameter a = 0.5971͑5͒ nm at 298 K, transforming into a modulated 7M orthorhombic martensite with a = 0.6121͑7͒ nm, b = 0.6058͑8͒ nm, and c = 0.5660͑2͒ nm, at 150 K. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2832330͔Ferromagnetic shape memory alloys ͑FSMA͒ are of considerable interest because of their exceptional magnetoelastic properties.1-3 The shape memory effect can not only be controlled by changing the temperature, as it occurs in traditional shape memory alloys, but also by varying the magnetic field up to moderate field values. The latter makes them of noteworthy interest for developing new thermal or magnetically driven actuators. 4Among the Heusler alloys that exhibit magnetic shape memory effect, the most extensively studied are those of the Ni-Mn-Ga system. However, to overcome some of the problems related to practical application, such as the high cost of gallium and the low martensitic transformation temperature that they usually present, the search for Ga-free alloys has been recently attempted. Martensitic transformation in ferromagnetic Heusler Ni 50 Mn 50−x Sn x alloys with 10ഛ x ഛ 16.5 was first reported by Sutou et al. 5 Later, Krenke et al. studied phase transformations and magnetic and magnetocaloric properties of the Ni 50 Mn 50−x Sn x alloy series with 5 ഛ x ഛ 25. 6,7 Samples with x = 0.13 and 0.15 are ferromagnetic in the martensitic state undergoing a first order martensitic-austenitic structural transition at a temperature below the respective Curie points of both phases. At room temperature, the alloy with x = 0.13 is martensitic, and the martensite-austenite transformation occurs around room temperature. Brown et al. 8 12 They report magnetic entropy changes up to 10.4 J / kg K at 10 kOe for x = 7. Ni-Mn-Sn system is, therefore, of prospective importance as FSMA and as promising magnetic refrigerant alloy. In all these cases, alloys were produced as bulk polycrystalline samples.In this work we produced, as far as we know for the first time, Ni-Mn-Sn alloys by rapid solidification. This procedure offers several potential advantages for the fabrication of the shape memory materials such as avoiding the homogenization annealing step to reach a single phase alloy and the synthesis of highly textured polycrystalline samples. Moreover, ribbon shape is appropriate for direct use in practical devices. In view of its interesting properties, 6,7 we have selected the alloy Ni 50 Mn 37 Sn 13 and studied its microstr...

Magnification bias is a gravitational lensing effect that is normally overlooked because it is considered sub-optimal in comparison with the lensing shear. Thanks to the demonstrated optimal characteristics of the sub-millimetre galaxies (SMGs) for lensing analysis, in this work we were able to measure the magnification bias produced by a sample of QSOs acting as lenses, 0.2 13.6−0.4+0.9, also confirmed by the mass density profile analysis (M200c∼ 1014 M⊙). These mass values indicate that we are observing the lensing effect of a cluster size halo signposted by the QSOs, as in previous studies of the magnification bias. Moreover, we were able to estimate the lensing convergence, κ(θ), for our magnification bias measurements down to a few kpcs. The derived mass density profile is in good agreement with a Navarro-Frank-White (NFW) profile. We also attempt an estimation of the halo mass and the concentration parameters, obtaining MNFW=1.0+0.4−0.2×1014 M⊙ and C=3.5−0.3+0.5. This concentration value is rather low and it would indicate that the cluster halos around these QSOs are unrelaxed. However, higher concentration values still provides a compatible fit to the data.

Core-collapse supernovae are among the most magnificent events in the observable universe. They produce many of the chemical elements necessary for life to exist and their remnants-neutron stars and black holes-are interesting astrophysical objects in their own right. However, despite millennia of observations and almost a century of astrophysical study, the explosion mechanism of core-collapse supernovae is not yet well understood.

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Highly hexagonally ordered CoPd alloy nanowire arrays were synthesized through electrochemical deposition techniques into the nanopores of anodic alumina membranes used as templates. Two different electrolytes were used for this purpose, one with pH = 4.1 and the other with pH = 7. Under applying different electrodeposition parameters and by adjusting both, the current density and the electrolyte composition, it could be possible make to vary the composition of CoPd alloy nanowires in a wide range. Their composition and morphology were investigated by SEM and EDX. The magnetic properties of the nanowires array have been measured with a VSM as a function of the temperature, ranging from RT down to 50 K, for different CoPd alloy nanowires composition. Also, the temperature influence on the reversible-irreversible magnetization processes related with the magnetization reversal of the CoPd nanowires array has been analyzed by first order reversal curve (FORC) method.

Thermal and field-induced martensite-austenite transition was studied in melt spun Ni 50.3 Mn 35.3 Sn 14.4 ribbons. Its distinct highly ordered columnarlike microstructure normal to ribbon plane allows the direct observation of critical fields at which field-induced and highly hysteretic reverse transformation starts ͑H = 17 kOe at 240 K͒, and easy magnetization direction for austenite and martensite phases with respect to the rolling direction. Since martensitic transformation from cubic L2 1 -type crystal structure to orthorhombic four-layered martensite ͑4O͒ was observed in Heusler alloys of the ternary system Ni 50 Mn 50−x Sn x , 1 important attention has been devoted to investigate structural transformations, magnetoelastic and magnetocaloric properties in these Ga-free ferromagnetic shape memory alloys. [2][3][4][5][6][7][8][9][10][11] The studies concluded that these materials are prospective for the development of magnetically driven actuators and working substances for magnetic refrigeration. The occurrence of ferromagnetism in both phases has been only found in the narrow composition range of 13ഛ x ഛ 15, 2 and the different magnetization values between martensite and austenite phases leads to a large magnetocaloric effect around the martensitic transition. 7,9 Their crystal structures, as well as the characteristic temperatures of its mutual reversible transformation ͑the starting and finish martensitic and austenitic temperatures, M S , M f , A S , and A f , respectively͒, are very sensitive to small variations in the valence electron concentration per atom e / a, 2,3 and consequently to chemical composition and also depends on the magnetic applied field. The magnetic field can also induce a reverse structural transformation as has been unambiguously demonstrated studying field dependence of x-ray diffraction ͑XRD͒ profiles in bulk polycrystalline Ni 50 Mn 36 Sn 14 alloys, 6 where a field higher than 50 kOe was required to induce around A S a complete phase transition.Rapid quenching by melt spinning offers two potential advantages for the fabrication of these magnetic shape memory alloys: the avoiding, or reduction, of the annealing to reach a homogeneous single phase alloy, and the synthesis of highly textured polycrystalline ribbons. In addition, ribbon shape can be also more appropriate for use in practical devices. Recently, we reported that it was an effective singlestep production process for obtaining Ni 50 Mn 37 Sn 13 ribbons with homogenous chemical composition and strongly ordered microstructure. 12 In this letter, we report on the thermal and magnetic field-induced martensite-austenite transformation, microstructural, and magnetic properties of Ni 50.3 Mn 35.3 Sn 14.4 alloy ribbons.Ribbon flakes of width about 1.5-2.0 mm and length of 6 -7 mm were produced by melt spinning in argon atmosphere at a wheel linear speed of 48 ms −1 starting from arc melted alloys prepared from highly pure elements ͑Ͼ99.9% ͒. Samples were annealed in high vacuum for 2 h at 1073 K. Annealing was followed by wate...