Magnetic hardening mechanisms in Nd-Fe-B nanocrystalline material

Microstructural and magnetic measurements of the evolution by heat treatment of initially amorphous Nd16Fe76B8 alloys prepared by melt spinning are presented. Evidence of magnetic hardening above a threshold temperature induced by magnetic isolation of the Nd2Fe14B grains is provided. A thermodynamic and kinetic explanation of local melting of the intergranular nanostructured Nd¿rich eutectic phase at temperatures below 900 K based on capillary effects is presented. A subsequent Ostwald ripening process moves Nd to wet intimately the hard magnetic grains, becoming, on cooling, a real paramagnetic isolating thin film (~2.5 nm). By using a simple analogy, it is shown that the switching magnetization field in a single¿domain crystal can be drastically affected through the exchange coupling to neighboring grains with different orientation of the easy axis. This effect should be important enough to reinforce the coercive field of polycrystalline hard magnetic materials and explains the observed enhancement from 0.9 to 1.9 T.

Martensitic phase transformation in rapidly solidified Mn50Ni40In10 alloy ribbons

Heusler alloy Mn50Ni40In10 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 MS=213 K, Mf=173 K, AS=222 K, and Af=243 K. Austenite phase shows a cubic L21 structure (a=0.6013(3) nm at 298 K and a Curie point of 311 K), transforming into a modulated fourteen-layer modulation monoclinic martensite

Microstructure and magnetic properties of Ni50 Mn37 Sn13 Heusler alloy ribbons

The Heusler alloy Ni50 Mn37 Sn13 was successfully produced as ribbon flakes of thickness around 7-10 μm 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 MS =218 K, Mf =207 K, AS =224 K, and Af =232 K; the thermal hysteresis of the transformation is 15 K. Ferromagnetic L 21 bcc austenite phase shows a Curie point of 313 K, with cell parameter a=0.5971 (5) nm at 298 K, transforming into a modulated 7M orthorhombic martensite with a=0.6121 (7) nm, b=0.6058 (8) nm, and c=0.5660 (2) nm, at 150 K

Ferromagnetic shape memory alloys: structural and thermal properties

The most extensively studied Heusler alloys are those based on the Ni-Mn-Ga system. However, to overcome the high cost of Gallium and the usually low martensitic transformation temperature, the search for Ga-free alloys has been recently attempted, particularly, by introducing In, Sn or Sb. In this work, two alloys (Mn50Ni35.5In14.5 and Ni50Mn35In15) have been obtained by melt spinning. We outline their structural and thermal behaviour. Mn50Ni35.5In14.5 alloy has the transformation above room temperature whereas Ni50Mn35In15 does not have this transformation in the temperature range here analyzed

Wages and prices in early Catalan industrialisation

[eng] Catalonia was the only Mediterranean region among the early followers of the British Industrial Revolution in the second third of the nineteenth century. The roots of this industrialisation process can be traced back to the seventeenth and eighteenth centuries when the Catalan economy became successfully integrated in international trade and the region enjoyed an intensification of its agrarian and proto-industrial activities. These capitalist developments were subsequently reinforced by a successful printed calico manufacturing business concentrated in the city of Barcelona. Although the factory system was largely adopted by the cotton industry in the 1840s, the diffusion of the spinning jenny had occurred earlier in the 1790s. In this paper, in line with Allen (2009a, 2009b), we explore whether relative factor prices played a role in the widespread adoption of the spinning jenny in Catalonia.

Wages and prices in early Catalan industrialisation

[eng] Catalonia was the only Mediterranean region among the early followers of the British Industrial Revolution in the second third of the nineteenth century. The roots of this industrialisation process can be traced back to the seventeenth and eighteenth centuries when the Catalan economy became successfully integrated in international trade and the region enjoyed an intensification of its agrarian and proto-industrial activities. These capitalist developments were subsequently reinforced by a successful printed calico manufacturing business concentrated in the city of Barcelona. Although the factory system was largely adopted by the cotton industry in the 1840s, the diffusion of the spinning jenny had occurred earlier in the 1790s. In this paper, in line with Allen (2009a, 2009b), we explore whether relative factor prices played a role in the widespread adoption of the spinning jenny in Catalonia.

Wages and prices in early Catalan industrialisation

[eng] Catalonia was the only Mediterranean region among the early followers of the British Industrial Revolution in the second third of the nineteenth century. The roots of this industrialisation process can be traced back to the seventeenth and eighteenth centuries when the Catalan economy became successfully integrated in international trade and the region enjoyed an intensification of its agrarian and proto-industrial activities. These capitalist developments were subsequently reinforced by a successful printed calico manufacturing business concentrated in the city of Barcelona. Although the factory system was largely adopted by the cotton industry in the 1840s, the diffusion of the spinning jenny had occurred earlier in the 1790s. In this paper, in line with Allen (2009a, 2009b), we explore whether relative factor prices played a role in the widespread adoption of the spinning jenny in Catalonia.

Wages and prices in early Catalan industrialisation

Catalonia was the only Mediterranean region among the early followers of the British Industrial Revolution in the second third of the nineteenth century. The roots of this industrialisation process can be traced back to the seventeenth and eighteenth centuries when the Catalan economy became successfully integrated in international trade and the region enjoyed an intensification of its agrarian and proto-industrial activities. These capitalist developments were subsequently reinforced by a successful printed calico manufacturing business concentrated in the city of Barcelona. Although the factory system was largely adopted by the cotton industry in the 1840s, the diffusion of the spinning jenny had occurred earlier in the 1790s. In this paper, in line with Allen (2009a, 2009b), we explore whether relative factor prices played a role in the widespread adoption of the spinning jenny in Catalonia.

Wages and prices in early Catalan industrialisation

Catalonia was the only Mediterranean region among the early followers of the British Industrial Revolution in the second third of the nineteenth century. The roots of this industrialisation process can be traced back to the seventeenth and eighteenth centuries when the Catalan economy became successfully integrated in international trade and the region enjoyed an intensification of its agrarian and proto-industrial activities. These capitalist developments were subsequently reinforced by a successful printed calico manufacturing business concentrated in the city of Barcelona. Although the factory system was largely adopted by the cotton industry in the 1840s, the diffusion of the spinning jenny had occurred earlier in the 1790s. In this paper, in line with Allen (2009a, 2009b), we explore whether relative factor prices played a role in the widespread adoption of the spinning jenny in Catalonia.

A Be-type star with a black-hole companion

Stellar-mass black holes have all been discovered through X-ray emission, which arises from the accretion of gas from their binary companions (this gas is either stripped from low-mass stars or supplied as winds from massive ones). Binary evolution models also predict the existence of black holes accreting from the equatorial envelope of rapidly spinning Be-type stars (stars of the Be type are hot blue irregular variables showing characteristic spectral emission lines of hydrogen). Of the ~80 Be X-ray binaries known in the Galaxy, however, only pulsating neutron stars have been found as companions. A black hole was formally allowed as a solution for the companion to the Be star MWC 656 (also known as HD 215227), although that was based on a single radial velocity curve of the Be star, a mistaken spectral classification and rough estimates of the inclination angle. Here we report observations of an accretion disk line mirroring the orbit of the Be star. This, together with an improved radial velocity curve of the Be star through fitting sharp Fe II profiles from the equatorial disk, and a refined Be classification (to that of a B1.5-B2 III star), reveals a black hole of 3.8 to 6.9 solar masses orbiting MWC 656, the candidate counterpart of the gamma-ray source AGL J2241+4454. The black hole is X-ray quiescent and fed by a radiatively inefficient accretion flow giving a luminosity less than 1.6 x 10-7 times the Eddington luminosity. This implies that Be binaries with black-hole companions are difficult to detect by conventional X-ray surveys.

All-sky search algorithms for monochromatic signals in bar gravitational wave detector data

In this paper we design and develop several filtering strategies for the analysis of data generated by a resonant bar gravitational wave (GW) antenna, with the goal of assessing the presence (or absence) therein of long-duration monochromatic GW signals, as well as the eventual amplitude and frequency of the signals, within the sensitivity band of the detector. Such signals are most likely generated in the fast rotation of slightly asymmetric spinning stars. We develop practical procedures, together with a study of their statistical properties, which will provide us with useful information on the performance of each technique. The selection of candidate events will then be established according to threshold-crossing probabilities, based on the Neyman-Pearson criterion. In particular, it will be shown that our approach, based on phase estimation, presents a better signal-to-noise ratio than does pure spectral analysis, the most common approach.

Current Sheet Regulation of Solar Near-relativistic Electron Injection Histories

We present a sample of three large near-relativistic (>50 keV) electron events observed in 2001 by both the ACE and the Ulysses spacecraft, when Ulysses was at high-northern latitudes (>60◦) and close to 2 AU. Despite the large latitudinal distance between the two spacecraft, electrons injected near the Sun reached both heliospheric locations. All three events were associated with large solar flares, strong decametric type II radio bursts and accompanied by wide (>212◦) and fast (>1400 km s−1) coronal mass ejections (CMEs). We use advanced interplanetary transport simulations and make use of the directional intensities observed in situ by the spacecraft to infer the electron injection profile close to the Sun and the interplanetary transport conditions at both low and high latitudes. For the three selected events, we find similar interplanetary transport conditions at different heliolatitudes for a given event, with values of the mean free path ranging from 0.04 AU to 0.27 AU. We find differences in the injection profiles inferred for each spacecraft. We investigate the role that sector boundaries of the heliospheric current sheet (HCS) have on determining the characteristics of the electron injection profiles. Extended injection profiles, associated with coronal shocks, are found if the magnetic footpoints of the spacecraft lay in the same magnetic sector as the associated flare, while intermittent sparse injection episodes appear when the spacecraft footpoints are in the opposite sector or a wrap in the HCS bounded the CME structure.

Current Sheet Regulation of Solar Near-Relativistic Electron Injection Histories

We present a sample of three large near-relativistic (>50 keV) electron events observed in 2001 by both the ACE and the Ulysses spacecraft, when Ulysses was at high-northern latitudes (>60°) and close to 2 AU. Despite the large latitudinal distance between the two spacecraft, electrons injected near the Sun reached both heliospheric locations. All three events were associated with large solar flares, strong decametric type II radio bursts and accompanied by wide (>212°) and fast (>1400 km s-1) coronal mass ejections (CMEs). We use advanced interplanetary transport simulations and make use of the directional intensities observed in situ by the spacecraft to infer the electron injection profile close to the Sun and the interplanetary transport conditions at both low and high latitudes. For the three selected events, we find similar interplanetary transport conditions at different heliolatitudes for a given event, with values of the mean free path ranging from 0.04 AU to 0.27 AU. We find differences in the injection profiles inferred for each spacecraft. We investigate the role that sector boundaries of the heliospheric current sheet (HCS) have on determining the characteristics of the electron injection profiles. Extended injection profiles, associated with coronal shocks, are found if the magnetic footpoints of the spacecraft lay in the same magnetic sector as the associated flare, while intermittent sparse injection episodes appear when the spacecraft footpoints are in the opposite sector or a wrap in the HCS bounded the CME structure.

Off-Diagonal Magnetoimpedance Dependence of Magnetostriction and Anisotropy in Co-Based and Fe-Based Amorphous Ribbons

The object of this work is the comparison of domain structure and off-diagonal magnetoimpedance effect in amorphous ribbons with different magnetostriction coefficient. The Co66Fe4Ni1Si15B14 and Fe80B20 samples were obtained by melt-spinning. During the quenching procedure a 0.07 T transverse magnetic field was applied to some of the samples. Domain patterns obtained by the Bitter technique confirm that the differences on the samples are related to the different anisotropy and magnetostriction coefficient, and the quenching procedure. Small changes on the anisotropy distribution and the magnetostriction coefficient can be detected by the off-diagonal impedance spectra as a consequence of the different permeability values of the samples