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See detailMagnetic and transport properties of HoMnO3 monocrystals
Radulov, Iliya; Lovchinov, Vassil; Dimitrov, Dimitar et al

in Journal of Optoelectronics and Advanced Materials [= JOAM] (2009), 11

This paper presents results from measurements of the magnetization, specific heat and dielectric constant, and their temperature and magnetic field dependence, for HoMnO3 single crystals. The results are ... [more ▼]

This paper presents results from measurements of the magnetization, specific heat and dielectric constant, and their temperature and magnetic field dependence, for HoMnO3 single crystals. The results are discussed in the framework of existing data on magnetic symmetries and the interactions between the Mn-spins, the rare earth moments, and the lattice. From the resulting data, the magnetic phase diagram of HoMnO3 was built. [less ▲]

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See detailMagnetic anisotropy of U2Pd2In
Prokes, Karel; Nakotte, Heinz; Havela, Ladislav et al

in Physica B: Condensed Matter (1996), 223-224

Magnetic susceptibility studies of the U2Pd2In single crystal show that in the paramagnetic state larger χ-values are found for field along the basal plane than along the c-axis. However, below TN = 37 K ... [more ▼]

Magnetic susceptibility studies of the U2Pd2In single crystal show that in the paramagnetic state larger χ-values are found for field along the basal plane than along the c-axis. However, below TN = 37 K, where U-moments form a non-collinear magnetic structure within the basal plane, a cross-over of the two χ-branches occurs. The single crystal results may explain the origin of the exotic magnetization results obtained on powder samples. [less ▲]

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See detailMagnetic behaviour of soft ferromagnetic alloys attached to bulk (RE)BCO superconductors
Philippe, Matthieu ULg; Fagnard, Jean-François ULg; Dennis, Anthony et al

Poster (2012, October)

Bulk (RE)BCO materials can be used potentially as powerful permanent magnets. The magnetic field distribution around a bulk HTS magnet, however, is strongly non-uniform (conic profile predicted by the ... [more ▼]

Bulk (RE)BCO materials can be used potentially as powerful permanent magnets. The magnetic field distribution around a bulk HTS magnet, however, is strongly non-uniform (conic profile predicted by the Bean model) compared to the rather flatter distribution around a ferromagnet. In the present work, we study how FeNi soft ferromagnetic alloys of different shapes can be combined with (RE)BCO bulk superconductors to improve the distribution of trapped field or its average value at the surface of the bulk sample. The FeNi ferromagnetic alloys are machined into pieces of various shapes (e.g. cylinder, cone) attached to the bottom surface of the bulk HTS disks. The magnetic properties of each ferromagnetic/superconductor (F/S) assembly are measured under axial magnetic field at 77 K. Small coils and Hall probe mappings provide the average magnetization and field distribution respectively. The results are compared to the intrinsic magnetic hysteresis curves of the magnetic alloys and of the superconductor. Measurements of the average magnetization show that the effects of the ferromagnetic alloys depend mainly on the volume of the ferromagnet and add up to the effect of the superconductor. However, at constant ferromagnetic volume, the shape of the ferromagnetic piece is found to influence the magnetic field penetration and distribution against the top surface of the superconductor. [less ▲]

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See detailMagnetic characterisation of large grain, bulk Y–Ba–Cu–O superconductor–soft ferromagnetic alloy hybrid structures
Philippe, Matthieu ULg; Fagnard, Jean-François ULg; Kirsch, Sébastien ULg et al

in Physica C: Superconductivity (2014), 502

Large grain, bulk Y–Ba–Cu–O (YBCO) high temperature superconductors (HTS) have significant potential for use in a variety of practical applications that incorporate powerful quasi-permanent magnets. In ... [more ▼]

Large grain, bulk Y–Ba–Cu–O (YBCO) high temperature superconductors (HTS) have significant potential for use in a variety of practical applications that incorporate powerful quasi-permanent magnets. In the present work, we investigate how the trapped field of such magnets can be improved by combining bulk YBCO with a soft FeNi, ferromagnetic alloy. This involves machining the alloy into components of various shapes, such as cylinders and rings, which are attached subsequently to the top surface of a solid, bulk HTS cylinder. The effect of these modifications on the magnetic hysteresis curve and trapped field of the bulk superconductor at 77 K are then studied using pick-up coil and Hall probe measurements. The experimental data are compared to finite element modelling of the magnetic flux distribution using Campbell’s algorithm. Initially we establish the validity of the technique involving pick-up coils wrapped around the bulk superconductor to obtain its magnetic hysteresis curve in a non-destructive way and highlight the difference between the measured signal and the true magnetization of the sample. We then consider the properties of hybrid ferromagnet/superconductor (F/S) structures. Hall probe measurements, together with the results of the model, establish that flux lines curve outwards through the ferromagnet, which acts, effectively, like a magnetic short circuit. Magnetic hysteresis curves show that the effects of the superconductor and the ferromagnet simply add when the ferromagnet is saturated fully by the applied field. The trapped field of the hybrid structure is always larger than that of the superconductor alone below this saturation level, and especially when the applied field is removed. The results of the study show further that the beneficial effects on the trapped field are enhanced when the ferromagnet covers the entire surface of the superconductor for different ferromagnetic components of various shapes and fixed volume. [less ▲]

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See detailMagnetic confinement of the superconducting condensate in superconductor-ferromagnet hybrid composites
Gillijns, W.; Aladyshkin, A Yu; Silhanek, Alejandro ULg et al

in Physical Review. B : Condensed Matter (2007), 76(6),

The influence of an inhomogeneous magnetic field on the magnetoresistance of thin Al films, used in different superconductor-ferromagnet hybrids, has been investigated. Two contrasting magnetic textures ... [more ▼]

The influence of an inhomogeneous magnetic field on the magnetoresistance of thin Al films, used in different superconductor-ferromagnet hybrids, has been investigated. Two contrasting magnetic textures with out-of-plane magnetization are explored: namely, (i) a plain film in a multidomain state and (ii) an array of microsized dots. The stray fields of the ferromagnetic structures confine the superconducting condensate and, accordingly, modify the condition for the nucleation of superconductivity. By switching between different magnetic states of the ferromagnet, this confinement can be tuned at will, thereby reversibly changing the dependence of the critical temperature T-c on an external magnetic field H. In particular, continuous evolution from a conventional linear T-c(H) dependence with a single maximum to a reentrant superconducting phase boundary with multiple T-c peaks has been demonstrated. [less ▲]

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See detailMagnetic diffusion-limited aggregation
Vandewalle, Nicolas ULg; Ausloos, Marcel ULg

in Physical Review. E : Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics (1995), 51(1), 597-603

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See detailMagnetic Eden model
Ausloos, Marcel ULg; Vandewalle, Nicolas ULg; Cloots, Rudi ULg

in Europhysics Letters [=EPL] (1993), 24(8), 629-634

We introduce the <<Magnetic Eden Model(s)>>. It consists in the usual Eden growth model(s), but allowing for the elements of the growth to have an extra degree of freedom (a <<spin>>). The growth is ... [more ▼]

We introduce the <<Magnetic Eden Model(s)>>. It consists in the usual Eden growth model(s), but allowing for the elements of the growth to have an extra degree of freedom (a <<spin>>). The growth is controlled by a condition depending on the <<magnetic state>> of the perimeter (through some <<spin coupling>>) and an external parameter, the <<magnetic field>>. Even though these words seem to refer to some <<energetic condition>> the growth model is of purely kinetic origin. This is demonstrated by exactly solving the 1-dimensional growth model for a semi-open chain, and, e.g. finding the correlation functions. In two-dimensions, simulations of clusters lead us to show that the perimeter growth exponent is coupling dependent. We show the morphologies of growth clusters on a <<phase diagram>> and indicate the <<physical origin>> and transition(s) between compact and lacunar clusters. [less ▲]

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See detailMagnetic fabrics in jotunite dykes from the Late-Proterozoic Rogaland anorthosite province (SW Norway)
Bolle, Olivier ULg; Besse, Michal; Diot, Hervé

in Geophysical Research Abstracts (2005), 7

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See detailMagnetic fabrics in the Holum granite (Vest-Agder, southernmost Norway): implications for the late evolution of the Sveconorwegian (Grenvillian) orogen of SW Scandinavia
Bolle, Olivier ULg; Diot, Hervé; Trindade, Ricardo I.F.

in Precambrian Research (2003), 121(3-4), 221-249

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See detailMagnetic field studies of massive main sequence stars
Schöller, M.; Hubrig, S.; Ilyin, I. et al

in American Institute of Physics Conference Series (2012, May 01)

We report on the status of our spectropolarimetric observations of massive stars. During the last years, we have discovered magnetic fields in many objects of the upper main sequence, including Be stars ... [more ▼]

We report on the status of our spectropolarimetric observations of massive stars. During the last years, we have discovered magnetic fields in many objects of the upper main sequence, including Be stars, β Cephei and Slowly Pulsating B stars, and a dozen O stars. Since the effects of those magnetic fields have been found to be substantial by recent models, we are looking into their impact on stellar rotation, pulsation, and stellar winds. Accurate studies of the age, environment, and kinematic characteristics of the magnetic stars are also promising to give us new insight into the origin of the magnetic fields. Furthermore, longer time series of magnetic field measurements allow us to observe the temporal variability of the magnetic field and to deduce the stellar rotation periods and the magnetic field geometry. Studies of the magnetic field in massive stars are indispensable to understand the conditions controlling the presence of those fields and their implications for the stellar physical parameters and evolution. [less ▲]

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See detailMagnetic field studies of massive main sequence stars
Schöller, M.; Hubrig, S.; Ilyin, I. et al

in Astronomische Nachrichten (2011), 332

We report on the status of our spectropolarimetric observations of massive stars. During the last years, we have discovered magnetic fields in many objects of the upper main sequence, including Be stars ... [more ▼]

We report on the status of our spectropolarimetric observations of massive stars. During the last years, we have discovered magnetic fields in many objects of the upper main sequence, including Be stars, β Cephei and Slowly Pulsating B stars, and a dozen O stars. Since the effects of those magnetic fields have been found to be substantial by recent models, we are looking into their impact on stellar rotation, pulsation, stellar winds, and chemical abundances. Accurate studies of the age, environment, and kinematic characteristics of the magnetic stars are also promising to give us new insight into the origin of the magnetic fields. Furthermore, longer time series of magnetic field measurements allow us to observe the temporal variability of the magnetic field and to deduce the stellar rotation period and the magnetic field geometry. Studies of the magnetic field in massive stars are indispensable to understand the conditions controlling the presence of those fields and their implications on the stellar physical parameters and evolution. [less ▲]

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See detailMagnetic fields in beta Cep, SPB, and Be stars
Schoeller, M.; Hubrig, S.; Briquet, Maryline ULg et al

in Proceedings of the Conference: "Putting A Stars into Context: Evolution, Environment, and Related Stars" (2013, September 01)

Recent observational and theoretical results emphasize the potential significance of magnetic fields for structure, evolution, and environment of massive stars. Depending on their spectral and photometric ... [more ▼]

Recent observational and theoretical results emphasize the potential significance of magnetic fields for structure, evolution, and environment of massive stars. Depending on their spectral and photometric behavior, the upper main-sequence B-type stars are assigned to different groups, such as beta Cep stars and slowly pulsating B (SPB) stars, He-rich and He-deficient Bp stars, Be stars, BpSi stars, HgMn stars, or normal B-type stars. All these groups are characterized by different magnetic field geometry and strength, from fields below the detection limit of a few Gauss up to tens of kG. Our collaboration was the first to systematically study the magnetic fields in representative samples of different types of main-sequence B stars. In this article, we give an overview about what we have learned during the last years about magnetic fields in beta Cep, SPB, and Be stars. [less ▲]

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See detailMagnetic fields in massive stars
Hubrig, S.; Scholler, M.; Briquet, Maryline ULg et al

in Contributions of the Astronomical Observatory Skalnaté Pleso (2008), 38

We review the recent discoveries of magnetic fields in different types of massive stars and briefly discuss strategies for spectropolarimetric observations to be carried out in the future.

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See detailMagnetic fields in O stars
Nazé, Yaël ULg

in Mathys, Gauthier; Griffin, E.; Kochukhov, O. (Eds.) et al Putting A Stars into Context: Evolution, Environment, and Related Stars (2014, November 01)

During the last decade, large-scale, organized (generally dipolar) magnetic fields with strengths between 0.1 and 20 kG have been detected in dozens of OB stars. This contribution reviews the impact of ... [more ▼]

During the last decade, large-scale, organized (generally dipolar) magnetic fields with strengths between 0.1 and 20 kG have been detected in dozens of OB stars. This contribution reviews the impact of such fields on the stellar winds of O-type stars, with emphasis on variability and X-ray emission. [less ▲]

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See detailMagnetic fields in O stars
Nazé, Yaël ULg

in proceedings of "Putting A-stars into context" (2013)

Over the last decade, large-scale, organized (generally dipolar) magnetic fields with a strength between 0.1 and 20 kG were detected in dozens of OB stars. This contribution reviews the impact of such ... [more ▼]

Over the last decade, large-scale, organized (generally dipolar) magnetic fields with a strength between 0.1 and 20 kG were detected in dozens of OB stars. This contribution reviews the impact of such magnetic fields on the stellar winds of O-stars, with emphasis on variability and X-ray emission. [less ▲]

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See detailMagnetic fields in O-, B- and A-type stars on the main sequence
Briquet, Maryline ULg

in CoRoT Symposium 3 / Kepler KASC-7 joint meeting (in press)

In this review, the latest observational results on magnetic fields in main-sequence stars with radiative envelopes are summarised together with the theoretical works aimed at explaining them.

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See detailMagnetic fields of HgMn stars
Hubrig, S.; González, J. F.; Ilyin, I. et al

in Astronomy and Astrophysics (2012), 547

Context. The frequent presence of weak magnetic fields on the surface of spotted late-B stars with HgMn peculiarity in binary systems has been controversial during the two last decades. Recent studies of ... [more ▼]

Context. The frequent presence of weak magnetic fields on the surface of spotted late-B stars with HgMn peculiarity in binary systems has been controversial during the two last decades. Recent studies of magnetic fields in these stars using the least-squares deconvolution (LSD) technique have failed to detect magnetic fields, indicating an upper limit on the longitudinal field between 8 and 15 G. In these LSD studies, assumptions were made that all spectral lines are identical in shape and can be described by a scaled mean profile. <BR /> Aims: We re-analyse the available spectropolarimetric material by applying the moment technique on spectral lines of inhomogeneously distributed elements separately. Furthermore, we present new determinations of the mean longitudinal magnetic field for the HgMn star HD 65949 and the hotter analog of HgMn stars, the PGa star HD 19400, using FORS 2 installed at the VLT. We also give new measurements of the eclipsing system AR Aur with a primary star of HgMn peculiarity, which were obtained with the SOFIN spectropolarimeter installed at the Nordic Optical Telescope. <BR /> Methods: We downloaded from the European Southern Observatory (ESO) archive the publically available HARPS spectra for eight HgMn stars and one normal and one superficially normal B-type star obtained in 2010. Out of this sample, three HgMn stars belong to spectroscopic double-lined systems. The application of the moment technique to the HARPS and SOFIN spectra allowed us to study the presence of the longitudinal magnetic field, the crossover effect, and quadratic magnetic fields. Results for the HgMn star HD 65949 and the PGa star HD 19400 are based on a linear regression analysis of low-resolution spectra obtained with FORS 2 in spectropolarimetric mode. <BR /> Results: Our measurements of the magnetic field with the moment technique using spectral lines of several elements separately reveal the presence of a weak longitudinal magnetic field, a quadratic magnetic field, and the crossover effect on the surface of several HgMn stars as well as normal and superficially normal B-type stars. Furthermore, our analysis suggests the existence of intriguing correlations between the strength of the magnetic field, abundance anomalies, and binary properties. The results are discussed in the context of possible mechanisms responsible for the development of the element patches and complex magnetic fields on the surface of late B-type stars. Based on observations obtained at the European Southern Observatory (ESO programmes 076.D-0169(A), 076.D-0172(A), 084.D-0338(A), 085.D-0296(A), 085.D-0296(B), 087.D-0049(A), 088.D-0284(A)), SOFIN observations at the 2.56 m Nordic Optical Telescope on La Palma, and observations obtained with the CORALIE Echelle Spectrograph on the 1.2 m Euler Swiss telescope on La Silla, Chile.Tables 2-7, 9, 10 are only available in electronic form at <A href="http://www.aanda.org">http://www.aanda.org</A> [less ▲]

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