1,392,809 research outputs found
The magnetization behaviour of lightly doped YBa2Cu3O6+x
No full textThe static magnetic susceptibility of two different YBa2Cu3O6.30 samples shows a peak near to 45 K; the peak shows a dependence on the field and on the magnetic history. This feature has been explained by the combined effect of regions with a Curie-like behavior and superconducting regions. The origin of these regions in the material has been discussed
Low-temperature magnetic behavior of perovskite compounds PbFe1/2Ta1/2O3 and PbFe1/2Nb1/2O3
No full textThe isostructural perovskite compounds PbFe(1/2)Ta(1/2)O3 and PbFe(1/2)Nb(1/2)O3 have been known for long time, and they are part of the important class of materials called multiferroic, where ferroelasticity, ferroelectricity, and ferromagnetism coexist. In the literature regarding PbFe(1/2)Ta(1/2)O3 and PbFe(1/2)Nb(1/2)O3, an "anomaly" of their low-temperature magnetic behavior has not always been reported. Moreover, both the origin of this behavior, and the cause for which it was not always observed, were never completely explained. In this paper, the magnetic behavior of the two compounds at low temperature has been extensively studied and explained as the occurring of a spin-glasslike transition
Investigation of a peaked feature in the magnetic susceptibility of YBa2Cu3O6.30 samples
No full textThe static magnetic susceptibility of two different YBa2Cu3O6.30 samples has been measured at different fields in the range 2 – 300 K, using a superconducting quantum interference device magnetometer; one sample has been prepared by oxygen intercalation, the other one by deintercalation.
The susceptibility shows a peak near 45 K in both samples, which depends on the field and the magnetic history. The susceptibility of semiconducting and superconducting compounds, with an oxygen content O6.20 and O6.41, respectively, has also been investigated. The presence of the peak in the YBa2Cu3O6.30 samples has been explained by the combined effect of regions with a Curie-like behaviour and superconducting regions. The origin of these regions is discussed
Lehmann Acoumeter
No full textUsed to test auditory acuity, the Lehmann acoumeter can emit tones with varying frequency and intensity (pitch and volume) (Whipple, 1914)
Annealing and quenching effect on superconductivity and magnetic propreties of YBa2Cu3O7-d
No full textElectronic structure of PbFe1/2Ta1/2O3: Crystallographic ordering and magnetic properties
No full textWe report electronic structure calculations for the multiferroic ferromagnetoelectric perovskite PbFe1/2Ta1/2O3, within density functional theory in the local spin density approximation (LSDA) and within the LSD+U approach. Our results, corresponding to several possible crystallographic and magnetic orderings, show the link between short range cation coordination and magnetic properties. In particular, the existence of two different Néel ordering temperatures, experimentally evidenced, is explained in terms of different superexchange paths introduced by crystallographic orderings certainly present, locally, in the real samples. The introduction of ferroelectric displacements, which are found to be in good agreement with experiment, do not bring about large changes in the electronic structure of this system
Rietveld refinements of the paraelectric and ferroelectric structures of PbFe0.5Ta0.5O3
No full textThe high symmetry parent phase and the two derived low symmetry phases of the complex perovskite PbFe0.5Ta0.5O3 have been refined by the Rietveld method from neutron powder diffraction data. The analysed powders were obtained by grinding single crystals. Owing to the Very small distortions from the cubic structure, the lattice symmetry of the derived phases was determined by means of synchrotron radiation powder diffraction. At 350 K the cubic phase (which is known to be stable for T > 270 K) is characterized by positional disorder or anharmonic thermal motion of lead atoms, as happens in most Pb-based complex perovskites. It was refined in space group Pm (3) over bar m, with strongly anisotropic thermal motion of oxygen atoms. The synchrotron powder diffraction pattern of the intermediate phase (stable for 220 K < T < 270 K), collected at 230 K, agrees with a small tetragonal distortion. Neutron data at 230 K were refined in symmetry P4mm. Only oxygen atoms are significantly displaced from the cubic positions. The analysis of line broadening and splitting in the synchrotron radiation patterns collected at 130 K and 15 K indicate the low temperature symmetry to be monoclinic. Neutron data at 15 K were refined in space group Cm
- …
