2 research outputs found
Texture effect on vortex-state TF-”+SR in Bi-2223 high-Tc materials
International audienceThe influence of texture in Biâ2223 ingots on the temperature dependence of the ÎŒ+ spin relaxation rate has been investigated. Texture was induced during coldâisostaticâpressing by applying an additional uniaxial load which tends to align single grain c axes along the stress direction, ĆŸ. Small plates were cut with faces either â or â„ ĆŸ and ÎŒSR was measured in a 15 mT transverse field (TF) during cooling from room temperature to 6 K. While for highlyâtextured material, lowâtemperature limits are substantially smaller than expected, the large shift (55%) observed when switching from ĆŸâ„TF to ĆŸâTF clearly indicates that anisotropy has developed. Relaxation rates for the weaklyâtextured sample lie in between. To a lesser extent, sintering also enhanced the lowâtemperature relaxation, but did not affect TC significantly. All samples showed a weak onset of depolarization between 60 K and 90 K, most likely due to the presence of a Biâ2212 impurity phase. This impurity phase might cause the transitionâtemperature smearing in the 100â110 K range in the weakly textured (and less compacted) material. Thus the sharpness of the relaxation drop might be relevant for assessment of material quality and be used as a criterion in the improvement of the production process