Effect of Size in (Bi,Pb)2Sr2Ca2Cu3O10+y Superconducting Grains

E. Govea-Alcaide; L. Pérez-Acosta; P. Muné; R. F. Jardim

E. Govea-Alcaide Departamento de Física, Universidad de Oriente, Patricio Lumumba s/n, P. O. Box. 90500, Santiago de Cuba, Cuba
L. Pérez-Acosta Departamento de Física, Facultad de Mecánica, Universidad de Camagüey, Circunvalación Norte Km 5 1/2 s/n, Camaguey, Cuba
P. Muné Departamento de Física, Universidad de Oriente, Patricio Lumumba s/n, P. O. Box. 90500, Santiago de Cuba, Cuba
R. F. Jardim Instituto de Física, Universidade de São Paulo, CP 66318, 05315-970, S. Paulo, SP, Brazil

Abstract

We have present an experimental study on the magnetic properties of (Bi,Pb)₂Sr₂Ca₂Cu_10+y (Bi-2223) ceramic samples obtained by using the ball-milling method. After the last heat treatment, the resulting material, were ballmilled from 120 to 240 minutes. The compositions of the obtained samples are very similar as inferred from the X-ray diffraction pattern. It was found that all the indexed reflection is related to the Bi-2223 phase. We have also found an increase in the width of peaks, at half the maximum intensity, with increasing the milling time. By using the Scherrer formula we were able to estimate de mean size of grains in the samples yielding in the range between 31 to 17 nm. The analysis of the magnetic susceptibility as a function of temperature, χ(T), revealed appreciable qualitative and quantitative changes between experimental curves. For temperature below a certain temperature, T_eff, the experimental data show a paramagnetic behavior (χ ~ 1/T), which is interpreted by considering a parity effect associated with the number of electrons within the superconducting grains.