AC SUSCEPTIBILITY STUDY OF YBCO SINTERED SAMPLES NEAR THE TRANSITION-TEMPERATURE

Y1Ba2Cu3O7-x sintered samples have been investigated near the transiti on temperature by means of AC susceptibility technique. In particular, the intragranular contribution to the imaginary part of susceptibilit y (chi '') has been studied as a function of the field frequency (f = 17 Hz + 1070 Hz) in a narrow temperature range (few degrees) around Tc (congruent to 92.0 K). Different frequency dependences of chi '' have been found as the temperature varies. For temperatures T < 91.9 K chi '' is found to increase linearly with In f, whereas for T greater tha n or equal to 98.9 K a linear frequency dependence is found. Moreover, for T < 92.3K the zero frequency limit approaches to a finite value, whereas for T > 92.3K such limit is zero.