SUPERCONDUCTING ANISOTROPY IN THE Y-BASED SYSTEM SUBSTITUTED FOR THE Y, BA AND CU SITES

Temperature and angular dependencies of the resistivity in magnetic fi elds have been measured on the c-axis oriented thin films prepared by magnetron sputtering, in order to investigate superconducting anisotro py in the Y-based system in which the Y, Pa and Cu sites were substitu ted by the Pr, Nd, and Co and Zn ions, respectively. In the Y1-xPrxBa2 Cu3Oy and YBa2(Cu1-xCox)(3)O-y systems the anisotropic parameter gamma , which is represented by the ratio of the coherence length xi(ab) to xi(c), increases from 5.5 to 10 and 19 with increase of the Pr and Co content, respectively. In the YBa2(Cu1-xZnx)(3)O-y system gamma decrea ses from 5.5 to 1.6 with increasing Zn ions. The parameter gamma shows anomalous behaviour in the Nd1+xBa2-xCu3Oy system, in that it first i ncreases and later decreases in a higher Nd concentration region. Thes e phenomena have been discussed in terms of the effects by the substit ution to the superconducting CuO2 plane and CuO chain such as a change of the carrier number and a randomness or a distortion on the CuO2 pl ane. It has been concluded that there is as a general tendency for the superconducting anisotropy to increase when the substituted ions affe ct the CuO chains, and to decrease in the case of the introduction of randomness or distortion to the CuO2 planes. (C) 1997 Elsevier Science B.V.