INFLUENCE OF RARE-EARTH IONIC RADIUS ON THE PROPERTIES OF NI- AND FE-SUBSTITUTED RBA(2)(CU(1-X)M(X))(3)O-7-GAMMA SYSTEMS (R=Y,ND,EU,GD,HO,TM M=NI,FE)

摘要

The crystal structure parameters, temperature dependences of resistance R(T), and concentration dependences of superconducting transition temperature T-c(x) for the Ni- and Fe-substituted RBa(2)Cu(1-x)M(x))3O(7-y) systems based on Y and several rare earths (R=Y,Nd,Eu,Gd,Ho,Tm; M=Ni,Fe) have been investigated. It was found that the partial derivative T-c/partial derivative x parameter for both kinds of substitution depends mainly on the value of R(3+) ionic radius of the host matrix. As R changes from Tm to Nd the value of partial derivative T-c/partial derivative x increases by approximately three and four times for Ni and Fe substitutions correspondingly. No correlations of the partial derivative T-c/partial derivative x value with R(3+) localized magnetic moment were observed. The prime role of R(3+) ionic radius variation on the properties of RBa(2)(Cu(1-x)M(x))3O(7-y) systems as well as the same effect observed earlier for R(1-x)Pr(x)Ba(2)Cu(3)O(7-y) systems are discussed. The essentially different shapes of superconducting transitions for the Ni- and Fe-substituted systems are pointed out. [References: 36]