INVESTIGATION OF IMPURITY EFFECTS IN LA(2-X)SR(X)CU(1-Y)M(Y)O(4) (M=GA,ZN) BY ELECTRONIC SPECIFIC-HEAT

The electronic specific heat C-cl was studied at T less than or equal to 10K on Ga- and Zn-doped La2-xSrxCuO4 (0.16 less than or equal to x less than or equal to 0.22). In pure La2-xSrxCuO4 (0.16 less than or e qual to x less than or equal to 0.22), the C-cl at T much less than T- c contains only a T-2 component but no T-linear one, which is peculiar to a clean d-wave superconductor. Partial substitution of Ga or Zn fo r Cu changes the T-2-term of C-cl into a quite different one described by the sum of a T-linear and a nearly T-3 term. The coefficient of th e T-linear term, gamma, markedly increases with Zn- or Ga-content. The gamma/gamma(N) vs. T-C/T-C0, relation for Zn-doped samples with x gre ater than or equal to 0.2 is in good agreement with the theoretical cu rve for resonant impurity scattering in a d-wave superconductor, while those for Ga-doped samples and for Zn-doped samples with x<0.2 deviat e slightly from the theoretical curve. Such a deviation will be discus sed in relation to the change in the magnetic properties of the presen t system caused by impurity-doping.