Electronic specific heat of La(2-x)Sr(x)Cu(1-y)M(y)O(4)(M=Ga, Zn): Impurity effects on a d-wave superconductor

The electronic specific heat C-el was studied in Ga- and Zn-doped La2-xSrxCuO4 (0.16 less than or equal to x less than or equal to 0.22) at T less than or equal to 10K. Partial substitution of Ga or Zn for Cu suppresses T-c and revives the T-linear electronic specific heat, gamma T, markedly. The gamma(y)/gamma(N) vs T-c/T-c0 relation for Zn-doped samples with x greater than or equal to 0.2 is in good agreement with the theoretical one for resonant impurity scattering in a d-wave superconductor, while those for Ga-doped samples and for Zn-doped samples with x < 0.2 deviate slightly from the theoretical curve. The deviation will be discussed in relation to changes in the magnetic properties of 3d electrons.