LOCAL DESTRUCTION OF ANTIFERROMAGNETIC SPIN CORRELATION IN HIGH-TC SUPERCONDUCTOR (LA1-XSRX)2CU0.99M0.01O4-Z (M=GA,FE)

The origin of T(c)-suppression in the impurity-doped high-T(c) superconductor (La1-xSrx)2Cu0.99M0.01O4-z (M=Ga,Fe) is investigated through the measurements of resistivity, magnetization and ESR. By substitution of Ga or Fe for 1% of Cu atoms, T(c) is depressed and maximum T(c) is shifted to higher Sr-concentration by about 0.5% and 1.0%, respectively. This shift can be attributed to hole reduction by doped trivalent ions and to magnetic pair breaking of Fe spins. Apparent effective moment per Fe in Fe-doped samples increases from 4.0 to 5.5 mu(B) with increasing Sr-concentration. This indicates that localized spin density is induced around Fe ions and couples antiferromagnetically with Fe spins but the spin density reduces with increasing itinerant hole carriers. It is suggested that the appearance of static spin density around doped Ga or Fe destroys antiferromagnetically correlated spin system on the CuO2 plane, leading to T(c)-suppression.