LA-139 NQR RELAXATION AND MU-SR STUDY OF LA2CU1-XZNXO4

La-139 NQR spectra, mu SR precessional frequencies and NQR relaxation rates W driven by the Cu2+ spin fluctuations are used to study the sta tic magnetic properties and the low-energy spin excitations upon subst itution of Zn2+ (S=0) for Cu2+ (S=1/2) in the antiferromagnetic (AF) p hases of La2Cu1-xZnxO4. It is found that the Neel temperatures T-N dec rease with IL almost linearly, with initial suppression rate close to 4, while the sublattice magnetization is only slightly affected, close to the behaviour expected for a 2D S=1/2 Heisenberg AF in the framewo rk of dilution model. Also the spin wave spectrum appears slightly aff ected by Zn doping, with moderate effects possibly related to disorder in the AF interactions and/or to finite size. A novel and remarkable effect is observed for T less than or equal to 100 K. The relaxation r ates W show large maxima, with x-dependent W-max and T-max. This pheno menon is attributed to the cooperative freezing of local magnetic mome nts induced by Zn on Cu orbitals. Information on the characteristic fl uctuation frequencies and on the spin-glass state superimposed to the AF matrix are thus obtained.