Giant oxygen isotope effect on the spin glass transition in La2-xSrxCu1-zMnzO4 as revealed by muon spin rotation

We have observed a huge oxygen isotope effect on the spin glass transition in La2-xSrxCu1-zMnzO4 (x = 0.03 and 0.05, z = 0.02) using the muon-spin-rot ation technique. Upon replacing O-16 with O-18, the spin glass freezing tem perature T-g in the Mn-doped samples increases by about 80% fur x = 0.03 an d 30% for x = 0.05. On the other hand, T-g has a small isotope shift in the Mn-free samples. These novel isotope effects clearly demonstrate a strong effect of electron-phonon interaction on magnetism which can be explained t aking into account the polaronic nature of charge carriers in cuprates.