Giant Oxygen Isotope Effect on the Spin Glass Transition inLa2−xSrxCu1−zMnzO4as Revealed by Muon Spin Rotation

Abstract

We have observed a huge oxygen isotope effect on the spin glass transition in ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{Cu}}_{1\ensuremath{-}z}{\mathrm{Mn}}_{z}{\mathrm{O}}_{4}$ ( $x\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.03$ and 0.05, $z\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.02$) using the muon-spin-rotation technique. Upon replacing ${}^{16}\mathrm{O}$ with ${}^{18}\mathrm{O}$, the spin glass freezing temperature ${T}_{g}$ in the Mn-doped samples increases by about $80%$ for $x\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.03$ and $30%$ for $x\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.05$. 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 taking into account the polaronic nature of charge carriers in cuprates.