Magnetic order and electronic phase diagrams of electron-doped copper oxide materials

We report muon spin relaxation and rotation measurements on sintered ceramic samples of ${\mathrm{Nd}}_{2\mathrm{-}\mathit{x}}$ ${\mathrm{Ce}}_{\mathit{x}}$ ${\mathrm{CuO}}_{4\mathrm{-}\mathit{y}}$ and a large single crystal of ${\mathrm{Nd}}_2$ ${\mathrm{CuO}}_{4\mathrm{-}\mathit{y}}$. We find an electronic phase diagram that is quite similar to that of hole-doped superconductors such as ${\mathrm{La}}_{2\mathrm{-}\mathit{x}}$ ${\mathrm{Sr}}_{\mathit{x}}$ ${\mathrm{CuO}}_{4\mathrm{-}\mathit{y}}$, although the doping of electrons into the system is less efficient in destroying the static moments on the copper ions. Static magnetic order appears in ${\mathrm{Nd}}_2$ ${\mathrm{CuO}}_{4\mathrm{-}\mathit{y}}$ below about 250 K; two spin reorientations are seen at T=75 and 35 K, providing information about the muon site in this material.