Superconductivity and magnetism in the phase diagram of bulk La2-xCexCuO4+-delta investigated by muon-spin spectroscopy and neutron scattering

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Electron doped cuprates are mostly identified with the compounds Nd2-xCexCuO4+-( orPr2-xCexCuO4+-(. The simple reason is that these compounds can be synthesized bymany techniques from thin film methods to single crystal growth. In contrast, the electrondoped cuprate LA2-xCexCuO4+-( is not thermodynamically stable. So far, only thin filmsof La2-xCexCuO4+-( have been available. However, in order to analyze the magnetic andsuperconducting phase diagram in detail, bulk investigation methods as neutron scatteringand muon-spin relaxation and rotation free from thin film effects are indispensable. This iseven more important as the oxygen concentration at the different oxygen sites within thecrystal structure of La2-xCexCuO4+-( is only determinable by neutron scattering. Basedon our recent success to stabilize phase pure bulk La2-xCexCuO4+-( in the unstable T-structureby a low-temperature synthesis method, the phase diagram of La2-xCexCuO4+-( has nowbecome experimentally accessible. For the first time, it has become possible to synthesizebulk La 2-xCexCuO 4+-( , to determine the superconducting and transport properties, whileat the same time for all samples the oxygen site occupation, and the (co)existence ofsuperconducting and magnetic phases can be studied. As a result of this project, anauthoritative phase diagram of La2-x CexCuO 4+-( will be established, as is now availableonly for hole doped compounds such as La 2-xSrxCuO 4+-(.