Speaker
Description
Hole doped transition metal oxides have been extensively investigated due to their many active degrees of freedom such as charge, spin, and orbital ordering. An interesting alternative to metal substitution in nickelates, e.g., RE2-xSrxNiO4, is achieved by oxygen doping, yielding RE2NiO4+d. The extra oxygen atoms have been evidenced to be mobile down to ambient temperature, adding an extra complexity to the electronic ordering scenario by sub-mesoscopic oxygen ordering. Further on, the large-scale oxygen ordering can be easily switched with T and/or O-doping, adapting different 3D modulation vectors, all indicating well-defined lock-in phases. What is particularly challenging here is that phases with different modulation vectors, but invariant O-stoichiometry, can be obtained at RT, depending on their thermal history. It makes these phases to become a new playground to explore the evolution of charge and spin ordering schemes at constant O-stoichiometry. In this context, using polarized neutron scattering on IN12@ILL we could unambiguously evidence the key role interstitial oxygen atoms have for magnetic ordering and exchange paths in e.g. Pr2NiO4.23, where the c-axis of the magnetic structure is directly scaled with the modulation vector of the O-ordering. We’ll discuss the potential of these unexpected structure/property relations at constant stoichiometry for the tuning of electronic ordering phenomena for different oxides, explored with neutron and synchrotron scattering.
