Speaker: Matthias Hepting, MPI-FKF Stuttgart
Time: April 5, 2016, 1:30 - 2:30
The rich phase diagram of transition metal oxides (TMO) such as rare-earth nickelates RNiO3 (R = rare-earth) results from the interplay between charge, orbital, spin, and lattice degrees of freedom. In the talk it will be described how this interplay can be manipulated in epitaxial RNiO3 heterostructures and how new phases can be designed, distinct from the ones existing in bulk materials. We have used polarized Raman scattering in conjunction with resonant soft X-ray diffraction to probe modified electronic and magnetic phases in superlattices (SLs) of PrNiO3 with the wide-gap insulator PrAlO3. In ultrathin (001) oriented SLs under compressive strain a metallic state with fully developed spin order but without presence of charge order was found. This novel ground state corresponds to a pure spin-density wave phase which was predicted by theory. In similar SLs composed of NdNiO3 and NdGaO3 but oriented in the pseudocubic (111) direction certain properties of the Ni spin spiral, like magnetic moment sizes and collinearity, turn out to be tunable by the nickelate layer thickness. The findings demonstrate that tailored TMO heterostructures can help to achieve control over the collective phase behavior of correlated-electron systems.