Tuning the electronic properties of the 4d transition metal oxide LaRhO₃

Perovskite transition metal oxides exhibit various novel properties due to strong correlations among their d electrons. These correlation effects are well known in the 3d transition metal oxides, such as LaCoO₃, where multiple spin states can be observed. Electronic correlations are expected to change as the transition metal is changed from a 3d element to a 4d element in the same column of the periodic table, for example changing from Co to Rh. To explore these changes, we grow epitaxial La_1-xSr_xRhO₃ thin films with Sr concentrations as large as 50% using molecular beam epitaxy. Hall measurements show a sign change from hole-like conduction for low doping to electron-like conduction for a large doping level of x=0.3. Systematic changes in electronic structure as a function of doping are predicted by theory and may provide a basis for understanding electronic correlations in transition metal oxides.