Abstract
The interplay of lattice, charge, orbital, and spin degrees of freedom in complex oxides covers a broad spectrum of intriguing functionalities and offers tremendous opportunities for next-generation electronic devices. Over the past decade, advanced synthesis techniques assisted with in situ characterizations have been applied to demonstrate complex oxide thin films and various combinations of heterostructures, suggesting new possibilities to create and design devices with tantalizing functionalities. Among them, one type of heterostructures drawing a considerable spotlight is high interface-to-volume ratio vertical nanostructures. Vertical nanostructures can be used to impose heteroepitaxial strain on a material to tune the properties thereof. Examples can be found in the (La,Ca)MnO3-MgO system with tunable Curie temperatures or the BaTiO3-CoFe2O4 (CFO) system with enhanced interfacial coupling. Interfacial couplings in self-assembled nanostructures, especially in complex oxide composites, have been considered as a powerful tool to create and manipulate the lattice, charge, orbital, and spin degrees of freedoms. New functionalities have been unveiled by the choice of a proper combination of constituents. However, while most of the studies to date have stressed the functional controllability of heterostructures using external electric or magnetic fields, rarely has the attention been placed on exploring other external control parameters. Motivated by this, in order to introduce light (or photons) as an external control parameter in a self-assembled nanostructure system, we chose a large photostrictive SrRuO3 (SRO) as the matrix material to couple with the large magnetostrictive CFO nanopillars. In this system, SRO is a well-known “bad metal” oxide material, of which the resistivity shows a kink at its Curie temperature. Unlike the perovskite manganites with colossal magnetoresistance (CMR) effect, SRO does not show an impressive magnetoresistance (MR). Therefore, our motivation is to create a model system to see how the magnetic nanostructures directly affect the macroscopic transport behavior of the metallic matrix. The findings here are very attractive since it demonstrates that an unanticipated low-field magnetoresistance (LFMR) effect (~40% at 0.5T) at around TC,SRO can be achieved in this non-manganites-based system. This implies the mechanism behind LFMR may be a more common phenomenon. This work delivers a solution to trigger new functionalities in the strongly correlated systems and therefore opens a new pathway to engineer and design the functionalities of hetero-epitaxial oxide nanostructures.

CV-eddie.pdf