Magnetic Ordering in Gallate / Ferrite Hybrid Spinel Nanoparticles -- a New Platform for Functional Control of Magnetic, Optical, and Catalytic Properties

Heretofore, all-spinel magnetic nanoparticles (NPs) have focused almost exclusively on ferrites (AFe2O4), where A is typically another transition metal. We are developing a new class of all-spinel core shell NPs where the core material is a spinel gallate (AGa2O4). Use of gallate cores will enable new methods of control over NP properties, chiefly by exploiting the optical luminescence of gallates and by controlling the strain that the gallate core imparts onto the ferrite shell. The common spinel structure will promote epitaxial growth of the ferrite onto the gallate core. We will start our studies with ZnGa2O4 (ZGO) as the core and Fe3O4 (magnetite or FO) as the shell material. ZGO has a close lattice match with magnetite, which will help establish good epitaxy between the core and shell. Also, magnetite is bio-compatible and exhibits the well-known Verwey transition at ~120 K, which is characterized by an abrupt decrease in the magnetization of the magnetite. Temperature and magnetic field dependent SANS studies of ZGO / FO NPs will help establish the degree of magnetic ordering in the NPs and the coherence of structural / magnetic correlations across NPs.