3D tailoring of all-oxide heterostructures by ion beams

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Inter-relations among charge, spin, orbital and lattice parameters are largely demonstrated in multi-functional oxide materials which exhibit a variety of exotic properties, ranging from superconductivity, insulator-metal transition, colossal magnetoresistance, charge ordering, and orbital ordering, etc. In particular, tilting a delicate energy balance in lattice interactions and kinetics, achieved by temperature, pressure or chemical control, may result in exotic phenomena in these systems. However, fine-tailoring such interactions has proven difficult. In this context, defect engineering by ion irradiation, which can introduce strain and electronic disorder, has emerged as a powerful technique to fine tune inaccessible complex phases of oxide thin films. In this proposal, we aim at the modulation of the magnetic, electrical and ferroic properties of NiCo2O4 and its heterostructure with BiFeO3 by ion irradiation. By employing lithography and/or focused ion beam, 3D defect engineering therefore tailoring physical properties of NiCo2O4/BiFeO3 can be realized. The final goal is to exam such a tuned heterostructure as a venue of novel spintronics devices. The National Chiao Tung University group is well versed in the fabrication of the epitaxial NiCo2O4 and BiFeO3 thin films. The group at HZDR has the possibility of irradiating these films with ions of different specimen and energies on demand. The detailed structural, magnetic and electric characterization will be performed using the techniques at HZDR. The group at TU Chemnitz will use spin-polarized electronic structure calculations with density functional theory (DFT) in understanding the changes. Therefore, the combination of scientists from these groups can establish a new pathway of 3D tailoring of oxide heterostructures useful for designing new functionalities.