Atomic-Scale Structural Properties in NiCo[sub.2]O[sub.4]/CuFe[sub.2]O[sub.4] Bilayer Heterostructures on -MgAl[sub.2]O[sub.4] Substrate Regulated by Film Thickness

Changing film thickness to manipulate microstructural properties has been considered as a potential method in practical application. Here, we report that atomic-scale structural properties are regulated by film thickness in an NiC[sub.O2]O[sub.4](NCO)/CuFe[sub.2]O[sub.4](CFO) bilayer heterostructure prepared on (001)-MgAl[sub.2]O[sub.4] (MAO) substrate by means of aberration-corrected scanning transmission electron microscopy (STEM). The misfit dislocations at the NCO/CFO interface and antiphase boundaries (APBs) bound to dislocations within the films are both found in NCO (40 nm)/CFO (40 nm)/MAO heterostructures, contributing to the relaxation of mismatch lattice strain. In addition, the non-overlapping a/4[101]-APB is found and the structural transformation of this kind of APB is resolved at the atomic scale. In contrast, only the interfacial dislocations form at the interface without the formation of APBs within the films in NCO (10 nm)/CFO (40 nm)/MAO heterostructures. Our results provide evidence that the formation of microstructural defects can be regulated by changing film thickness to tune the magnetic properties of epitaxial bilayer spinel oxide films.