Atomic-scale structure and formation of antiphase boundaries in α-Li_0.5Fe_2.5O₄ thin films on MgAl₂O₄(001) substrates

The occurrence of antiferromagnetic coupling at antiphase domain boundaries (APBs) of ferromagnetic materials holds potential applications for room-temperature spintronic devices. Here, we report formation mechanism and atomic-scale structure properties of APBs in α-Li_0.5Fe_2.5O₄ thin films on MgAl₂O₄ (001) substrates investigated by means of aberration-corrected scanning transmission electron microscopy. The APBs in the α-Li_0.5Fe_2.5O₄ films are either conservative or non-conservative. Across the APBs the oxygen sublattice in α-Li_0.5Fe_2.5O₄ is maintained, while the stacking sequence of the cation sublattice is interrupted. The propagation of APBs is found to occur in a complex way within the ferromagnetic films, including the dissociation of APBs and the formation of kinks. Importantly, the density of APBs can be tuned by controlling the thickness of the α-Li_0.5Fe_2.5O₄ films since the APBs bound interfacial dislocations contributing to film-substrate strain relaxation. Our results evidence that the nano-scale APBs in the α-Li_0.5Fe_2.5O₄ films are controllable and stable, which could be promising candidates for applications in nano-spintronic devices.