Bulk Single Crystal-Like Structural and Magnetic Characteristics of Epitaxial Spinel Ferrite Thin Films with Elimination of Antiphase Boundaries.

Abstract

Spinel ferrite NiFe₂ O₄ thin films have been grown on three isostructural substrates, MgAl₂ O₄ , MgGa₂ O₄ , and CoGa₂ O₄ using pulsed laser deposition. These substrates have lattice mismatches of 3.1%, 0.8%, and 0.2%, respectively, with NiFe₂ O₄ . As expected, the films grown on MgAl₂ O₄ substrate show the presence of the antiphase boundary defects. However, no antiphase boundaries (APBs) are observed for films grown on near-lattice-matched substrates MgGa₂ O₄ and CoGa₂ O₄ . This demonstrates that by using isostructural and lattice-matched substrates, the formation of APBs can be avoided in NiFe₂ O₄ thin films. Consequently, static and dynamic magnetic properties comparable with the bulk can be realized. Initial results indicate similar improvements in film quality and magnetic properties due to the elimination of APBs in other members of the spinel ferrite family, such as Fe₃ O₄ and CoFe₂ O₄ , which have similar crystallographic structure and lattice constants as NiFe₂ O₄ .