Role of anti-phase boundaries in the formation of magnetic domains in magnetite thin films

Abstract

Anti-phase boundaries (APBs) are structural defects which have been shown to be responsible for the anomalous magnetic behavior observed in different nanostructures. Understanding their properties is crucial in order to use them to tune the properties of magnetic materials by growing APBs in a controlled way since their density strongly depends on the synthesis method. In this work we investigate their influence on magnetite (Fe 3 O 4 )thinfilmsby considering an atomistic spin model, focussing our study on the role that the exchange interactions play across the APB interface. We conclude that the main atypical features reported experimentally in this material are well described by the model we propose here, confirming the new exchange interactions created in the APB as the responsible for this deviation from bulk properties.

Signature of antiphase boundaries in iron oxide nanoparticles

“…The most notable feature of APB-I is the breaking of the long B-site chains perpendicular to the boundary plane, which results in a modification of the bond angle between iron atoms in these chains from 90 to 180 and a subsequent change of the magnetic superexchange interaction from ferromagnetic to antiferromagnetic. As noted before, this has an impact on the magnetic properties of iron oxide nanoparticles (Nedelkoski et al, 2017) and thin films (Moreno et al, 2021). The resulting antiferromagnetic superexchange between octahedral Fe 3+ ions across the boundary has been confirmed…”

Tunable Control of the Structural Features and Related Physical Properties of MnxFe3–xO4 Nanoparticles: Implication on Their Heating Performance by Magnetic Hyperthermia

“…The relative shift of the ferrite cation sublattices across the boundary alters the exchange magnetic interactions, which become predominantly antiferromagnetic of the kinds A−A and B−B. 57,82 As a consequence, it appears as an exchange coupling in the region nearby an APB that increases H C and H K due to the resulting spin canting layer. 59,83,84 In this sense, the absence of saturation in NF and the higher values of H C and H K with respect to S2 are consistent with a higher density of APBs for NF and support the more notable decrease of the coherent crystallite size relative to the TEM mean particle diameter already encountered in the XRD analysis.…”