Atomic Structure and Electron Magnetic Circular Dichroism of Individual Rock Salt Structure Antiphase Boundaries in Spinel Ferrites

• Published in: Advanced functional materials Vol. 31; no. 21
• Main Authors: Li, Zhuo, Lu, Jinlian, Jin, Lei, Rusz, Ján, Kocevski, Vancho, Yanagihara, Hideto, Kita, Eiji, Mayer, Joachim, Dunin‐Borkowski, Rafal E., Xiang, Hongjun, Zhong, Xiaoyan
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc 01.05.2021
• Subjects: Antiferromagnetism; Antiphase boundaries; antiphase boundary; atomic defect structure; Atomic structure; Coupling; Crystal structure; Density functional theory; Dichroism; Electron energy; electron magnetic circular dichroism; First principles; first principles calculations; Imaging techniques; Industrial applications; Interlayers; Magnetic moments; Magnetic properties; Magnetoresistance; Magnetoresistivity; Materials science; Nickel ferrites; Scanning transmission electron microscopy; Spatial resolution; Spinel; spinel ferrites; transmission electron microscopy
• ISSN: 1616-301X; 1616-3028; 1616-3028
• DOI: 10.1002/adfm.202008306

Spinel ferrites are an important class of materials, whose magnetic properties are of interest for industrial applications. The antiphase boundaries (APBs) that are commonly observed in spinel ferrite films can hinder their applications in spintronic devices and sensors, as a result of their influence on magnetic degradation and magnetoresistance of the materials. However, it is challenging to correlate magnetic properties with atomic structure in individual APBs due to the limited spatial resolution of most magnetic imaging techniques. Here, aberration‐corrected scanning transmission electron microscopy and electron energy‐loss magnetic chiral dichroism are used to measure the atomic structure and electron magnetic circular dichroism (EMCD) of a single APB in NiFe2O4 that takes the form of a rock salt structure interlayer and is associated with a crystal translation of (1/4)a[011]. First principles density functional theory calculations are used to confirm that this specific APB introduces antiferromagnetic coupling and a significant decrease in the magnitude of the magnetic moments, which is consistent with an observed decrease in EMCD signal at the APB. The results provide new insight into the physical origins of magnetic coupling at an individual defect on the atomic scale. The atomic structure and electron magnetic circular dichroism (EMCD) spectra of an antiphase boundary (APB) containing a rock salt structure interlayer in a spinel ferrite is investigated in the transmission electron microscope. Magnetic degradation at the APB interlayer is measured experimentally and its physical origin is assessed by combining EMCD, density functional theory, and dynamical diffraction calculations.