Spin canting across core/shell Fe3O4/MnxFe3–xO4 nanoparticles
- Carnegie Mellon Univ., Pittsburgh, PA (United States); National Inst. of Standards and Technology (NIST), Boulder, CO (United States)
- Carnegie Mellon Univ., Pittsburgh, PA (United States)
- Sci-Tech Daresbury Campus, Daresbury (United Kingdom); Univ. of York, York (United Kingdom); The York-JEOL Nanocentre, York (United Kingdom)
- Univ. of York, York (United Kingdom)
- Univ. of Manitoba, Winnipeg (Canada)
- Oberlin College, Oberlin, OH (United States)
- National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States)
Magnetic nanoparticles (MNPs) have become increasingly important in biomedical applications like magnetic imaging and hyperthermia based cancer treatment. Understanding their magnetic spin configurations is important for optimizing these applications. The measured magnetization of MNPs can be significantly lower than bulk counterparts, often due to canted spins. This has previously been presumed to be a surface effect, where reduced exchange allows spins closest to the nanoparticle surface to deviate locally from collinear structures. We demonstrate that intraparticle effects can induce spin canting throughout a MNP via the Dzyaloshinskii-Moriya interaction (DMI). We study ~7.4 nm diameter, core/shell Fe3O4/MnxFe3–xO4 MNPs with a 0.5 nm Mn-ferrite shell. Mössbauer spectroscopy, x-ray absorption spectroscopy and x-ray magnetic circular dichroism are used to determine chemical structure of core and shell. Polarized small angle neutron scattering shows parallel and perpendicular magnetic correlations, suggesting multiparticle coherent spin canting in an applied field. Atomistic simulations reveal the underlying mechanism of the observed spin canting. These show that strong DMI can lead to magnetic frustration within the shell and cause canting of the net particle moment. Furthermore these results illuminate how core/shell nanoparticle systems can be engineered for spin canting across the whole of the particle, rather than solely at the surface.
- Research Organization:
- Carnegie Mellon Univ., Pittsburgh, PA (United States); UChicago Argonne, LLC, Lemont, IL (United States)
- Sponsoring Organization:
- USDOE
- Grant/Contract Number:
- FG02-08ER46481; AC02-06CH11357
- OSTI ID:
- 1500105
- Journal Information:
- Scientific Reports, Vol. 8, Issue 1; ISSN 2045-2322
- Publisher:
- Nature Publishing GroupCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
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