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Title: Exchange bias effect in Au-Fe3O4 dumbbell nanoparticles induced by the charge transfer from gold

We have studied the origin of the exchange bias effect in the Au-Fe3O4 dumbbell nanoparticles in two samples with different sizes of the Au seed nanoparticles (4.1 and 2.7 nm) and same size of Fe3O4 nanoparticles (9.8 nm). The magnetization, small-angle neutron-scattering, synchrotron x-ray diffraction, and scanning transmission electron microscope measurements determined the antiferromagnetic FeO wustite phase within Fe3O4 nanoparticles, originating at the interface with the Au nanoparticles. The interface between antiferromagnetic FeO and ferrimagnetic Fe3O4 is giving rise to the exchange bias effect. The strength of the exchange bias fields depends on the interfacial area and lattice mismatch between both phases. We propose that the charge transfer from the Au nanoparticles is responsible for a partial reduction of the Fe3O4 into the FeO phase at the interface with Au nanoparticles. The Au-O bonds are formed, presumably across the interface to accommodate an excess of oxygen released during the reduction of magnetite
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Publication Date:
OSTI Identifier:
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. B, Condensed Matter and Materials Physics; Journal Volume: 92; Journal Issue: 5
American Physical Society (APS)
Research Org:
Argonne National Laboratory (ANL)
Sponsoring Org:
USDOE Office of Science - Office of Basic Energy Sciences - Materials Sciences and Engineering Division; USDOE Office of Science - Office of Biological and Environmental Research; USDOE Office of Science - Office of Basic Energy Sciences - Scientific User Facilities Division
Country of Publication:
United States