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Title: Tunability of exchange bias in Ni@NiO core-shell nanoparticles obtained by sequential layer deposition

Films of magnetic Ni@NiO core–shell nanoparticles (NPs, core diameter d ≅ 12 nm, nominal shell thickness variable between 0 and 6.5 nm) obtained with sequential layer deposition were investigated, to gain insight into the relationships between shell thickness/morphology, core-shell interface, and magnetic properties. Different values of NiO shell thickness ts could be obtained while keeping the Ni core size fixed, at variance with conventional oxidation procedures where the oxide shell is grown at the expense of the core. Chemical composition, morphology of the as-produced samples and structural features of the Ni/NiO interface were investigated with x-ray photoelectron spectroscopy and microscopy (scanning electron microscopy, transmission electron microscopy) techniques, and related with results from magnetic measurements obtained with a superconducting quantum interference device. The effect of the shell thickness on the magnetic properties could be studied. The exchange bias (EB) field Hbias is small and almost constant for ts up to 1.6 nm; then it rapidly grows, with no sign of saturation. This behavior is clearly related to the morphology of the top NiO layer, and is mostly due to the thickness dependence of the NiO anisotropy constant. The ability to tune the EB effect by varying the thickness of the lastmore » NiO layer represents a step towards the rational design and synthesis of core–shell NPs with desired magnetic properties.« less
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [5] ;  [5]
  1. National Research Council (CNR-NANO), Rome (Italy)
  2. National Research Council (CNR-IMEM), Parma (Italy). Imem Inst.
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  4. University of Tennessee, Knoxville (UTK)
  5. Lab. of Nanotechnology, Milano (Italy)
Publication Date:
OSTI Identifier:
1234318
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Nanotechnology (Print)
Additional Journal Information:
Journal Name: Nanotechnology (Print); Journal Volume: 26; Journal Issue: 40; Journal ID: ISSN 0957-4484
Research Org:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY