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Title: Exchange bias mediated by interfacial nanoparticles (invited)

The objective of this study on the iconic exchange-bias bilayer Permalloy/CoO has been to identify those elements of the interfacial microstructure and accompanying magnetic properties that are responsible for the exchange-bias and hysteretic properties of this bilayer. Both epitaxial and polycrystalline samples were examined. X-ray and neutron reflectometry established that there existed an interfacial region, of width ∼1 nm, whose magnetic properties differed from those of Py or CoO. A model was developed for the interfacial microstructure that predicts all the relevant properties of this system; namely; the temperature and Permalloy thickness dependence of the exchange-bias, H{sub EX}, and coercivity, H{sub C}; the much smaller measured values of H{sub EX} from what was nominally expected; the different behavior of H{sub EX} and H{sub C} in epitaxial and polycrystalline bilayers. A surprising result is that the exchange-bias does not involve direct exchange-coupling between Permalloy and CoO, but rather is mediated by CoFe{sub 2}O{sub 4} nanoparticles in the interfacial region.
Authors:
 [1] ;  [2] ;  [1] ;  [3] ;  [4]
  1. Department of Physics, University of California, San Diego, La Jolla, California 92093 (United States)
  2. (United States)
  3. Center for Magnetic Recording Research, University of California, California 92093 (United States)
  4. Department of Physics, Arizona State University, Tempe, Arizona 85287 (United States)
Publication Date:
OSTI Identifier:
22402967
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 117; Journal Issue: 17; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; COBALT OXIDES; COERCIVE FORCE; COUPLING; EPITAXY; IRON OXIDES; LAYERS; MAGNETIC PROPERTIES; MICROSTRUCTURE; NANOPARTICLES; NEUTRON DIFFRACTION; PERMALLOY; POLYCRYSTALS; X-RAY DIFFRACTION