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Title: Microscopic model for exchange bias from grain-boundary disorder in a ferromagnet/antiferromagnet thin film with a nanocrystalline microstructure

Monte Carlo spin simulations were coupled to a Voronoi microstructure-generator to predict the magnitude and behavior of exchange bias in a ferromagnet/antiferromagnet (AF) thin film bilayer with a nanocrystalline microstructure. Our model accounts for the effects of irregular grain-shapes, finite-sized particles, and the possible presence of local random-fields originating from the antiferromagnet's grain-boundary regions. As the grain-boundary represents a crystal-structure distortion, we model the local effect on the exchange constants in the Gaussian approximation which can cause regions resembling a spin glass confined to an unusual 2D topology. Although an ensemble of completely disconnected AF grains isolated by non-magnetic barriers provides a small exchange bias, the introduction of a spin-glass network at the boundaries causes a four-fold enhancement in the magnitude of the loop-shift. This implies the importance of local grain-boundary behavior in defect-engineered antiferromagnets.
Authors:
 [1] ;  [2] ;  [3] ; ;  [4] ;  [1] ;  [5] ;  [6]
  1. The Institute for Superconducting and Electronic Materials, The University of Wollongong, Wollongong, NSW 2522 (Australia)
  2. (Australia)
  3. (Canada)
  4. Department of Physics, University of York, YO10 5DD (United Kingdom)
  5. Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234 (Australia)
  6. (China)
Publication Date:
OSTI Identifier:
22311146
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 105; Journal Issue: 3; Other Information: (c) 2014 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; ANTIFERROMAGNETIC MATERIALS; APPROXIMATIONS; CRYSTAL DEFECTS; CRYSTAL STRUCTURE; CRYSTALS; FERROMAGNETIC MATERIALS; GRAIN BOUNDARIES; LAYERS; MONTE CARLO METHOD; NANOMATERIALS; NANOSTRUCTURES; RANDOMNESS; SIMULATION; SPIN; SPIN GLASS STATE; THIN FILMS; TOPOLOGY