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

Journal Article · Mon Jul 21 00:00:00 EDT 2014 · Applied Physics Letters

DOI:https://doi.org/10.1063/1.4890580· OSTI ID:22311146

Cortie, D. L. ^[1]; Biternas, A. G.; Chantrell, R. W. ^[2]; Wang, X. L. ^[1]; Klose, F. ^[3]

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1. The Institute for Superconducting and Electronic Materials, The University of Wollongong, Wollongong, NSW 2522 (Australia)
2. Department of Physics, University of York, YO10 5DD (United Kingdom)
3. Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234 (Australia)

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.

• OSTI ID: 22311146
• Journal Information: Applied Physics Letters, Vol. 105, Issue 3; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0003-6951
• Country of Publication: United States
• Language: English

Related Subjects

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