Manifestation of higher-order inter-granular exchange in magnetic recording media

Exchange coupling between magnetic grains is essential for maintaining the stability of stored information in magnetic recording media. Using an atomistic spin model, we have investigated the coupling between neighbouring magnetic grains where magnetic impurity atoms have migrated into the non-magne...

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Bibliographic Details
Published in:Applied physics letters 2017-08, Vol.111 (8)
Main Authors: Ellis, Matthew O. A., Ababei, Razvan-V., Wood, Roger, Evans, Richard F. L., Chantrell, Roy W.
Format: Article
Language:English
Subjects:
Applied physics
Computer simulation
Coupling
Decay rate
Exchanging
Grain boundaries
Impurities
Magnetic recording
Magnetic storage
Magnetic tape
Recording instruments
Temperature dependence
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Summary:Exchange coupling between magnetic grains is essential for maintaining the stability of stored information in magnetic recording media. Using an atomistic spin model, we have investigated the coupling between neighbouring magnetic grains where magnetic impurity atoms have migrated into the non-magnetic grain boundary. We find that when the impurity density is low, a biquadratic term in addition to the bilinear term is found to better describe the inter-granular exchange coupling. The temperature dependence of both terms is found to follow a power law behaviour with the biquadratic exchange constant decaying faster than the bilinear. For the increasing grain boundary thickness, the inter-granular exchange reduces and also decays more quickly with temperature. Further simulations of a grain at a bit boundary show an unexpected energy minimum for in-plane magnetisation. This feature is reproduced if the biquadratic exchange term is included.
ISSN:0003-6951
1077-3118
DOI:10.1063/1.4990604