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Exchange bias in a nanogranular system with competing ferromagnetic and antiferromagnetic exchange interactions
Author(s) -
Hu Yong,
Du An
Publication year - 2011
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.201046430
Subject(s) - condensed matter physics , antiferromagnetism , ferromagnetism , coercivity , exchange bias , spins , materials science , exchange interaction , magnetization , coupling (piping) , ising model , magnetic field , physics , magnetic anisotropy , quantum mechanics , metallurgy
A nanogranular system with inverted ferromagnetic (FM)–antiferromagnetic (AFM) core–matrix morphology is investigated by conducting a modified Monte Carlo Metropolis method. Effects of the AFM‐ and FM‐component ratios on exchange bias field ( H E ) and coercivity ( H C ) are presented at low temperature after field cooling, respectively. The sign of H E is negative for weak cooling fields ( H FC ) but positive for strong ones. The value of H E increases monotonically with the increasing radius of the AFM core ( R AF ) at the expense of the FM matrix for weak and strong H FC , while it is non‐monotonic when H FC is equal to a critical value, which just overcomes the AFM interfacial coupling energy. With the pure increase of the FM dimension, the value of H E decreases firstly and finally levels off at low temperature after cooling in weak or strong H FC . However, H E is around zero and shifts slightly to a positive value for the same critical H FC . The behaviors of H C are independent of H FC . A monotonic decrease of H C with increasing R AF and the opposite trend with increasing FM dimension are both detected in the present system. The phenomena have been interpreted well by analyzing the magnetization reversal and energy competition mechanisms. The increase of R AF stabilizes the magnetic spin configuration of the AFM nanoparticles to contribute to H E , while large numbers of the FM spins may weaken the AFM pinning effect, resulting in the suppression of H E .