We observe an enormous spontaneous exchange bias (∼300-600 Oe) - measured in an unmagnetized state following zero-field cooling - in a nanocomposite of BiFeO3 (∼94%)-Bi2Fe4O 9 (∼6%) over a temperature range 5-300 K. Depending on the path followed in tracing the hysteresis loop - positive (p) or negative (n) - as well as the maximum field applied, the exchange bias (HE) varies significantly with -HEp>HEn. The temperature dependence of HE is nonmonotonic. It increases, initially, till ∼150 K and then decreases as the blocking temperature TB is approached. All these rich features appear to be originating from the spontaneous symmetry breaking and consequent onset of unidirectional anisotropy driven by "superinteraction bias coupling" between the ferromagnetic core of Bi2Fe4O9 (of average size ∼19 nm) and the canted antiferromagnetic structure of BiFeO3 (of average size ∼112 nm) via superspin glass moments at the shell. © 2013 American Physical Society.
CITATION STYLE
Maity, T., Goswami, S., Bhattacharya, D., & Roy, S. (2013). Superspin glass mediated giant spontaneous exchange bias in a nanocomposite of BiFeO3-Bi2Fe4O9. Physical Review Letters, 110(10). https://doi.org/10.1103/PhysRevLett.110.107201
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