Antiferromagnet thickness dependence and rotatable spins in exchange biased CoO/Fe films

•Investigation on emergence of exchange bias and coercivity enhancement in epitaxial CoO/Fe films with ultrathin CoO, even before the frozen CoO spins are detectable.•Observation of different CoO thickness dependence of the exchange bias and coercivity enhancement, including the evolution of magneti...

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Veröffentlicht in:Journal of magnetism and magnetic materials 2022-12, Vol.563 (C), p.169898, Article 169898
Hauptverfasser: Greene, Peter K., Hu, Yong, Qiu, Ziqiang, Liu, Kai
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Sprache:eng
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Zusammenfassung:•Investigation on emergence of exchange bias and coercivity enhancement in epitaxial CoO/Fe films with ultrathin CoO, even before the frozen CoO spins are detectable.•Observation of different CoO thickness dependence of the exchange bias and coercivity enhancement, including the evolution of magnetization reversal from being influenced by rotatable to frozen CoO moments.•The AF domain state is found to be metastable, which can be reoriented by external and exchange fields prior to the appearance of frozen spins, pointing to a generic origin of the training effect.•Monte Carlo simulations show that the AF anisotropy energy barrier and the rotatable spins induced by magnetic field and exchange interaction at the interface are responsible for the observed effects. The emergence of exchange bias and coercivity enhancement has been investigated in epitaxial CoO/Fe films with varied antiferromagnet (AF) thicknesses, even smaller than the critical value where the frozen CoO spins are detectable. Vector magnetometry and first-order reversal curve (FORC) measurements reveal different CoO thickness dependence of the exchange bias and coercivity enhancement, including the evolution of magnetization reversal from a high coercivity, low bias phase due to rotatable CoO moments to a high bias, low coercivity phase due to frozen CoO moments. The AF domain state is found to be metastable, which can be reoriented by external and exchange fields prior to the appearance of frozen spins, pointing to a generic origin of the training effect. Monte Carlo simulations show that the AF anisotropy energy barrier and the rotatable spins induced by magnetic field and exchange interaction at the interface are responsible for the observed effects.
ISSN:0304-8853
DOI:10.1016/j.jmmm.2022.169898