Exchange bias in a nanocrystalline hematite/permalloy thin film investigated with polarized neutron reflectometry

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dc.contributor.authorCortie, DLen_AU
dc.contributor.authorLin, KWen_AU
dc.contributor.authorShueh, Cen_AU
dc.contributor.authorHsu, HFen_AU
dc.contributor.authorWang, XLen_AU
dc.contributor.authorJames, Men_AU
dc.contributor.authorFritzsche, Hen_AU
dc.contributor.authorBrück, Sen_AU
dc.contributor.authorKlose, Fen_AU
dc.date.accessioned2014-05-05T03:32:59Zen_AU
dc.date.available2014-05-05T03:32:59Zen_AU
dc.date.issued2012-08-07en_AU
dc.date.statistics2014-05-05en_AU
dc.description.abstractWe investigated a hematite alpha-Fe2O3/permalloy Ni80Fe20 bilayer film where the antiferromagnetic layer consisted of small hematite grains in the 2 to 16 nm range. A pronounced exchange bias effect occurred below the blocking temperature of 40 K. The magnitude of exchange bias was enhanced relative to reports for identical compounds in large grain, epitaxial films. However, the blocking temperature was dramatically reduced. As the Neel temperature of bulk alpha-Fe2O3 is known to be very high (860 K), we attribute the low-temperature onset of exchange bias to the well-known finite-size effect which suppresses the Morin transition for nanostructured hematite. Polarized neutron reflectometry was used to place an upper limit on the concentration and length scale of a layer of uncompensated moments at the antiferromagnetic interface. The data were found to be consistent with an induced magnetic region at the antiferromagnetic interface of 0.5-1.0 mu(B) per Fe atom within a depth of 1-2 nm. The field dependence of the neutron spin-flip signal and spin asymmetry was analyzed in the biased state, and the first and second magnetic reversal were found to occur by asymmetric mechanisms. For the fully trained permalloy loop, reversal occurred symmetrically at both coercive fields by an in-plane spin rotation of ferromagnetic domains. © 2012, American Physical Society.en_AU
dc.identifier.articlenumber55408en_AU
dc.identifier.citationCortie, D. L., Lin, K. W., Shueh, C., Hsu, H. F., Wang, X. L., James, M., Fritzsche, H., Brück, S., & Klose, F. (2012). Exchange bias in a nanocrystalline hematite/permalloy thin film investigated with polarized neutron reflectometry. Physical Review B, 86(5), Article Number 054408. doi:10.1103/PhysRevB.86.054408en_AU
dc.identifier.govdoc4621en_AU
dc.identifier.issn1098-0121en_AU
dc.identifier.issue5en_AU
dc.identifier.journaltitlePhysical Review Ben_AU
dc.identifier.urihttp://dx.doi.org/10.1103/PhysRevB.86.054408en_AU
dc.identifier.urihttp://apo.ansto.gov.au/dspace/handle/10238/5537en_AU
dc.identifier.volume86en_AU
dc.language.isoenen_AU
dc.publisherAmerican Physical Societyen_AU
dc.subjectAsymmetryen_AU
dc.subjectMagnetizationen_AU
dc.subjectMagnetic field reversalen_AU
dc.subjectSpinen_AU
dc.subjectHematiteen_AU
dc.subjectScatteringen_AU
dc.titleExchange bias in a nanocrystalline hematite/permalloy thin film investigated with polarized neutron reflectometryen_AU
dc.typeJournal Articleen_AU
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