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Browsing by Author "Lee, H."

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    Direct Evidence of Anomalous Interfacial Magnetization in Metamagnetic Pd doped FeRh Thin Films
    (Nature Portfolio, 2015-03-16) Bennett, S. P.; Ambaye, H.; Lee, H.; LeClair, P.; Mankey, G. J.; Lauter, V.; United States Department of Energy (DOE); Oak Ridge National Laboratory; University of Alabama Tuscaloosa
    Palladium doped iron rhodium is a magnetic material of significant interest for it's close to room temperature magnetostructural phase transition from antiferromagnetic (AF) to ferromagnetic (FM) ordering. Here we report on the peculiarities of the magnetization distribution in thin films of FeRh(Pd) probed by Polarized Neutron Reflectometry. Remarkably, we've found thin interfacial regions with strong magnetization that have unique thermomagnetic properties as compared to the rest of the system. These regions exist at the top and bottom interfaces of the films while the central regions behave similarly to the bulk with a clear AF-FM order transition. Further we explore the impact of an additional Pt interlayer introduced in the middle of the FeRh(Pd) film and reveal that it serves to replicate the strong interfacial magnetization found at the top and bottom interfaces. These results are of great value both in understanding the fundamental physics of such an order transition, and in considering FeRh(Pd) for magnetic media and spintronics applications.
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    Magnetization Relaxation and Structure of CoFeGe Alloys
    (2009) Lee, H.; Wang, Y.-H. A.; Mewes, C. K. A.; Butler, W. H.; Mewes, T.; Maat, S.; York, B.; Carey, M. J.; Childress, J. R.; University of Alabama Tuscaloosa
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    Tailoring exchange bias through chemical order in epitaxial FePt3 films
    (American Institute of Physics, 2013-07-01) Saerbeck, T.; Zhu, H.; Lott, D.; Lee, H.; LeClair, P. R.; Mankey, G. J.; Stampfl, A. P. J.; Klose, F.; Australian Nuclear Science & Technology Organisation; University of Western Australia; Helmholtz Association; Helmholtz-Zentrum Geesthacht - Zentrum fur Material- und Kustenforschung; University of Alabama Tuscaloosa; University of Sydney
    Intentional introduction of chemical disorder into mono-stoichiometric epitaxial FePt3 films allows to create a ferro-/antiferromagnetic two-phase system, which shows a pronounced and controllable exchange bias effect. In contrast to conventional exchange bias systems, granular magnetic interfaces are created within the same crystallographic structure by local variation of chemical order. The amount of the exchange bias can be controlled by the relative amount and size of ferromagnetic and antiferromagnetic volume fractions and the interface between them. The tailoring of the magnetic composition alone, without affecting the chemical and structural compositions, opens the way to study granular magnetic exchange bias concepts separated from structural artifacts. (C) 2013 AIP Publishing LLC.