Browsing by Author "Wolff, M"

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    Chemical-order-induced magnetic exchange bias in epitaxial FePt3 films
    (American Physical Society, 2008-04-11) Lott, D; Klose, F; Ambaye, H; Mankey, GJ; Mani, P; Wolff, M; Schreyer, A; Christen, HM; Sales, BC
    We show that magnetic exchange bias can be induced by means of chemical ordering. The effect was observed on epitaxial thin film layers of FePt3, a material which has the remarkable property that, depending on the degree of chemical order, a ferromagnetic and an antiferromagnetic magnetic state can coexist at the same temperature. We demonstrate that the observed exchange bias originates at the interfaces between these two different magnetic phases of FePt3. © 2008, American Physical Society
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    Structural and magnetic properties of epitaxial Fe25Pt75
    (American Vacuum Society, 2009-07) Lu, Z; Walock, MJ; LeClair, PR; Mankey, GJ; Mani, P; Lott, D; Klose, F; Ambaye, H; Lauter, V; Wolff, M; Schreyer, A; Christen, HM; Sales, BC
    Epitaxial films of Fe25Pt75 have a number of different magnetic phases as a function of temperature and chemical order. For example, chemically ordered epitaxial films have two distinct antiferromagnetic phases at temperatures below similar to 160 K and exhibit paramagnetism above that temperature. In sharp contrast, chemically disordered epitaxial films are ferromagnetic with a Curie temperature that is greater than 400 K. It is demonstrated that by varying the substrate temperature during growth, epitaxial films with varying degrees of chemical order can be produced and it is possible to produce an alloy with the same composition throughout the film with a modified magnetic structure. The authors used polarized neutron reflectivity to gauge the magnetism of a Fe25Pt75 sample produced with a periodic variation in the growth temperature and showed that the sample exhibits a reduced Curie temperature of approximately 300 K as compared to bulk Fe25Pt75. © 2009, American Vacuum Society