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Investigations of magnetic thin films and high- Tc superconductivity

Thesis/Dissertation ·
OSTI ID:5332967
Magnetic behavior of low dimensional systems was investigated through the study of two kind of materials: (1) Fe/Ag single-crystal thin films; (2) Fe doped high {Tc} superconductors. Samples of Fe(110)/Ag(111) thin films were fabricated by molecular beam epitaxy. By studying the spin-wave excitations at the interfaces of Fe/Ag/Fe sandwiches, the existence of magnetic interaction between the two Fe films across the Ag layer was proved. The relation between the spin-wave excitations and the coupling strength of the two ferromagnets was calculated by a Green's function method. An island structure in quasi-two-dimensional thin films and its influence to the magnetic properties were also studied. In the study of Fe-doped high-{Tc} superconductors of YBa{sub 2}(Cu{sup 1{minus}x}Fe{sub x}){sub 3}O{sub 7{minus}{delta}} with 0 {le} x {le} 0.15, the superconducting critical temperature {Tc} was found to be suppressed by the Fe doping and drops to zero at x {approx} 0.17. An orthorhombic-to-tetragonal structural transition occurs at x {approx} 0.03. The Fe dopants were found to occupy primarily at the Cu(1) sites ({approximately}90%) and the Fe-Fe interactions can establish a magnetic ordering at T = 4.2K for x > 0.03, which coexists with the superconductivity.
Research Organization:
Johns Hopkins Univ., Baltimore, MD (United States)
OSTI ID:
5332967
Country of Publication:
United States
Language:
English