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Full-Text Articles in Physics
Possible Room-Temperature Ferromagnetism In Hydrogenated Carbon Nanotubes, Adam L. Friedman, Hyunkyung Chun, Yung Joon Jung, Don Heiman, Evan R. Glaser, Latika Menon
Possible Room-Temperature Ferromagnetism In Hydrogenated Carbon Nanotubes, Adam L. Friedman, Hyunkyung Chun, Yung Joon Jung, Don Heiman, Evan R. Glaser, Latika Menon
Donald Heiman
We find that ferromagnetism can be induced in carbon nanotubes (CNTs) by introducing hydrogen. Multiwalled CNTs grown inside porous alumina templates contain a large density of defects resulting in significant hydrogen uptake when annealed at high temperatures. This hydrogen incorporation produces H-complex and adatom magnetism which generates a sizable ferromagnetic moment and a Curie temperature near TC=1000 K. We studied the conditions for the incorporation of hydrogen, the temperature-dependent magnetic behavior, and the dependence of the ferromagnetism on the size of the nanotubes.
Negative Index Metamaterials Based On Metal-Dielectric Nanocomposites For Imaging Applications, L. Menon, W. T. Lu, A. L. Friedman, S. P. Bennett, D. Heiman, S. Sridhar
Negative Index Metamaterials Based On Metal-Dielectric Nanocomposites For Imaging Applications, L. Menon, W. T. Lu, A. L. Friedman, S. P. Bennett, D. Heiman, S. Sridhar
Donald Heiman
Negative index metamaterials are demonstrated based on metal-dielectric nanocomposites prepared using a versatile bottom-up nanofabrication approach. The method involves the incorporation of vertically aligned metal nanowires such as Au and Ag inside dielectric aluminum oxide nanotemplates. Optical absorbance measurements show resonance peaks corresponding to the transverse and longitudinal surface plasmon modes. A quantitative model based on effective medium theory is in excellent agreement with experimental data, and points to specific composite configurations and wavelength regimes where such structures can have applications as negative refraction media for imaging.
Ferromagnetism In Thin-Film Cr-Doped Topological Insulator Bi₂Se₃, P. P.J. Haazen, J. -B. Laloe, T. J. Nummy, H. J.M. Swagten, P. Jarillo-Herrero, D. Heiman, J. S. Moodera
Ferromagnetism In Thin-Film Cr-Doped Topological Insulator Bi₂Se₃, P. P.J. Haazen, J. -B. Laloe, T. J. Nummy, H. J.M. Swagten, P. Jarillo-Herrero, D. Heiman, J. S. Moodera
Donald Heiman
We report on the observation of ferromagnetism in epitaxial thin films of the topological insulator compound Bi2Se3 with chromium doping. The structural, magnetic, and magnetoelectrical properties of Bi2Se3 were investigated for Cr concentrations up to 10%. For a Cr content up to ∼5% the films are of good crystalline quality, with the lattice parameter a decreasing and the lattice parameter c increasing with increasing Cr concentration. The Curie temperature reached a maximum TC = 20 K for 5.2% Cr. Well-defined ferromagnetic hysteresis in the magnetization and in the magnetoresistance was also observed in these films.