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ABSTRACT: A large-scale FePt nanocube monolayer was fabricated on silicon substrate by a simple spin-coating method. After sputtering a B4C thin film on the particle monolayer, these films were annealed at elevated temperature. Transmission electron microscope and magnetic property characterizations demonstrate that FePt nanocubes are well separated under high-temperature annealing and yield the magnetically attractive L10 phase without any indication of sintering under the protection of a B4 C layer. Moreover, it is observed that the texture of the nanocube monolayer is lost in the high-temperature annealing. The magnetic properties with Hc=2200 Oe along the film normal and Hc=1700 Oe along the film plane are obtained for the Fe46 Pt54 /B4 C thin film.
Physica Scripta 05/2010; 2010(T139):014071. · 1.20 Impact Factor
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ABSTRACT: We report on the ferromagnetic characteristics of Zn(1-x)Mn(x)O nanorods synthesized by a seed-mediated solution method. The as-doped ZnO nanorods had a length about 200 nm and a diameter ranging from 20 to 30 nm. Magnetic property measurements revealed that the Zn(1-x)Mn(x)O nanorods exhibited weak ferromagnetism at 305 K. Similar solution method were also employed to fabricate the (Mn, Cu) co-doped nanostructures. The presence of Cu2+ was found to change the nanorod morphology (in the case of pure ZnO) to nanoparticle. On the other hand, not only the hysteresis curve saturated at lower magnetic field, but also the saturation magnetization was increased with the Cu doping. Transmission electron microscopy, X-ray photoelectron spectroscopy and Photoluminescence analysis suggested that the room temperature (RT) ferromagnetism could be originated from the Mn2+ doped into the ZnO lattice, and additional carriers due to the Cu co-doping may enhance the room temperature ferromagnetism in the Mn:ZnO system.
Journal of Nanoscience and Nanotechnology 06/2009; 9(5):3308-12. · 1.56 Impact Factor
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ABSTRACT: We report on the ferromagnetic characteristics of Zn1−xMnxO nanorods synthesized by a seed-mediated solution method. The as-doped ZnO nanorods had a length about 200 nm and a diameter ranging from 20 to 30 nm. Magnetic property measurements revealed that the Zn1−xMnxO nanorods exhibited weak ferromagnetism at 305 K. Similar solution method were also employed to fabricate the (Mn, Cu) co-doped nanostructures. The presence of Cu2+ was found to change the nanorod morphology (in the case of pure ZnO) to nanoparticle. On the other hand, not only the hysteresis curve saturated at lower magnetic field, but also the saturation magnetization was increased with the Cu doping. Transmission electron microscopy, X-ray photoelectron spectroscopy and Photoluminescence analysis suggested that the room temperature (RT) ferromagnetism could be originated from the Mn2+ doped into the ZnO lattice, and additional carriers due to the Cu co-doping may enhance the room temperature ferromagnetism in the Mn:ZnO system.
Journal of Nanoscience and Nanotechnology 04/2009; 9(5):3308-3312. · 1.56 Impact Factor
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ABSTRACT: FePt/B4C multilayer composite films have been prepared by magnetron sputtering and subsequent annealing in vacuum. It was found that the B4C layers effectively serve as spacers to separate the FePt layers, enhancing (001) orientation of FePt alloy. Our results show that highly (001) oriented [Fe45Pt55(8 nm)/B4C (4 nm)]3 film with satisfactory perpendicular coercivity (4.75 kOe) has significant potential as a perpendicular recording medium.
Journal of Applied Physics 11/2007; 102(10):106101-106101-3. · 2.17 Impact Factor
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ABSTRACT: FePt/B4C multilayer thin films were deposited using magnetron sputtering with different boron carbide layer thicknesses. Experimental results suggest that the B4C layers effectively serve as spacers to separate the FePt layers, making the multilayer configuration stable even after film annealing at elevated temperatures. On the other hand, B and C are found to incorporate into the FePt layer, which is responsible for the FePt grain growth confinement and grain separation, and eventually affects the magnetic properties of the composite film.
Applied Physics Letters 08/2007; 91(6):061920-061920-3. · 3.84 Impact Factor
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ABSTRACT: Ni-doped ZnO nanocrystals have been synthesized by a wet chemical reaction. The nanocrystals have been investigated carefully by high resolution transmission electron microscopy and all the particles are found to be the known wurtzite ZnO. X-ray photoelectron spectroscopy and Raman spectra results provide the evidence that Ni <sup>2+</sup> is incorporated into the ZnO lattice at Zn <sup>2+</sup> site. Magnetic property measurements reveal that the as-grown Zn <sub>1-x</sub> Ni <sub>x</sub> O nanocrystals exhibit room temperature ferromagnetic behaviors with saturation magnetization of 0.01 emu / g and Curie temperature above 340 K for Ni concentration of ∼1% in atomic ratio.
Applied Physics Letters 02/2007; · 3.84 Impact Factor
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ABSTRACT: Interfacial reactions and electrical properties of HfO2 and HfAlO high-k gate dielectric films on strained Si1−xGex (x = 17%) fabricated by pulsed-laser deposition were investigated. The dielectric films were characterized by x-ray photoelectron spectroscopy, transmission electron microscopy, and electrical measurements. We found that alloying of HfO2 with alumina can reduce the GeOx formation at the interfacial layer and thus reduce the Ge diffusion during the film post-thermal annealing process. Such suppression effect significantly improved the electrical properties of the dielectric films.
Applied Physics Letters 05/2006; 88(18):182905-182905-3. · 3.84 Impact Factor
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ABSTRACT: Mn-doped ZnO nanorods with ∼30 nm in diameter and ∼200 nm in length were synthesized by a seed-mediated solution method. The structures, magnetic properties, as well as the annealing effect were characterized by transmission electron microscopy, electron energy loss spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectrum and physical properties measurement system. Magnetic properties measurement revealed that the Zn0.97Mn0.03O nanorods exhibited ferromagnetism with a saturation magnetization of 0.005 emu g−1 and a coercivity of 110 Oe at 305 K. After annealing the samples at 900 °C for 2 h in air, the nanorods were transformed into nanoparticle aggregates. The coercivity and saturation magnetization increased obviously. Detailed analyses proved that a phase-separation process was happened at the high temperature. In this process, most of the particles preserved the wurtzite ZnO structure, while a few small ones evolved into spinel-structured particles. The increasing of the ferromagnetism of the annealed sample is attributed to the formation of secondary phase ZnxMn3−xO4.
Materials Chemistry and Physics 113:884-888. · 2.23 Impact Factor
