Nano-Structures & Nano-Objects最新文献

Multiferroic bismuth ferrite shows a massive interest in its potential application in magnetic and electronic devices however maintaining high purity in bismuth ferrite nanoparticles at different temperatures is a difficult task for researchers. Several samples are prepared with different annealing temperatures and investigated in different atmospheres to recognize magnetic and electrical properties. A xerogel powder of bismuth ferrite is synthesized by the sol-gel route. The powder then anneals at 500, 600, 700, and 800 °C to form a nanostructure. X-ray diffraction analysis confirms that the annealed samples are in rhombohedral structure with R3c space symmetry and show a significant increase in crystal size and reduction in lattice strain with increasing annealing temperature. FESEM reveals the microstructural features of annealed nanoparticles which represent the conversion of spherical to cubic morphology with annealing temperature. Vibrating sample magnetometer investigations were conducted as a function of annealing and surface (300, 200, 80 K) temperatures. Insignificant variations of saturation magnetization are detected with surface temperature, but considerable degradation is observed with increasing annealing temperatures. The band-gap energy of bismuth ferrite nanoparticles annealed at 500, 600, 700, and 800 ºC is measured and significant escalation is observed from 1.93 to 2.06 eV. Electrical property analyses have been investigated as a function of frequency at different surface temperatures of 50, 100, 150, 200, 250, 300, and 350 °C. Remarkable variations are established in the electric and magnetic properties. Bismuth ferrite has been widely investigated due to its promising multifunctional device applications such as memory devices, spintronics, sensors, actuators, and photocatalytic and photovoltaic applications.

In this work, we investigated the tailoring of structural and magnetic properties of NiCu nanowires through electrodeposition. Continuous (S1) and composition-modulated (S2) wires were fabricated by electrodeposition using porous alumina membranes as a template. Morphological characterization revealed that the total length of the wires was 8 ± 3 µm in both S1 and S2. For the composition-modulated wires, the length of the segments with the lowest and highest Cu concentrations was 1.2 ± 0.4 µm and 226 ± 65 nm, respectively. Mapping by energy dispersive spectroscopy (EDS) revealed that the concentration of copper and nickel varied along the length of the composition-modulated nanowires, while the continuous nanowires contained a relatively constant concentration of both metals. It is demonstrated that the change in Cu concentration along the wire modifies the lattice parameter, average crystallite size (D) and lattice strain (ε) of Ni. This result is pivotal for understanding the magnetic properties of the wires, as nickel is primarily responsible for the magnetic behavior of the wires. From the ferromagnetic resonance (FMR) results, the linewidth and resonance field values for samples S1 and S2 were determined. It was demonstrated that the greater deformation in the nickel lattice in NiCu nanowires increases the angular dependence of the resonance field. Furthermore, the smaller nickel crystallite size was shown to increase spin dispersion and magnetic damping, leading to complex behavior in FMR responses. Finally, it was demonstrated how Cu can influence the magnetic properties such as coercivity (H_C) and squareness (M_R/M_S) of the wires. Overall, this work contributes to understanding the tailoring of structural and magnetic properties of NiCu nanowires through electrodeposition.

Single-domain configuration is one of the important key in the applied current- technology especially information technology. In order to address this issue, a magnetic modification of cobalt ferrite nanoparticles (CFO-NPs) by decorating the monazite-natural-mineral (Ce) is presented. Monazite-decorated CFO-NPs are successfully synthesized by the co-precipitation method. The obtained nanoparticle samples are annealed at 200 °C, 300 °C, and 400 °C for 5 hours. XRD results confirms the successful decoration of the monazite sand with CFO-NPs, as demonstrated by the distinctive peaks of CFO-NPs, as well as the major peaks of the monazite-sand. The presence of monazite in the CFO-NPs sample was confirmed by the EDS results. With increasing annealing temperature, the crystallite size increases, respectively. FTIR results show that the monazite-decorated CFO-NPs outcome absorption peaks at k_t ∼590/cm and k_o ∼390/cm, which are the original absorptions of CFO-NPs. VSM results showed that the single-domain configuration realized owing high the H_C (supported by K₁ and K_σ) for samples without and annealed at 200 °C, whereas the multi-domain configuration appears to have a small H_C (supported only by K₁) for samples annealed at 300 °C and 400 °C. The largest H_C of the monazite-decorated CFO-NPs was obtained with the annealing temperature at 200 °C, i.e., 3.02 kOe, suggesting that it be supported by both the K₁ and K_σ. The magnetic properties obtained also indicate the potential for developing permanent magnets.