Cobalt

About: Cobalt is a research topic. Over the lifetime, 69899 publications have been published within this topic receiving 1242058 citations. The topic is also known as: Co & Element 27.

Effect of reducing atmosphere on the magnetism of Zn1?xCoxO (0?x?0.10) nanoparticles

Abstract: We report the crystal structure and magnetic properties of Zn1−xCoxO (0≤x≤010) nanoparticles synthesized by heating metal acetates in organic solvent The nanoparticles were crystallized in the wurtzite ZnO structure after annealing in air and in a forming gas (Ar95% + H5%) The x-ray diffraction and x-ray photoemission spectroscopy (XPS) data for different Co content show clear evidence for the Co2+ ions in tetrahedral symmetry, indicating the substitution of Co2+ in the ZnO lattice However, samples with x = 008 and higher cobalt content also indicate the presence of Co metal clusters Only those samples annealed in the reducing atmosphere of the forming gas, that showed the presence of oxygen vacancies, exhibited ferromagnetism at room temperature The air annealed samples remained non-magnetic down to 77 K The essential ingredient in achieving room temperature ferromagnetism in these Zn1−xCoxO nanoparticles was found to be the presence of additional carriers generated by the presence of the oxygen vacancies

Synthesis of Metal and Metal Oxide Nanowire and Nanotube Arrays within a Mesoporous Silica Template

Abstract: Metallic nanowires of cobalt, copper, and iron oxide magnetite (Fe3O4) have been synthesized within the pores of mesoporous silica using a supercritical fluid inclusion technique. The mesoporous matrix provides a means of producing a high density of stable, hexagonally ordered arrays of highly crystalline nanowires. The formation of the metal and metal oxide nanowires within the silica mesopores was confirmed by transmission electron microscopy (TEM), N2 adsorption experiments, and powder X-ray diffraction (PXRD). The mechanism of nanowire formation within the mesopores appears to occur through the initial binding and coating of the pore walls with the metal atoms to form tubelike structures within the mesoporous template. The thickness of these tubes subsequently increases with further metal deposition until nanowires are formed. Additionally, the crystal structure of the cobalt nanowires formed within the mesoporous template can be readily changed by manipulating the density of the supercritical fluid p...

Spectral-structural correlations in high-spin cobalt(II) complexes

Abstract: The spectral and magnetic properties of simple high spin cobalt(II) complexes are reviewed with the aim of showing how it is possible to relate the experimental data to the electronic structure and the coordination geometry of the complexes. It is hoped that this may be of help to all researchers who need to characterize cobalt(II) complexes or use cobalt(II) as a spectroscopic probe. The data relative to electronic, EPR, MCD, NMR spectra as well as to magnetic susceptibility measurements are interpreted within an Angular Overlap approach. Energy level diagrams are employed to calculate the electronic spectra and then, applying the relevant perturbation μ, g, A values are calculated for different chromophores in different coordination environments. The underlying theory is sketched paying in every case much attention to show the possibility of calculating the electronic properties in low symmetry environments. An extensive compilation of available experimental data is presented. The chromophores are classified according to the coordination number and according to the donor atom set.