Fabrication of nanogranular flakes of magnetic metallic nanoparticles in an oxide matrix
- PDF / 648,229 Bytes
- 10 Pages / 584.957 x 782.986 pts Page_size
- 74 Downloads / 191 Views
Novel nanogranular flakes in which magnetic metallic nanoparticles are highly dispersed in an oxide matrix were fabricated for use as a constituent material in bulk nanogranular composites. A simple milling process using core/shell nanoparticles of magnetic metal/oxide was used to produce nanogranular flakes composed of magnetic metallic nanoparticles in an oxide matrix. The high dispersion of the metallic nanoparticles in the oxide matrix increased the electrical resistivity of the flakes. In addition, neighboring nanoparticles in the flakes interacted with each other via magnetic exchange coupling, and the flakes exhibited good soft magnetism with low coercivity when they contained a high concentration of highly dispersed magnetic metallic nanoparticles. The coercivity of the flakes could be decreased significantly by annealing and by modifying the surface of the flakes. A minimum coercivity of 8.7 Oe was obtained using flakes with a composition of Fe0.5Ni0.5–4 wt% Si. I. INTRODUCTION
Recently, there has been increasing demand for power supply devices and systems to be made smaller by increasing the working frequency to the megahertz band and to control higher levels of electric power by using silicon carbide or gallium nitride power semiconductors.1,2 In devices and systems that control high levels of electric power at high working frequencies, soft magnetic components such as inductors and transformers must be able to control the high magnetic fluxes that accompany the electric power. The soft magnetic materials used in these components require high permeability, high saturation magnetization, and low magnetic loss at high frequencies in the megahertz band. High saturation magnetization is necessary to prevent magnetic saturation particularly in devices and systems that control high levels of electric power. Magnetic loss is mainly composed of hysteresis loss and eddy-current loss. Low coercivity is necessary to reduce hysteresis loss, and high electrical resistivity is necessary to reduce eddy-current loss. Low coercivity can also contribute to high permeability when low coercivity is achieved through low magnetic anisotropy, which can produce high permeability. In general, there are two kinds of magnetic materials: magnetic metals and magnetic oxides, the latter of which are called ferrites. Magnetic metals have high saturation magnetization but low electrical resistivity, which causes
Contributing Editor: Michael E. McHenry a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2016.410
high eddy-current loss at high frequencies. In contrast, ferrites have high electrical resistivity but low saturation magnetization. One structure that is able to offer both high saturation magnetization and high electrical resistivity is a nanogranular structure composed of magnetic metallic nanoparticles that have a high saturation magnetization in an insulating matrix that has high electrical resistivity. Magnetic nanogranular thin films have been fabricated and their effectiveness has
Data Loading...
