Amorphous Ultrafine Metallic Particles

A review on the preparation method of amorphous ultrafine metallic particles and their magnetic properties is given; sputter-etching an appropriate polymer substrate produces a densely-packed array of needle-1ike projections on the polymer surface. RF sputter deposition of an adequate alloy onto this surface produces an array of elongated finger-like projections of amorphous magnetic materials, with diameter well under 1μm and aspect ratios of 5 or more. These finger-like projections meet the definition of ultrafine particles(UFP). Planar samples prepared in this way have a magnetic easy axis perpendicular to the sample surface with K_u/2πM_s^2=0.1～0.2, and have coercive field up to 700 Oe. A maximum coercive field of almost 1200 Oe is obtained for annealed samples at about 500℃. The anisotropy varied linearly with M_s^2, suggesting that its origin is largely the shape anisotropy of the particles. Furthermore, the coercive field varied linearly with K_u/M_s, as predicted by a Stoner-Wohlfarth single domain model. An attempt is made to these particles film as a perpendicular recording media

Magnetic Properties of Amorphous Fe-Zr-B Alloys

The formation range, magnetic properties and thermal stability for Fe-Zr-B amorphous alloys have been examined. The combination of zirconium and boron as glass formation elements is extremely effective both in expanding the formation range and increasing stability against crystallization for Fe-based amorphous alloys. Both the Curie temperature and saturation magnetization at room temperature decrease with increasing Zr content. Magnetostriction for the present alloys is smaller than that of metal-metalloid alloys possessing the same magnitude of saturation magnetization. There is no variation in coersive force on isothermal aging at 150℃ for time up to 10^4 minutes

Nanostructure characterization of Co–Pd–Si–O soft magnetic nanogranular film using small-angle X-ray and neutronscattering

The nanostructure of a Co–Pd–Si–O nanogranular film was investigated with the combined use of small-angle x-ray (SAXS) and neutron scattering (SANS). Using a new, compact type of SANS instrument, the SANS profiles of individual particles with a diameter of about 2–4 nm were successfully observed. The structures of magnetic regions were found to be the same as the chemical structures of the particles, and a sharp interface was observed between the matrix and the particles. The SAXS to SANS ratio clearly indicates that the particles are a CoPd alloy and the matrix is not pure SiO2. In fact, the matrix is composed of a meaningful amountof Co

Selective Product of Magnetite through Addition of Small Amount of Metal Element

In this study, we investigate the transformation mechanism from a phase mixture of magnetite (Fe3O4) and hematite (α-Fe2O3) to a single-phase magnetite through the addition of a specific metal element. The thin films were prepared by rf sputtering with a composite target of metal chips set on a ceramic magnetite (or hematite) target in Ar atmosphere. It is revealed that the addition of Ge to the polycrystalline hematite film obviously produces single-phase magnetite, indicating that the hematite is fully transformed to magnetite through an addition of Ge. Such transformation is also seen with slight additions of Mo, W, Cr, and Mg, whereas the addition of Sn does not affect the phase mixture of magnetite and hematite. According to the free energy of the reaction, elements of Ge, Mo, W, Cr, and Mg are capable of reducing hematite, whereas hematite remains unreactive with addition of Sn. This is in good agreement with the experiment results. This unique technique additionally provides the maximum magnetization of 3.9 kG at 8 ×105 A·m-1(10 kOe) at a Mo concentration of 1.3 at. %. </jats:p