Development of NanoCAP (nano composite advanced particles) technology for high density recording
In this paper, nanosized spherical magnetite particles, with the coercivity force of about 3000 Oe was developed. This material was named NanoCAP (nano composite advanced particles). This study described both magnetic and structural properties of NanoCAP. The crystal structure and the microstructure of the particles were examined using an X-ray diffractometer and high resolution transmission electron microscope, respectively. The obtained magnetization and coercivity of the particles were 89 emu/g and 2900 Oe, respectively. NanoCAP is expected to be the most promising candidate for ultrahigh capacity recording tapes.
Magnetic Properties of Fe16N2 Fine Particles.
Heat conditions for synthesis of Fe16N2 tine particles and the resulting magnetic properties were investigated. Commercial ultra fine γ - Fe2O3 particles were first reduced under hydrogen gas at temperatures between 200°C and 700°C for 8 hours and nitrided under an ammonia-argon mixed gas at 140°C for 24 hours. The powder reduced at 500°C and nitrided at 140°C was identified as nearly Fe16N2 single phase by X-ray diffraction and Mossbauer analysis. Saturation magnetization at room temperature was about 200 emu/g. Maximum coercive force (2250 Oe) was achieved in the Fe16N2 powder with the largest specific surface area.
Synthesis of Iron Nitrides FexN(x:2, 2-3, 4, 16/2)by Nitrogenizing α-Fe in Ammonia Gas, and Magnetic Properties of The Bulk Sample of Fe16N2
Iron nitrides were prepared by nitrogenizing α-iron in ammonia gas at temperatures from 100°C to 700°C. In the case using iron foils as a starting material, Fe2-3N and Fe4N were formed as a main crystal phase at the temperature ranges of 450-700°C and 250-400°C, respectively. A crystal phase like to Fe16N2 was formed at 210°C, but its XRD and Mossbauer data were too insufficient to identify as Fe16N2. While bulk Fe16N2 was formed by nitrogenizing iron fine powder with the diameter of about 20nm at 110°C for 10days, but small amounts of Fe3N coexisted as a second phase with Fe16N2 at 120°C for 10days. Crystal structure of Fe16N2 was refined by Rietveld method. The average magnetic moment of three kinds of Fe atoms in Fe16N2 was evaluated to be 2.52μB on the basis of its Mossbauer data, the value of which was larger by 15% than the magnetic moment of α-Fe. The saturation magnetization of the Fe16N2 powder was also larger by about 14% than that of the α-Fe powder before nitrogenizing.