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.
Magnetic and Mössbauer studies of single‐crystal Fe16N2 and Fe‐N martensite films epitaxially grown by molecular beam epitaxy (invited)
Single‐phase, single‐crystal Fe16N2(001) films and Fe‐11 at. %N martensite films of 200–900 A thickness have been epitaxially grown on In0.2Ga0.8As(001) substrates by evaporating Fe in an atmosphere of mixed gas of N2 and NH3, followed by annealing. The saturation magnetizations 4πMs’s for Fe16N2 and Fe‐N martensite films have been measured to be around 29 and 24 kG at room temperature, respectively, and almost constant in the above thickness range by using a vibrating sample magnetometer. 4πMs for Fe‐N martensite films has been increased with ordering of N atoms caused by annealing and finally reached around 29 kG for Fe16N2. Mossbauer spectra have been measured for those films. The spectrum for Fe‐N martensite films was a superposed one with hyperfine fields of 360, 310, and 250 kOe, similar to those previously reported for martensite. While the spectrum became simpler with ordering, finally reaching a single hyperfine field of 330 kOe for Fe16N2. 4πMs of 29 kG for Fe16N2 (3.2 μB/Fe atom) and 4πMs of 24...