Atomic physics at the planned new RIKEN facility

Combining Mössbauer spectroscopy with magnetic property measurement, we have studied Fe-N and (Fe, Ni)-N powders for magnetic recording. The typical particles of the core (α-Fe)/shell (γ′-Fe₄N) structure have been successfully prepared. All the products are stabilized in a multi-organic solution. It has been found that the coercivity can be changed from 300 to 800 Oe by adjusting the shape of the particles. The special saturation magnetization of the particles can be adjusted from 120 to 180emu/g and their chemical stability is improved by substituting nickel for iron in γ′-Fe₄N. Following experiments for corrosion resistance, it is expected that (Fe, Ni)-N and the core/shell particles will be applied as recording media in the near future.