New soft magnetic material of α′-Fe-C with high B_s

Epitaxial Fe-C films consisting of an α′-Fe-C single phase with a C content up to 12 at% can be synthesized on MgO single crystal substrates by sputtering. The saturation magnetization for the α′-Fe-C films maintains a constant value of about 210 emu/g (≈ 2.1 T) up to 8 at% C. The easy axis of magnetization of α′-Fe-C films lies in the (0 0 1) plane. The uniaxial magnetocrystalline anisotropy constant for α′-Fe-C is -0.5 × 10⁶ erg/cm³ independent of the C content. The coercive force for the α′-Fe-C films with C content more than 4 at% is about 2 Oe. The α′-Fe-C films with 4-8 at% C are promising candidates for use as writing head material.