Magnetocrystalline anisotropy for α′-Fe-C and α′-Fe-N films

Structural and magnetic analyses were made for alpha ' -Fe-C (0-12 at.%C) and alpha ' -Fe-N(0-12 at.%N) films. The results are summarized as follows: 1) epitaxial Fe-C films consisting of an alpha ' -Fe-C single phase with a C content up to 12 at.% can be synthesized on MgO single crystal substrates by sputtering. 2) the change in lattice constants,a and c, as a function of the C content for the alpha ' -Fe-C phase was found to be the same as that of the alpha ' -Fe-N against the N content. 3) the saturation magnetization for the alpha ' -Fe-C films maintains a constant value of about 210 emu/g (approximate to 2.1 T) up to 8 at.%C. 4) the easy axis of magnetization of alpha ' -Fe-N corresponds to the c-axis of the bet structure. Even though the alpha ' -Fe-C phase has the same bet structure as the alpha ' -Fe-N, the easy axis of magnetization Hes in the (001) plane. 5) the value of the uniaxial magnetocrystalline anisotropy, K-u for alpha ' -Fe-C is -2 x 10(6) erg/cm(3) independent of the C content, and the magnetocrystalline anisotropy constant, K-3 decreases with increasing C content and is about 3 x 10(5) erg/cm(3) at 12 at.% C. 6) the value of the coercive force for the alpha ' -Fe-C films with C content more than 4 at.% is about 2 Oe. From this study, it is found that the alpha ' -Fe-C films with 4-8 at.%C are promising candidates for use as writing head material.