Effect of Al_2O_3 Additive on the Soft Magnetic Properties of High-B_s Fe-Co-Al-O Films on a Thin Underlayer

摘要

To understand the origin of the soft magnetic properties of Fe-Co system films with a high saturation magnetic flux density (B_s), structural analysis was performed by conducting detailed X-ray diffraction (XRD) measurements and transmission electron microscope (TEM) observations in a wide range of film thicknesses and Al_2O_3 compositions. An initial growth layer with small grains, a continuous columnar structure, and alternation of the crystal orientation according to the film thickness are important for obtaining good soft magnetic properties in a wide range of film thicknesses. These features can be obtained by using a combination of an Al_2O_3 additive of about 1-3 at percent and a thin underlayer. The mechanism of the soft magnetic properties of Fe-Co system films seems to be partially explained by the existence of an initial growth layer with good soft magnetic properties and the exchange-coupling effect with the initial growth layer.