Orientational dependence of exchange anisotropy of Mn-Ir/Co-Fe epitaxial bilayers

摘要

The exchange anisotropy of pseudo-single crystalline Mn-Ir/Co-Fe bilayers with different crystallographic orientations, such as (110), (001), and (111), was investigated. As a result, we found that the unidirectional anisotropy constant J_(K) strongly depends on the crystallographic orientation, while the critical thickness of the antiferromagnetic layer d_(AF)~(cr) is similarly ～3 nm. As a notable result, the J_(K) of the (110)-epitaxial bilayer with d_(AF)=4 nm shows extra large value of 0.73 erg/cm~(2). The magnetic anisotropy of the Mn-Ir layer determined from the saturation torque amplitude was 8.5×10~(5) erg/cm~(3) for the (110) bilayer, 5.0×10~(4) erg/cm~(3) for the (001) bilayer, and 10~(3)-10~(4) erg/cm~(3) for (111) bilayer, respectively. From the correlation between the exchange anisotropy and the magnetic anisotropy of the Mn-Ir layer, we conclude that the domain wall model is inadequate to explain these experimental results and the single spin model can do it qualitatively, assuming that the interfacial exchange coupling energy differs in the respective crystallographic orientation.