Effect of crystallographic orientation of Co2MnGe Heusler-alloy film on its surface roughness and ordered structure

The effects of direction and degree of preferred orientation of Co2MnGe film on the surface roughness and the ordered structure were investigated by utilizing various buffer layers and underlayers. Degrees of preferred orientation of Co2MnGe film were estimated by measuring the full width at half maximum (FWHM) of the x-ray diffraction rocking curve for Co2MnGe(400) or Co2MnGe(220) reflections. A high B2 ordered structure and a high saturation magnetization, which is almost the same value as in the case of epitaxial Co2MnGe films, were obtained regardless of the direction and degree of preferred orientation, except in the case of the Co2MnGe films without both buffer layers and underlayers. Also, surface roughness decreased when decreasing the FWHM of x-ray diffraction rocking curve, and the small surface roughness (that is almost the same value as in the case of epitaxial Co2MnGe films) was obtained for Co2MnGe films with the high degree of preferred orientation. A smaller surface roughness was obtained in the case of Co2MnGe films with (110) preferred orientation compared with the Co2MnGe(100) case. The tendencies of change of the surface roughness were explained from the viewpoint of surface energy. (c) 2007 American Institute of Physics.