In the most common 2θ/θ measurement in X-ray diffractometry, the crystal lattice planes parallel to the sample surface are observed. On the other hand, in the in-plane measurement that scans the counter axis parallel to the sample surface, the crystal lattice planes perpendicular to the sample surface are observed. When these two scanning methods are used, the crystal lattice of the sample can be observed from the two directions. By comparing the indices of the crystal lattice observed by the 2θ/θ measurement and the in-plane measurement, the three-dimensional orientation state of the sample can be evaluated.
Figure 1(a) shows the 2θ/θ measurement result of a cobalt (Co) magnetic thin film on a hard disk using Rigaku's SmartLab multipurpose diffractometer. In the 2θ/θ measurement in which X-rays enter deep inside the sample, not only the Co (110) crystal lattice plane (cobalt is a hexagonal crystal), but also the diffraction peaks from aluminum (Al) and chromium (Cr) from the substrate and a halo from the amorphous NiP are observed.
Figure 1(b) shows the result when the crystal lattice planes perpendicular to the sample surface are measured using in-plane measurement. In figure 1(b), the crystal lattice planes such as Co (100), (002) and (101) that are perpendicular to the Co (110) crystal lattice plane are observed. The two profiles represent the results of which crystal lattice planes of a hard disk in the circumferential and radial directions are measured, respectively. By comparing the Co (002) diffraction peak intensities, it is found that the Co layers are in the state of in-plane orientation along the circle of the c axis shown in Figure 1(c).