Polarization tunability and analysis of X-rays is one of the most advancing
features of third-generation synchrotron radiation sources. In order to ap
ply such developments to the observation of magnetic effects, a diffractome
ter for X-ray magnetic absorption and scattering experiments was constructe
d on BL39XU at SPring-8. The efficiency of the apparatus is clearly demonst
rated by several observations of the magnetic effects. In particular, a dia
mond phase plate plays an essential role in regulating both circular and li
near polarization states.