Anisotropic soft X-ray emission spectroscopy study of the valence electron state of Lu(Al, T )B 4 ( T = Cr, Mn, Fe, Mo) exhibiting two-dimensional B-layers

Lu(Al, T )B 4 ( T = Cr, Mn, Fe, Mo) have the alternate stacking structure of B-layer and Lu(Al, T )-layer along the c -axis. B-K emission spectra of these materials are measured at two take-off angles of 20° and 70° from the c-plane. The energy region corresponding to the top of valence band (VB) shows a larger spectrum intensity at the smaller take-off angle, responsible for p z character. The bottom region shows the opposite angle dependence, responsible for p x and p y character. The middle of the VB of a large peak intensity shows almost no angle dependence, suggesting an isotropic distribution of bonding charge. As a whole, the angle-dependence of the B-K emission intensity is smaller than that of graphite. This rather isotropic bonding-charge distribution of the boron-layer can make the inter-layer bonding between B-layer and adjacent Lu(Al, T ) layer and is presumably related to the hardness of those bulk materials.