Disordered compounds electronic band structure

Various interesting properties of 4f-electron systems such as CK and HF compounds have been generally studied using crystalline materials, where there is also periodicity of 4f electrons. The formation of the Fermi surface from 4f-electron bands is essential to many, if not all of these cooperative properties. Therefore, such behaviors are not expected to occur in disordered alloys without translational symmetry where the 4f electrons have non-Bloch-type states. However, interesting behaviors have recently been observed in Ce-based structurally disordered materials. Here, we introduce amorphous CeRu system as a typical example. Crystalline CeRu2 compoimd is one of the famous itinerant 4f-electron materials to show SC (T = 6.3 K, y = 27 mj/mol K ) (Hedo et al., 1998 Matthias et al., 1958). On the other hand, amorphous fl-CeRu also shows FlF-like behavior in the Ce-rich side and SC in the Ru-rich side (Homma et al., 1997). 

Since the EFG is a very sensitive function of the molecular and crystal structure, the resonance frequencies and band shapes are specific to each compound, and NQR data can be used for determining unambiguous sample identification, local electronic structure, atomic arrangement, order/disorder phenomena, and crystal phase transformations. In addition, molecular dynamics in the solid state can be studied. Furthermore, since NQR data are sensitive to changes in temperature and pressure, there is the possibility of obtaining strain information. 

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