The structures, electronic states and low temperature properties have been observed for amorphous Ce-Cu, Ce-Si and Ce-Ru alloys produced by sputtering. The X-ray diffraction analyses of these alloys indicate that the chemical short range structures of the amorphous Ce-Cu and Ce-Si alloys are ordered, resembling their crystalline counterparts, while that of the amorphous Ce-Ru alloy is disordered, being different from its crystalline counterpart. X-ray photoemission spectra indicate that the amorphous Ce-Cu alloy is trivalent, the amorphous Ce-Ru alloy shows hybridization between the 4f and conduction electrons (whose valence number is about 3.23) and the electronic state of the amorphous Ce-Si alloy is intermediate between those of the amorphous Ce-Cu and Ce-Ru alloys. The electronic specific heat coeffcient estimated from the specific heat above 10 K is more than a hundred times larger than those of simple metals and it rapidly increases below 5 K (a heavy fermion behavior). The electrical resistivity is large due to disorder scattering and its temperature dependence displays-logT dependence at low temperatures (an incoherent or impurity Kondo effect). However, it shows roughly AT2(A>0) dependence and positive magnetoresistance in the amorphous Ce-Ru alloy whose crystalline counterpart has a very high Kondo temperature (a coherent Kondo effect). These results demonstrate that the heavy fermion characteristics are depressed but not deleted even in random alloys.
ASJC Scopus subject areas
- Materials Science(all)
- Condensed Matter Physics
- Mechanics of Materials
- Physical and Theoretical Chemistry