SUPPRESSION OF THE GAP ENERGY IN ZR-NI-SN AND TI-NI-SN BY PARTIAL SUBSTITUTION OF ZR AND TI BY CE

We report on magnetic measurements and electronic structure investigat ions of the alloyed compounds Zr-Ni-Sn and Ti-Ni-Sn. Both belong to th e group of semi-Heusler alloys, and are classified as narrow-gap semic onductors with indirect gaps near 500 meV. Tetravalent ions (Zr,Ti) ar e partly replaced by Ce, with a Ce concentration less than 20%. Suscep tibility measurements indicate the magnetic ground state of Ce in both Zr-Ni-Sn and Ti-Ni-Sn, and the effective moment is near the trivalent value at T=300 K. The Ce 4f(1) configuration is well accepted by Ce 3 d x-ray photoemission spectra. We compare the x-ray photoemission spec troscopy valence-band spectra for investigated Ce alloys. A very good agreement between the experiments and calculations is obtained. We cla ssify Zr-Ni-Sn and Ti-Ni-Sn as alloys with a strong hybridization infl uence on the gap formation. The destructive alloying affecting the gap stability seems to have the same origin as in the case of Ce Kondo in sulators. [S0163-1829(98)07115-X].