Concentration and temperature dependence of electrical resistivity in Zr<inf>1-x</inf>Ho<inf>x</inf>Co<inf>2</inf> (0≤x≤1) intermetallic compounds and their hydrides

The electrical resistivity studies have been carried out on the C 15-type Laves phase intermetallic compounds Zr1-xHoxCo2 (0≤x≤1) and their hydrides in the temperature range 16-300 K. The first-order magnetic transition occurring for x=1 disappears for lower Ho concentrations. Anomalies in the form of resistivity minima observed for the intermediate x values are attributed to the spin fluctuations in the vicinity of the magnetic ordering temperature. On hydrogen absorption, the first-order transition observed for x=1.0 as well as the anomalies observed for the other x values disappear at higher hydrogen concentrations. A concentration-dependent metal-semiconductor-like transition has been observed in all cases. This may be a consequence of charge transfer taking place between hydrogen and the 3d band, which leads to a strong decrease in the conduction electron density. The activation energy is evaluated from the ln ρ vs 1/T plots.