THE EFFECT OF MAGNETIC-FIELD AND AL CONTENT ON RESISTIVITY AND THERMOPOWER OF Y(ALXCO1-X)(2) ALLOYS

We present experimental results on thermopower (S) and electrical resi stivity (rho) of Y(AlxCo1-x)(2) compounds, with 0 less than or equal t o x less than or equal to 0.15. The properties were measured in the te mperature range from 2 up to 300 K, in the longitudinal magnetic held (H) from 0 to 15 T. These are the first measurements of thermopower fo r these alloys (for x > 0). Our results show that with increasing Al c ontent the Co 3d peak in density of states narrows. This narrowing occ urs mainly due to increasing localisation of Co 3d electrons caused by the disorder within Co sublattice. At low temperatures the scattering by spin fluctuations dominates the transport properties of the compou nds with x < 0.01. The magnetoresistivity Delta rho/rho = (rho(T,H) - rho(T,0))/rho(T,0) is positive. The magnetothermopower Gamma S = S(H) - S(0) reveals a maximum at almost the same temperature as the minimum of S(0), at this temperature Delta S similar to H-2. Delta S decrease s with Al content as does S(0), whereas the impurity contribution to t he resistivity dramatically increases. At x > 0.01, a large positive m aximum develops in the thermopower instead of the minimum and Delta S vanishes. (C) 1998 Elsevier Science B.V. All rights reserved.