EFFECT OF VOLUME VARIATION ON THE PROPERTIES OF THE KONDO SYSTEM (LA1-XCEX)(3)AL

We have measured the electrical resistivity and ac magnetic susceptibi lity (chi)(T) of (La1-xCex)(3)Al, for 0 less than or equal to x less t han or equal to 1, and the electrical resistivity of (Ce1-zYz)(3)Al, f or 0 less than or equal to z less than or equal to 0.1. The system was characterized using x-ray diffraction and metallography. From x-ray d ata we were able to determine the structure for all samples to be hexa gonal and that the unit-cell volume decreases linearly in going from t he La-rich side to the Ce-rich side. The results show that La3Al is a superconductor below 6.2 K a:nd that T-c decreases rapidly with the in crease of the Ce concentration. For x > 0.04 we observed a minimum in the resistivity and a reduction of the effective magnetic moment of Ce due to a strong compensation promoted by the Kondo effect. Our result s show that the Kondo temperature increases with Ce and Y concentratio n, according to the reduction of the unit-cell volume. We also show th at the antiferromagnetic transition temperature goes through a maximum at z = 0.025, indicating that there is an interplay between supercond uctivity, antiferromagnetic ordering, and the Kondo effect. A diagram illustrating the evolution of the T-K and T-N is :presented. The elect ronic specific heat (gamma) increases with the Ce concentration showin g a maximum around x approximate to 0.4. It was also possible to deter mine values for the rho J product and the relative variation of the ex change parameter.