Transport properties of the CexY1−xPt alloy system: Unusual concenration dependence of the Curie temperature

In order to study Kondo ferromagnetism of CePt, we have investigated the transport properties, resistivity and thermopower, of the CexY1-xPt alloy system from 2 K to 320 K. The extracted magnetic contribution to the total resistivity cannot be scaled to the concentration and is much higher than in the CexLa1-xPt alloy system. The maximum of the magnetic contribution of the resistivity moves to lower temperatures with decreasing the Ce content while the temperature of the minimum of the thermopower does not change with concentration. These two facts seem to be in contradiction. Usually one assumes that these extrema represent the Kondo temperature. To the contrary, we show that the Kondo temperature increases with decreasing Ce content. The most intriguing observation in this alloy system is the linear relationship between the Curie temperature and the concentration of the Ce ions and, moreover, that it is the same as in CexLa1-xPt. This fact is in contradiction with the conventional picture of small moment Kondo magnetism.