Kondo Phenomenon in Dilute Lanthanum-Cerium Solid Solutions

The manifestations of the Kondo effect in lanthanum-rich fcc lanthanum-cerium solid solutions, containing 0.9, 2.0, 2.5, 3.9, 6.0, 6.5, and 8.5 at.% Ce, have been studied by electrical transport property measurements. The electrical resistivity data as a function of temperature between 4° and 30°K clearly reveal a resistivity minimum in all above-mentioned alloys. The temperature at which the minimum occurs is almost independent of cerium concentration: it gradually changes from 5.8°–7.4°K, associated with 0.9 at.% Ce- and 8.5 at.% Ce-alloy, respectively. The depth of the resistivity minimum, measured with respect to 4.2°K, increases from 0.01 μΩ-cm (0.9 at.% Ce) to 0.13 μΩ-cm (8.5 at.% Ce) with increasing cerium content. The additional electrical resistivity due to dissolved cerium in lanthanum is proportional to ln T, where T is the absolute temperature, for temperatures below 12°K. The total electrical magnetoresistivity studies at 4.2°K, made with longitudinal magnetic fields up to 60 kOe, show the following behavior: The resistivity increase with increasing fields is positive for pure normal lanthanum, almost independent of field for 0.9 at.% cerium alloy, and negative for all other lanthanum alloys. The absolute value of the magnetoresistivity increases with increasing cerium concentration. All these observations result from the localized magnetic moments associated with cerium dissolved in lanthanum.