Kondo Effect in a Magnetic Field and the Magnetoresistivity of Kondo Alloys

The effect of a magnetic field on the spectral density of a S = 1/2 Kondo impurity is investigated at zero and finite temperatures by using Wilson's numerical renormalization group method. A splitting of the total spectral density is found for fields larger than a critical value H_c\(T = 0\)~0.5T_K, where T_K is the Kondo scale. The splitting correlates with a peak in the magnetoresistivity of dilute magnetic alloys which we calculate and compare with the experiments on Ce_xLa_1-xAl₂,x = 0.0063. The linear magnetoconductance of quantum dots exhibiting the Kondo effect is also calculated.