Resistivity and Magnetoresistance of Dilute Alloys of Iron in Mo_0.8Nb_0.2

Abstract

The resistivity vs. temperature and resistivity vs. magnetic field have been measured for nine dilute alloys of iron in Mo_0.8Nb_0.2. Iron concentrations ranged from 0.2 to 2.3 %. Minima are observed in the resistivity vs. temperature curves in the range 28°K to 38°K, depending on iron concentration. It is found that both the temperature-independent impurity scattering and the spin scattering are linear functions of iron concentration for low concentrations, and the spin resistivity is a logarithmic function of temperature. The magnetoresistance is negative in all cases, and follows the approximate law Δρ = AH ^x, where the exponent x tends toward the value 2 for infinite dilution, and is smaller for finite values of the concentration. These results lend support to a recent theory by J. Kondo, which predicts both the linear dependence of the spin scattering on concentration, and its logarithmic dependence on temperature. If this theory is used, the s-d exchange integral is found to be negative and equal to -0.2 eV.