Anisotropy in the Kondo effect of single crystal Zn–Mn alloys

Abstract

The anisotropy in the Kondo effect of single crystal ZnMn alloys (10–500 at. ppm Mn) has been studied between 0.3 and 8 K. The impurity resistivity with current flowing perpendicular to the c-axis of the hexagonal crystal is 1.6 times greater than the impurity resistivity with the current flowing parallel to the c-axis for all the ZnMn alloys. The resistivity of a Zn 500 at. ppm Al alloy was found to be isotropic and, in agreement with previous results, the resistivity of pure zinc was found to be nearly isotropic. On the basis of a two band model for zinc we show that the ratio the relaxation time on the monster and lens portions of the Fermi surface τL/τM is 1.3 ± 0.1 for pure Zn, 1.1 ± 0.3 for the ZnAl alloy, and 0.43 ± 0.05 for the ZnMn alloys. We attribute the threefold variation of τM/τL between magnetic Mn (d-type) impurities and the nonmagnetic (s,p-type) impurities in pure Zn and the ZnAl alloys to the nature of the conduction electron wave functions on the monster and lens portions of the Fermi surface of Zn. We require the partial density of s,p-like wave functions to 1.2 times greater on the lens surface than on the monster surface while the partial density of d-like wave functions on the lens surface must be 0.4 times their density on the monster surface.