Role of s−d Exchange Interactions in Dilute Alloys Exhibiting Both Low-Temperature Resistance Anomalies and Superconductivity

Measurements of the magnetic susceptibility of some dilute Zn-Mn alloys are reported in the temperature range where this alloy system is known to exhibit low-temperature resistance anomalies. All of the alloys studied obey a Curie law with the most concentrated alloy (0.43-at.% Mn) exhibiting deviations in the neighborhood of 6^∘{}K. The Curie constant indicates that manganese when dissolved in zinc has a spin value of 2/3 which is temperature-independent between 5 and 273^∘{}K. Calculations of the exchange integral J from the magnetic properties of dilute Zn-Mn alloys have been made from the N\'eel temperature, the magnetoresistivity as a function of field strength and the suppression of the superconducting critical temperature based on theoretical equations which assume a scalar s-d interaction between the paramagnetic ions and conduction electrons. All of the derived values of J lie in the range of (1.4±{}0.2)×{}10^-12 erg which would lead one to conclude that the magnetic interaction giving rise to these various effects is of the same nature. A graphical method for separating the resistance minimum from the total resistivity, in the presence of a resistance maximum produced by magnetic ordering in the Zn-Mn system, is presented.