Low-Temperature Properties of Dilute Ferromagnets in Copper

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Abstract
The low-temperature properties of dilute magnetic impurities in copper are studied, using an extension of the recently developed statistical theory of Klein and Brout. A Ruderman-Kittel (RK) interaction is assumed to exist between the magnetic impurities. The probability distribution of the effective field about an impurity, due to all other impurities of the system, is obtained. The variation of the probability distribution as a function of the impurity concentration, temperature, and J S2, where J is the strength of the Ruderman-Kittel interaction and S is the magnitude of the impurity spin, is briefly discussed. Using this distribution function, we show that the model explains the low-temperature specific heat of dilute copper-cobalt and copper-iron. Copper-magnanese has been explained previously by the same model. The fact that the Ruderman-Kittel potential explains the low-temperature specific heat of all three substances gives additional support to the theory that this potential, rather than Overhauser's spin-density waves, is the correct interaction mechanism between dilute magnetic impurities in a nonmagnetic conductor. The detailed shape of the probability distribution and its variation with temperature is in qualitative agreement with recently obtained Mössbauer data on dilute Cu–Fe.