Anomalous Density of States in Dilute Magnetic Alloys

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An interaction between conduction electrons is derived based on the s-d interaction model for dilute magnetic alloys. The interaction results from a process in which the first electron excites a localized spin and the second one deexcites the same spin. Thus it is a consequence of the dynamical character of the s-d interaction. Special circumstances for dilute alloys make the interaction large and we find that the thermal mass of the conduc­ tion electrons, when the electron-electron interaction is taken into account, becomes several times larger than the free mass below the Neel temperature. This seems to account for the anomalous specific heats of dilute magnetic alloys. metals have localized magnetic moments, and consequently the origin of the anomalies may be ascribed to exchange interaction between spins of the con­ duction electrons and the impurity ·atoms. A remarka.ble thing about this, so called, s-d interaction is that it is a dynamic one and consequently gives rise to an interaction between the conduction electrons. )'his interaction results from a process in which the first electron excites a localized spin and the second one deexcites the same spin. vVe have an analogy in the case of the electron­ phonon interaction, where two conduction electrons interact through emitting and absorbing a phonon. Emphasis should be laid on special circumstances for dilute alloys: The interaction between the conduction electrons will be quite large at the fermi surface, because the magnitude of the internal field for the localized spins will be rather small in view of the fact that the field arises from indirect interaction between spins of the impurity atoms. The purpose of this paper is to derive the interaction mentioned and calculate from it a mass shift of the conduction electrons, which will turn out to be significant enough to account for the observed anomalous electronic specific heat of some kinds of clilute alloys. We shall derive an electron-electron interaction from the s-d interaction, using an analogous method by which the electron-phonon interaction was elimi­ nated giving rise to an electron-electron interaction. 2 l There are, however, points to be noted in the case of dilute alloys. First, the internal field, which cor­ responds to the phonon frequency in the case of electron-phonon interaction,