Modified Zener Model for Ferromagnetism in Transition Metals and Alloys—Model Calculations ofTC

An essential feature of the modified Zener model for ferromagnetism in transition metals and alloys is the coupling of an itinerant $d$ electron to a localized spin in accordance with Hund's rule. In contrast to the Stoner-Wohlfarth model for ferromagnetism, this model takes into account the Hund's-rule effects and the orbital degeneracy of the $d$ electrons. The exchange-enhanced dynamic susceptibility is calculated, and from its singularity in the static long-wavelength limit, the Curie temperature $T_C$ is calculated as a function of bandwidth, the exchange interactions, and the number of itinerant $d$ electrons per atom where a fcc tight-binding density of states is assumed. The results of the model calculation of $T_C$ are compared to results for a pure itinerant-electron ferromagnet of the Stoner-Wohlfarth type and compared to experimental results for $T_C$ as a function of pressure. The calculated $T_C$ is found consistent with the experimental data. The unusual excitation spectrum for the modified Zener model is also discussed.