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Journal Article

Microscopic model for the semiconductor-to-ferromagnetic-metal transition in FeSi(1-x)Ge(x) Alloys


Lauchli,  A. M.
Max Planck Institute for the Physics of Complex Systems, Max Planck Society;

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Yang, K. Y., Yamashita, Y., Lauchli, A. M., Sigrist, M., & Rice, T. M. (2011). Microscopic model for the semiconductor-to-ferromagnetic-metal transition in FeSi(1-x)Ge(x) Alloys. EPL, 95(4): 47007.

Cite as: https://hdl.handle.net/11858/00-001M-0000-0029-8C61-C
The simplified band structure introduced by Mazurenko et al. to model FeSi is used to analyze the singlet semiconductor to ferromagnetic metal transition in the isoelectronic isostructural alloys, FeSi(1-x)Ge(x). The complex band structure of the alloy is replaced by an alternating chain of doubly and singly degenerate atoms to represent Fe and Si/Ge, respectively. The former (latter) form narrow (broad) bands with a substantial hybridization between them. A substantial onsite repulsion including Hund's rule coupling is introduced on the Fe sites. The mean-field phase diagram contains a first-order phase transition from the singlet semiconductor to a ferromagnetic metal with increasing temperature and interaction strength, similar to the alloys. The analysis also reproduces the rapid rise of the spin susceptibility in the semiconductor with a crossover to a Curie-Weiss form at higher temperatures. Good agreement is found at zero temperature between the mean-field and accurate DMRG calculations. Copyright (C) EPLA, 2011