Ferromagnetism in a dilute magnetic semiconductor -- Generalized RKKY interaction and spin-wave excitations

Abstract

Carrier-mediated ferromagnetism in a dilute magnetic semiconductor has been studied using i) a single-impurity based generalized RKKY approach which goes beyond linear response theory, and ii) a mean-field-plus-spin-fluctuation (MF+SF) approach within a (purely fermionic) Hubbard-model representation of the magnetic impurities, which incorporates dynamical effects associated with finite frequency spin correlations in the ordered state. Due to a competition between the magnitude of the carrier spin polarization and its oscillation length scale, the ferromagnetic spin coupling is found to be optimized with respect to both hole doping concentration and impurity-carrier spin coupling energy $J$ (or equivalently $U$). The ferromagnetic transition temperature $T_c$, deteremined within the spin-fluctuation theory, corresponds closely with the observed $T_c$ values. Positional disorder of magnetic impurities causes significant stiffening of the high-energy magnon modes. We also explicitly study the stability/instability of the mean-field ferromagnetic state, which highlights the role of competing AF interactions causing spin twisting and noncollinear ferromagnetic ordering.

10 pages, 12 figures

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• Monte Carlo simulation of magnetic phase transitions in Mn doped ZnO
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• Carrier induced ferromagnetism in diluted local-moment systems
• Non-Linear Spin Susceptibility in Topological Insulators
• Spin exchange interaction with tunable range between graphene quantum dots
• Spin waves in a band ferromagnet: spin-rotationally symmetric study with self-energy and vertex corrections
• Spin dynamics in the diluted ferromagnetic Kondo lattice model
• Clustering induced suppression of ferromagnetism in diluted magnets
• Twisted light-induced spin-spin interaction in a chiral helimagnet
• Impact of Next-Nearest-Neighbor hopping on Ferromagnetism in Diluted Magnetic Semiconductors
• Disordered Correlated Kondo-lattice model
• RKKY interaction in Mn-doped 4 $\times$ 4 Luttinger systems
• Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction in Weyl semimetals with tilted energy dispersion
• Highly tunable magnetic coupling in ultrathin topological insulator films due to impurity resonances