First-Principles Dynamical Coherent-Potential Approximation Approach to the Ferromagnetism of Fe, Co, and Ni
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概要
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Magnetic properties of Fe, Co, and Ni at finite temperatures have been investigated on the basis of the first-principles dynamical coherent potential approximation (CPA) combined with the local density approximation (LDA) + U Hamiltonian in the tight-binding linear muffintin orbital (TB-LMTO) representation. The Hamiltonian includes the transverse spin fluctuation terms. Numerical calculations have been performed within the harmonic approximation with 4th-order dynamical corrections. Calculated single-particle densities of states in the ferromagnetic state indicate that the dynamical effects reduce the exchange splitting, suppress the band width of the quasi-particle state, and causes incoherent excitations corresponding the 6 eV satellites. Results of the magnetization vs temperature curves, paramagnetic spin susceptibilities, and the amplitudes of local moments are presented. Calculated Curie temperatures (T_{\text{C}}) are reported to be 1930 K for Fe, 2550 K for Co, and 620 K for Ni; T_{\text{C}} for Fe and Co are overestimated by a factor of 1.8, while T_{\text{C}} in Ni agrees with the experimental result. Effective Bohr magneton numbers calculated from the inverse susceptibilities are 3.0 \mu_{\text{B}} (Fe), 3.0 \mu_{\text{B}} (Co), and 1.6 \mu_{\text{B}} (Ni), being in agreement with the experimental ones. Overestimate of T_{\text{C}} in Fe and Co is attributed to the neglects of the higher-order dynamical effects as well as the magnetic short range order.
- 2011-03-15
著者
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Kakehashi Yoshiro
Department Of Physics And Earth Sciences Faculty Of Science University Of Ryukyus
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Kakehashi Yoshiro
Department of Physics and Earth Sciences, Faculty of Science, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213, Japan
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Patoary M.
Department of Physics and Earth Sciences, Faculty of Science, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213
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