Wannier-function approach to spin excitations in solids

E. Şaşıoğlu, A. Schindlmayr, C. Friedrich, F. Freimuth, S. Blügel, Physical Review B 81 (2010).

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Abstract
We present a computational scheme to study spin excitations in magnetic materials from first principles. The central quantity is the transverse spin susceptibility, from which the complete excitation spectrum, including single-particle spin-flip Stoner excitations and collective spin-wave modes, can be obtained. The susceptibility is derived from many-body perturbation theory and includes dynamic correlation through a summation over ladder diagrams that describe the coupling of electrons and holes with opposite spins. In contrast to earlier studies, we do not use a model potential with adjustable parameters for the electron-hole interaction but employ the random-phase approximation. To reduce the numerical cost for the calculation of the four-point scattering matrix we perform a projection onto maximally localized Wannier functions, which allows us to truncate the matrix efficiently by exploiting the short spatial range of electronic correlation in the partially filled d or f orbitals. Our implementation is based on the full-potential linearized augmented-plane-wave method. Starting from a ground-state calculation within the local-spin-density approximation (LSDA), we first analyze the matrix elements of the screened Coulomb potential in the Wannier basis for the 3d transition-metal series. In particular, we discuss the differences between a constrained nonmagnetic and a proper spin-polarized treatment for the ferromagnets Fe, Co, and Ni. The spectrum of single-particle and collective spin excitations in fcc Ni is then studied in detail. The calculated spin-wave dispersion is in good overall agreement with experimental data and contains both an acoustic and an optical branch for intermediate wave vectors along the [100] direction. In addition, we find evidence for a similar double-peak structure in the spectral function along the [111] direction. To investigate the influence of static correlation we finally consider LSDA+U as an alternative starting point and show that, together with an improved description of the Fermi surface, it yields a more accurate quantitative value for the spin-wave stiffness constant, which is overestimated in the LSDA.
Publishing Year
Journal Title
Physical Review B
Volume
81
Issue
5
Article Number
054434
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Şaşıoğlu E, Schindlmayr A, Friedrich C, Freimuth F, Blügel S. Wannier-function approach to spin excitations in solids. Physical Review B. 2010;81(5). doi:10.1103/PhysRevB.81.054434
Şaşıoğlu, E., Schindlmayr, A., Friedrich, C., Freimuth, F., & Blügel, S. (2010). Wannier-function approach to spin excitations in solids. Physical Review B, 81(5). https://doi.org/10.1103/PhysRevB.81.054434
@article{Şaşıoğlu_Schindlmayr_Friedrich_Freimuth_Blügel_2010, title={Wannier-function approach to spin excitations in solids}, volume={81}, DOI={10.1103/PhysRevB.81.054434}, number={5054434}, journal={Physical Review B}, publisher={American Physical Society}, author={Şaşıoğlu, Ersoy and Schindlmayr, Arno and Friedrich, Christoph and Freimuth, Frank and Blügel, Stefan}, year={2010} }
Şaşıoğlu, Ersoy, Arno Schindlmayr, Christoph Friedrich, Frank Freimuth, and Stefan Blügel. “Wannier-Function Approach to Spin Excitations in Solids.” Physical Review B 81, no. 5 (2010). https://doi.org/10.1103/PhysRevB.81.054434.
E. Şaşıoğlu, A. Schindlmayr, C. Friedrich, F. Freimuth, and S. Blügel, “Wannier-function approach to spin excitations in solids,” Physical Review B, vol. 81, no. 5, 2010.
Şaşıoğlu, Ersoy, et al. “Wannier-Function Approach to Spin Excitations in Solids.” Physical Review B, vol. 81, no. 5, 054434, American Physical Society, 2010, doi:10.1103/PhysRevB.81.054434.
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