Spin state of iron - controlling parameter of iron containing HTSC: dependence of ground state energy, phonon energies and positions of atoms on spin state of iron ion in FeTe
Yu.G. Pashkevich, T.N. Shevtsova, A.A. Gusev
O.O. Galkin Donetsk Institute for Physics and Technology, National Academy of Science of Ukraine 72 R. Luxemburg Str., Donetsk 83114, Ukraine
B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine, 47 Lenin Ave., Kharkov 61103, Ukraine
Institute for Condensed Matter Physics, TU Braunschweig, D-38106 Braunschweig, Germany pos Анотація:
Received May 18, 2012
The density functional theory is used to calculate electronic structure, ground state energy, phonon frequencies
at the center and at the boundary of the Brillouin zone, and distribution of magnetic moment over d-orbitals of iron are calculated as a function of magnetic moment — spin state of iron in the magnetically ordered phase of FeTe by using the density functional theory. It is shown that a ground state energy minimum is achieved at a certain d-orbital distribution of
magnetic moment and at a certain spin state of an iron ion. The impact of a new type of interaction (“the spin
state–lattice” one) on the phonon subsystem is studied numerically. It is found that a high-frequency part of the
phonon spectra undergoes the most significant changes with changing the spin state. To describe the properties
of the HTSC iron-containing compounds, an integral parameter (spin state of iron ion) is suggested.
PACS: 74.25.Kc Phonons; PACS: 74.70.–b Superconducting materials, other than cuprates; PACS: 63.20.D– Phonon states and bands, normalmodes, and phonon dispersion.
Key words: spin state, the ground state energy, electronic structure, phonons, spin-lattice interaction, the Mott transition.