A novel type of sub-lattice of the Jahn-Teller (JT) centers was arranged in Ti-doped barium hexaferrite BaFeO. In the un-doped crystal all iron ions, sitting in five different crystallographic positions, are Fe in the high-spin configuration (S = 5/2) and have a non-degenerate ground state. We show that the electron-donor Ti substitution converts the ions to Fe predominantly in tetrahedral coordination, resulting in doubly-degenerate states subject to the [Formula: see text] problem of the JT effect. The arranged JT complexes, FeO, their adiabatic potential energy, non-linear and quantum dynamics, have been studied by means of ultrasound and terahertz-infrared spectroscopies. The JT complexes are sensitive to external stress and applied magnetic field. For that reason, the properties of the doped crystal can be controlled by the amount and state of the JT complexes.
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http://dx.doi.org/10.1038/s41598-020-63915-7 | DOI Listing |
J Phys Condens Matter
September 2022
Prokhorov General Physics Institute of the Russian Academy of Sciences, Vavilov str. 38, Moscow 119991, Russia.
TmYbBdodecaborides represent model objects for the studies of quantum critical behavior, metal-insulator transitions (MITs) and complex charge-spin-orbital-phonon coupling phenomena. In spite of intensive investigations, the mechanism of semiconducting ground state formation both in YbBand in the Yb-based strongly correlated electron systems remains a subject of active debates. We have performed first systematic measurements of temperature-dependent spectra of infrared conductivity of TmYbBat frequencies 40-35 000 cmand in the temperature range 10-300 K.
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April 2020
Institute for Theoretical Chemistry, the University of Texas at Austin, Austin, TX, USA.
A novel type of sub-lattice of the Jahn-Teller (JT) centers was arranged in Ti-doped barium hexaferrite BaFeO. In the un-doped crystal all iron ions, sitting in five different crystallographic positions, are Fe in the high-spin configuration (S = 5/2) and have a non-degenerate ground state. We show that the electron-donor Ti substitution converts the ions to Fe predominantly in tetrahedral coordination, resulting in doubly-degenerate states subject to the [Formula: see text] problem of the JT effect.
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January 2018
School of Physical Sciences, Ingram Building, University of Kent, Canterbury, CT2 7NH, United Kingdom.
Copper ferrite, belonging to the wide and technologically relevant class of spinel ferrites, was grown in the form of t-CuFeO nanocrystals within a porous matrix of silica in the form of either an aerogel or a xerogel, and compared to a bulk sample. Extended X-ray absorption fine structure (EXAFS) spectroscopy revealed the presence of two different sub-lattices within the crystal structure of t-CuFeO, one tetragonal and one cubic, defined by the Cu and Fe ions respectively. Our investigation provides evidence that the Jahn-Teller distortion, which occurs on the Cu ions located in octahedral sites, does not affect the coordination geometry of the Fe ions, regardless of their location in octahedral or tetrahedral sites.
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