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Tatsumi K, Inamura Y, Kofu M, Kiyanagi R, Shimazaki H. Optimization and inference of bin widths for histogramming inelastic neutron scattering spectra. J Appl Crystallogr 2022; 55:533-543. [PMID: 35719304 PMCID: PMC9172031 DOI: 10.1107/s1600576722003624] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Accepted: 03/30/2022] [Indexed: 11/23/2022] Open
Abstract
A data-driven bin-width optimization for the histograms of measured data sets based on inhomogeneous Poisson processes was developed in a neurophysiology study [Shimazaki & Shinomoto (2007). Neural Comput. 19, 1503-1527], and a subsequent study [Muto, Sakamoto, Matsuura, Arima & Okada (2019). J. Phys. Soc. Jpn, 88, 044002] proposed its application to inelastic neutron scattering (INS) data. In the present study, the results of the method on experimental INS time-of-flight data collected under different measurement conditions from a copper single crystal are validated. The extrapolation of the statistics on a given data set to other data sets with different total counts precisely infers the optimal bin widths on the latter. The histograms with the optimized bin widths statistically verify two fine-spectral-feature examples in the energy and momentum transfer cross sections: (i) the existence of phonon band gaps; and (ii) the number of plural phonon branches located close to each other. This indicates that the applied method helps in the efficient and rigorous observation of spectral structures important in physics and materials science like novel forms of magnetic excitation and phonon states correlated to thermal conductivities.
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Affiliation(s)
- Kazuyoshi Tatsumi
- Materials and Life Science Division, J-PARC Center, Japan Atomic Energy Agency, Shirakata 2-4, Tokai, Ibaraki 319-1195, Japan
| | - Yasuhiro Inamura
- Materials and Life Science Division, J-PARC Center, Japan Atomic Energy Agency, Shirakata 2-4, Tokai, Ibaraki 319-1195, Japan
| | - Maiko Kofu
- Materials and Life Science Division, J-PARC Center, Japan Atomic Energy Agency, Shirakata 2-4, Tokai, Ibaraki 319-1195, Japan
| | - Ryoji Kiyanagi
- Materials and Life Science Division, J-PARC Center, Japan Atomic Energy Agency, Shirakata 2-4, Tokai, Ibaraki 319-1195, Japan
| | - Hideaki Shimazaki
- Center for Human Nature, Artificial Intelligence and Neuroscience, Hokkaido University, Kita-ku, Sapporo, Hokkaido 060-0812, Japan
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Gudkov VV, Sarychev MN, Zherlitsyn S, Zhevstovskikh IV, Averkiev NS, Vinnik DA, Gudkova SA, Niewa R, Dressel M, Alyabyeva LN, Gorshunov BP, Bersuker IB. Sub-lattice of Jahn-Teller centers in hexaferrite crystal. Sci Rep 2020; 10:7076. [PMID: 32341430 PMCID: PMC7184747 DOI: 10.1038/s41598-020-63915-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Accepted: 04/01/2020] [Indexed: 11/09/2022] Open
Abstract
A novel type of sub-lattice of the Jahn-Teller (JT) centers was arranged in Ti-doped barium hexaferrite BaFe12O19. In the un-doped crystal all iron ions, sitting in five different crystallographic positions, are Fe3+ 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 Fe2+ predominantly in tetrahedral coordination, resulting in doubly-degenerate states subject to the [Formula: see text] problem of the JT effect. The arranged JT complexes, Fe2+O4, 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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Affiliation(s)
- V V Gudkov
- Institute of Physics and Technology, Ural Federal University, Ekaterinburg, Russia.,South Ural State University, Chelyabinsk, Russia
| | - M N Sarychev
- Institute of Physics and Technology, Ural Federal University, Ekaterinburg, Russia
| | - S Zherlitsyn
- Hochfeld-Magnetlabor Dresden (HLD-EMFL), Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
| | - I V Zhevstovskikh
- Institute of Physics and Technology, Ural Federal University, Ekaterinburg, Russia.,M.N. Miheev Institute of Metal Physics, UB of the RAS, Ekaterinburg, Russia
| | - N S Averkiev
- A.F. Ioffe Physical Technical Institute of the RAS, St. Petersburg, Russia
| | - D A Vinnik
- South Ural State University, Chelyabinsk, Russia
| | - S A Gudkova
- South Ural State University, Chelyabinsk, Russia.,Moscow Institute of Physics and Technology (State University), Dolgoprudny, Russia
| | - R Niewa
- Institute of Inorganic Chemistry, University of Stuttgart, Stuttgart, Germany
| | - M Dressel
- Moscow Institute of Physics and Technology (State University), Dolgoprudny, Russia.,1. Physikalisches Institut, Universität Stuttgart, Stuttgart, Germany
| | - L N Alyabyeva
- Moscow Institute of Physics and Technology (State University), Dolgoprudny, Russia.
| | - B P Gorshunov
- Moscow Institute of Physics and Technology (State University), Dolgoprudny, Russia
| | - I B Bersuker
- Institute for Theoretical Chemistry, the University of Texas at Austin, Austin, TX, USA
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Tuning the Electrical and Thermoelectric Properties of N Ion Implanted SrTiO 3 Thin Films and Their Conduction Mechanisms. Sci Rep 2019; 9:14486. [PMID: 31597931 PMCID: PMC6785559 DOI: 10.1038/s41598-019-51079-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2019] [Accepted: 09/11/2019] [Indexed: 11/30/2022] Open
Abstract
The SrTiO3 thin films were fabricated by pulsed laser deposition. Subsequently ion implantation with 60 keV N ions at two different fluences 1 × 1016 and 5 × 1016 ions/cm2 and followed by annealing was carried out. Thin films were then characterized for electronic structure, morphology and transport properties. X-ray absorption spectroscopy reveals the local distortion of TiO6 octahedra and introduction of oxygen vacancies due to N implantation. The electrical and thermoelectric properties of these films were measured as a function of temperature to understand the conduction and scattering mechanisms. It is observed that the electrical conductivity and Seebeck coefficient (S) of these films are significantly enhanced for higher N ion fluence. The temperature dependent electrical resistivity has been analysed in the temperature range of 80–400 K, using various conduction mechanisms and fitted with band conduction, near neighbour hopping (NNH) and variable range hopping (VRH) models. It is revealed that the band conduction mechanism dominates at high temperature regime and in low temperature regime, there is a crossover between NNH and VRH. The S has been analysed using the relaxation time approximation model and dispersive transport mechanism in the temperature range of 300–400 K. Due to improvement in electrical conductivity and thermopower, the power factor is enhanced to 15 µWm−1 K−2 at 400 K at the higher ion fluence which is in the order of ten times higher as compared to the pristine films. This study suggests that ion beam can be used as an effective technique to selectively alter the electrical transport properties of oxide thermoelectric materials.
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