Suchergebnisse

Single-crystal, microcrystalline and nanocrystalline nickel oxides (NiO) have been studied by Raman spectroscopy. A new band at ~200 cm-1 and TO-LO splitting of the band at 350–650 cm-1 have been found in the spectra of single-crystals NiO(100), NiO(110) and NiO(111). The Raman spectra of microcrystalline (1500 nm) and nanocrystalline (13–100 nm) NiO resemble those of the single crystals. They all contain the two-magnon band at 1500 cm-1, indicating that the oxides remain at room temperature in the antiferromagnetic phase. Besides, a new sharp Raman band has been observed at 500 cm-1 in nanocrystalline NiO. Its temperature dependence suggests the magnetic origin of the band, possibly associated with the one-phonon–one-magnon excitation at the Brillouin zone centre. ; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART²

This study was supported by a grant from Latvian Council of Science (agreement No. LZP-2018/1-0214). ; Original results on the EPR and photoluminescence Cr3+ ions in natural magnesium aluminum spinel (MgAl2O4) are presented. The photoluminescence spectra of Cr3+ ions in natural MgAl2O4 have been measured before and after irradiated by fast neutrons. --- / / / --- This is the preprint version of the following article: N. Mironova-Ulmane, A. I. Popov, G. Krieke, A. Antuzevics, V. Skvortsova, E. Elsts, and A. Sarakovskis, Low-temperature studies of Cr3+ ions in natural and neutron-irradiated Mg-Al spinel, Low Temperature Physics,46, 1154 (2020), DOI https://doi.org/10.1063/10.0002467, which has been published in final form at https://aip.scitation.org/doi/10.1063/10.0002467. This article may be used for non-commercial purposes in accordance with American Institute of Physics terms and conditions for Sharing and Self-Archiving. ; Latvian Council of Science (agreement No. LZP-2018/1-0214); Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART².

The present study has been supported by the Latvian National Research Program IMIS2. One of us, IS, was supported by MES RF RFMEFI61615X0064. ; X-ray diffraction, micro-Raman and the Fourier transform infrared spectroscopies as well as magnetometry measurements were performed on nanosized manganese oxides to probe their phase composition and magnetic properties. It was shown that the XRD method is less sensitive to phase composition of manganese oxide samples than spectroscopic methods. While in some samples the XRD method recognised only the manganosite MnO phase, the Raman and FT-IR methods revealed additionally the presence of the hausmannite Mn3O4 phase. ; Ministry of Education and Science RF RFMEFI61615X0064; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART²