Browsing by Author "Bayer, M."
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Item Open Access High-frequency EPR and ENDOR spectroscopy of Mn2+ ions in CdSe/CdMnS nanoplatelets(American Chemical Society, 2023-02-20) Babunts, Roman A.; Uspenskaya, Yulia A.; Romanov, Nikolai G.; Orlinskii, Sergei B.; Mamin, Georgy V.; Shornikova, Elena V.; Yakovlev, Dmitri R.; Bayer, M.; Işık, Furkan; Shendre, S.; Delikanlı, Savaş; Demir, Hilmi VolkanSemiconductor colloidal nanoplatelets based of CdSe have excellent optical properties. Their magneto-optical and spin-dependent properties can be greatly modified by implementing magnetic Mn2+ ions, using concepts well established for diluted magnetic semiconductors. A variety of magnetic resonance techniques based on high-frequency (94 GHz) electron paramagnetic resonance in continuous wave and pulsed mode were used to get detailed information on the spin structure and spin dynamics of Mn2+ ions in core/shell CdSe/(Cd,Mn)S nanoplatelets. We observed two sets of resonances assigned to the Mn2+ ions inside the shell and at the nanoplatelet surface. The surface Mn demonstrates a considerably longer spin dynamics than the inner Mn due to lower amount of surrounding Mn2+ ions. The interaction between surface Mn2+ ions and 1H nuclei belonging to oleic acid ligands is measured by means of electron nuclear double resonance. This allowed us to estimate the distances between the Mn2+ ions and 1H nuclei, which equal to 0.31 ± 0.04, 0.44 ± 0.09, and more than 0.53 nm. This study shows that the Mn2+ ions can serve as atomic-size probes for studying the ligand attachment to the nanoplatelet surface.Item Open Access Magneto-optics of excitons interacting with magnetic ions in CdSe/CdMnS colloidal nanoplatelets(American Chemical Society, 2020-06) Shornikova, E. V.; Yakovlev, D. R.; Tolmachev, D. O.; Ivanov, V. Y.; Kalitukha, I. V.; Sapega, V. F.; Kudlacik, D.; Kusrayev, Y. G.; Golovatenko, A. A.; Shendre, S.; Delikanlı, Savaş; Demir, Hilmi Volkan; Bayer, M.Excitons in diluted magnetic semiconductors represent excellent probes for studying the magnetic properties of these materials. Various magneto-optical effects, which depend sensitively on the exchange interaction of the excitons with the localized spins of the magnetic ions can be used for probing. Here, we study core/shell CdSe/(Cd,Mn)S colloidal nanoplatelets hosting diluted magnetic semiconductor layers. The inclusion of the magnetic Mn2+ ions is evidenced by three magneto-optical techniques using high magnetic fields up to 15 T: polarized photoluminescence, optically detected magnetic resonance, and spin-flip Raman scattering. We show that the holes in the excitons play the dominant role in exchange interaction with magnetic ions. We suggest and test an approach for evaluation of the Mn2+ concentration based on the spin− lattice relaxation dynamics of the Mn2+ spin system.Item Open Access Optically detected magnetic resonance in CdSe/CdMnS nanoplatelets(Royal Society of Chemistry, 2020) Tolmachev, D. O.; Ivanov, V. Y.; Yakovlev, D. R.; Shornikova, E. V.; Witkowski, B.; Shendre, S.; Işık, Furkan; Delikanlı, Savaş; Demir, Hilmi Volkan; Bayer, M.Core/shell CdSe/(Cd,Mn)S colloidal nanoplatelets containing magnetic Mn2+ ions are investigated by the optically detected magnetic resonance technique, combining 60 GHz microwave excitation and photoluminescence detection. Resonant heating of the Mn spin system is observed. We identify two mechanisms of optical detection, via variation of either the photoluminescence polarization or its intensity in an external magnetic field. The spin–lattice relaxation dynamics of the Mn spin system is measured and used for evaluation of the Mn concentration. In CdSe/(Cd,Zn,Mn)S nanoplatelets the addition of Zn in the shells significantly broadens the magnetic resonance, evidencing local strain.