Persuasive Evidence for Electron–Nuclear Coupling in Diluted Magnetic Colloidal Nanoplatelets Using Optically Detected Magnetic Resonance Spectroscopy

Abstract

The incorporation of magnetic impurities into semiconductor nanocrystals with size confinement promotes enhanced spin exchange interaction between photogenerated carriers and the guest spins. This interaction stimulates new magnetooptical properties with significant advantages for emerging spin-based technologies. Here we observe and elaborate on carrier−guest interactions in magnetically doped colloidal nanoplatelets with the chemical formula CdSe/Cd 1−x Mn x S, explored by optically detected magnetic resonance and magneto-photoluminescence spectroscopy. The host matrix, with a quasi-type II electronic configuration, introduces a dominant interaction between a photogenerated electron and a magnetic dopant. Furthermore, the data convincingly presents the interaction between an electron and nuclear spins of the doped ions located at neighboring surroundings, with consequent influence on the carrier's spin relaxation time. The nuclear spin contribution by the magnetic dopants in colloidal nanoplatelets is considered here for the first time.

Optically detected magnetic resonance in CdSe/CdMnS nanoplatelets

“…Literature values of A are in the range from 6.65 to 7.17 mT. 20,[47][48][49] We choose A = 6.9 mT and D = 0, fit ODMR resonances in polarization from Fig. 3b and evaluate the width of individual spin levels, Γ.…”

“…Doping with magnetic ions has been successfully realized for colloidal NCs, where the characteristic DMS properties have been observed for spherical quantum dots (QDs), [8][9][10][11][12][13][14] nanoribbons, 15,16 and NPLs. [17][18][19][20][21][22] Optically detected magnetic resonance (ODMR) is a powerful technique for investigating the electronic and spin struc-ture of semiconductors and their nanostructures, for a review see ref. [24][25][26].…”

“…Also the spin-lattice relaxation (SLR) dynamics of the Mn spin system can be measured via time-resolved PL detection after pulsed microwave excitation. Very recently, ODMR studies of DMS CdSe/(Cd,Mn)S core/shell nanoplatelets 20,22 and nanorods 23 have been reported. The measured dynamics of the ODMR signals has been related to the spin-lattice relaxation dynamics of the Mn 2+ spin system and it has been suggested for evaluation of the Mn concentration.…”

Magneto-Optics of Excitons Interacting with Magnetic Ions in CdSe/CdMnS Colloidal Nanoplatelets

“…13−18 The exchange interaction of excitons with Mn 2+ ions was proven by optically detected magnetic resonance (ODMR). 19 Magnetic polaron formation was reported, 3,20−22 and the influence of Mn 2+ spin fluctuations was considered. 23 Magneto-optical studies of the exciton emission, its giant Zeeman splitting and polarization, are a valuable tool for investigation of DMS nanostructures.…”

Core‐crown Quantum Nanoplatelets with Favorable Type‐II Heterojunctions Boost Charge Separation and Photocatalytic NO Oxidation on TiO2

“…[70] Since the typical life times of such electron trapping events are rather short (in the order of 10 À 9 -10 À 3 s [71,72] ), long-life time (10 1 -10 2 s) radical spin traps such as 2,2,6,6-tetramethylpiperidin-1-yl) oxidanyl (TEMPO) or 5,5dimethyl-pyrroline N-oxide (DMPO) or metal cation dopants such as Mn 2 + were externally added to the analyzed samples to allow longer data acquisition times with a higher signal to noise ratio (S/N). [73][74][75] In the current in-situ X-band EPR measurements, no external spin-trap agents were added to the measured samples. Figure 6 reveals no detectable EPR signals for CdSe/ CdSeTe NPL in dark.…”