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

Abstract

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 Mn 2+ 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 Mn 2+ concentration based on the spin− lattice relaxation dynamics of the Mn 2+ spin system.

Optically detected magnetic resonance in CdSe/CdMnS nanoplatelets

“…Previously, we examined the CdSe/(Cd,Mn)S NPLs considered here by means of several magneto-optical techniques. 22 We conclude that the photoluminescence is contributed by recombination of neutral (bright and dark) and charged excitons. The exchange interaction of neutral and charged excitons localized in the CdSe core with the magnetic Mn 2+ ions in the shell was demonstrated.…”

“…The polarization originates from the Zeeman splitting of the exciton states and reflects their different thermal populations. 38 The DCP for neutral and charged excitons (trions) can be written as 22,39,40…”

“…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.…”

“…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. 22 In this paper, we present optically detected magnetic resonance studies of core/shell CdSe/(Cd,Mn)S and CdSe/(Cd,Zn, Mn)S nanoplatelets. Resonant heating of the Mn spins by microwave radiation is detected.…”