Covalency and the Paramagnetic Resonance ofMn++in CdSe

Abstract

The paramagnetic resonance spectrum of divalent manganese has been measured in a single crystal of CdSe (CV) at 77°K. The parameters are g=2.003±0.001, A = (-62.7±0.5)X10" 4 cm" 1 , D= (15.2±0.5) X10" 4 cm" 1 , a= (+!4.3±1.0)X10-4 cm" 1 , F= (-2.0±1.0)Xl(r 4 cm" 1 . It is to be noted that in this hexagonal crystal the effect of the cubic field parameter a is comparable to that of the axial field parameter D. The large value of a is attributed to covalency effects. A comparison of the measured a value with a values found for Mn++ in other wurtzite and zincblende crystals shows that there is a correlation between the magnitude of the a value and the amount of covalency. A similar correlation between the value of D and the amount of covalency is also found and accounts for the low value of D in CdSe.

Excitonic Zeeman splittings in colloidal CdSe quantum dots doped with single magnetic impurities

“…Six hyperfine lines of approximately equal intensity are observed, with a splitting of |A| = 62.1 × 10 -4 cm -1 , consistent with substitutional Mn 2+ in CdSe. 28 The narrow feature width and absence of broad underlying intensity are both consistent with negligible Mn 2+ -Mn 2+ dipolar coupling, as anticipated at this low doping concentration. Figure 2A shows the 1.7 K zero-field electronic absorption spectrum of the QDs from Excitonic Zeeman splittings (ΔE Z ) of the 1S 3/2 1S e exciton were calculated from the absorption and MCD data of Figure 2A,B using Equation 1, 12,18 where ΔA' corresponds to the maximum amplitude of the lowest-energy leading-edge MCD feature and A 0 and σ are the height and Gaussian width of the absorption peak, respectively, determined by multi-peak Gaussian fitting using fixed heights and widths across the magnetic field range, according to the rigid-shift approximation.…”

“…Six hyperfine lines of approximately equal intensity are observed, with a splitting of |A| = 62.1 × 10 -4 cm -1 , consistent with substitutional Mn 2+ in CdSe. 28 The narrow feature width and absence of broad underlying intensity are both consistent with negligible Mn 2+ -Mn 2+ dipolar coupling, as anticipated at this low doping concentration.…”

Mn2+‐Doped CdSe Quantum Dots: New Inorganic Materials for Spin‐Electronics and Spin‐Photonics

“…7) and the g, hyperfine (A), cubic field (a), and axial zero-field splitting (D and F) parameters deduced from EPR studies of oriented single crystals of wurtzite Mn 2þ :CdSe. [141] This axial hyperfine spectrum demonstrates Mn 2þ substitution at the axial cation site of the wurtzite CdSe lattice in these nanocrystals.…”

“…Bottom: Experimental and simulated 6.3(1) K X-band EPR spectra of colloidal d % 4.2 nm $0.1% Mn 2þ :CdSe nanocrystals suspended in toluene. The simulation was performed using the axial spin Hamiltonian of Equation 7 using the same parameters derived previously from fitting bulk Mn 2þ :CdSe EPR spectra [141]: g ¼ 2.0041, A ¼ À62.2 Â 10 À4 cm À1 , D ¼ 15.6 Â 10 À4 cm À1 , F ¼ À2.0 Â 10 À4 cm À1 , a ¼ 14.3 Â 10 À4 cm À1 . this synthetic route thus appears beneficial for doping, a conclusion reminiscent of the Kanatzidis group's success in preparing Cd 1-x Mn x Se (0 x 1) nanocrystalline powders at temperatures below 155 8C.…”

Correlation of Zero Field Splittings and Site Distortions V. Mn2+ in Cs2Zn3S4

“…They can be explained within the MO formalism as a result of covalent admixture of ligand /^-functions into the metal 3d functions which effectively results in transfer of negative charge from the ligands to the central ion [20,23]. Since this positive g-shift increases from sulfides to tellurides [17,24], it can be regarded as a rough measure of covalency. The values for Mn 2+ in Cs 2 Zn 3 S 4 are higher than in binary sulfides and in CdGa 2 S 4 .…”