Influence ofs,p-dands−pexchange couplings on exc

Abstract

This work presents results of near-band gap magnetooptical studies on Zn 1−x Mn x O epitaxial layers. We observe excitonic transitions in reflectivity and photoluminescence that shift toward higher energies when the Mn concentration increases and split nonlinearly under the magnetic field. Excitonic shifts are determined by the s,p−d exchange coupling to magnetic ions, by the electron-hole s−p exchange, and the spin-orbit interactions. A quantitative description of the magnetoreflectivity findings indicates that the free excitons A and B are associated with the 7 and 9 valence bands, respectively, the order reversed as compared to wurtzite GaN. Furthermore, our results show that the magnitude of the giant exciton splittings, specific to dilute magnetic semiconductors, is unusual: the magnetoreflectivity data are described by an effective exchange energy N 0 (β (app) − α (app) ) = +0.2 ± 0.1 eV, which points to small and positive N 0 β (app) . It is shown that both the increase of the gap with x and the small positive value of the exchange energy N 0 β (app) corroborate recent theory describing the exchange splitting of the valence band in a nonperturbative way, suitable for the case of a strong p−d hybridization.

Fe dopant in ZnO: 2+ versus 3+ valency and ion-carrier s,p−d exchange interaction

“…Similar as in the study of (Zn,Mn)O (Ref. [9]), this effect can be explained in terms of spin-dependent exciton formation involving free and bound exciton states, as well as A and B excitons relaxation involving change of the exciton symmetry. For pure ZnO, the intensity of the excitonic PL linearly increases for σ+ and decreases for σ− in the magnetic field (not shown) due to polarization of the carriers induced by the Zeeman splitting of bands.…”

“…The obtained N 0 β, 0.5−1 eV, is smaller than typical ironhole exchange integrals for II-VI compounds, [75][76][77][78] but of the same order as effective exchange integrals reported for wide gap DMSs 8,9,[79][80][81][82][83] With the increasing U (Fe), t 2↑ approaches the valence band (see Fig. 2), which increases the spin splitting of the VBM, and for the U (Fe)= 4 eV the N 0 β reaches 2.0 eV .…”

Exchange integrals in Mn- and Co-doped II-VI semiconductors

“…This connects our consideration of the superexchange with the ligand field theory, where p-d hybridization appears in second order virtual hopping [25][26][27]. Moreover, the quantitative agreement of our model allows us to use the measurement of J dd to determine the p-d hybridization in addition or replacement of J sp−d [28].…”

Ultrafast spin dynamics in magnetic wide‐bandgap semiconductors

“…These relatively low values for N 0 α in Zn 1− x Mn x O might be explained by localization of holes at the Mn 2+ ions , i.e., we measure an apparent value for N 0 α with TRFR.…”