F. Geist et al., MAGNETOOPTICAL INVESTIGATIONS OF EU-BASED DILUTED MAGNETIC LEAD CHALCOGENIDES, Physical review. B, Condensed matter, 56(20), 1997, pp. 13042-13053
MBE grown Pb1-xEuxTe and Pb1-xEuxSe films with Eu contents up to 7% we
re investigated by various magneto-optical methods as interband absorp
tion, photomodulated reflectivity, photoluminescence, and coherent ant
i-Stokes Raman scattering (CARS) in the midinfrared. The observed inte
rband and intraband transition energies were interpreted in the framew
ork of the Mitchell and Wallis band-structure model with the exchange
interaction taken into account in mean-field approximation. The interb
and matrix elements of the selenide are independent of the Eu concentr
ation up to x=0.07, whenas in the telluride they are reduced by about
a factor of 2 between x=0 and 0.05. The signs and the magnitudes of th
e exchange parameters for the exchange interaction between the free ca
rriers in the conduction and valence band, respectively, and the local
ized magnetic moments of the Eu2+ ions are similar in Pb1-xEuxTe and P
b1-xEuxSe. This implies that in Pb1-xEuxTe the exchange interaction de
creases the spin splitting of the valence band as it is known from Pb1
-xEuxSe. The sign and magnitude of the exchange parameters are differe
nt from the Mn-based compounds indicating that the effect is dominated
by the hybridization of the band states with the localized wave funct
ions of the 4f or 3d electrons, respectively. The minima of the magnet
oabsorption spectra exhibit a strong line broadening with increasing E
u concentration. Weaker transitions are no longer observable. Thus for
higher Eu contents CARS turned out to be important not only for the d
etermination of exchange parameters but also for the precise determina
tion of the anisotropy of the interband matrix elements. With increasi
ng x a strong decrease of the matrix elements is observed in the tellu
ride, whereas the matrix elements in the selenide are less influenced.