Abstract
The magnetic susceptibility of Pb1-xCexA (A = S, Se and Te) crystals with 0.006 ≤ x ≤ 0.036 were studied in the temperature range from 20 mK up to room temperature. X-band (~9.5 GHz) Electron Paramagnetic Resonance (EPR) showed small shifts in the effective Landé factors that were attributed to crystal-field admixture. The EPR measurements were correlated with the magnetic susceptibility data and resulted in estimating the crystal-field splitting Δ = E(Γ8) - E(Γ7) of the lowest 2F5/2 manifold for Ce3+ ions in PbA (A = S, Se and Te) of about 340 K, 440 K and 540 K for Pb1-xCexTe, Pb1-xCexSe, and Pb1-xCexS, respectively. The values for the crystal-field splitting deduced from the magnetic data were found to be in agreement with the calculated ones based on the point charge model. Moreover, the deHaas van-Alphen magnetic oscillations in the susceptibility measurements of Pb1-xCexTe (x~ 0.05 and 0.07) were observed at ultra-low temperature (20 mK); The oscillations were investigated and the values of the oscillatory period for Pb1-xCexTe (x = 0.0048 and 0.007) are reported.
Highlights
Lead salts PbS, PbSe, and PbTe establish an significant group of Diluted magnetic semiconductors (DMS) consisting of a magnetic semiconducting host, in which fraction of cations is substituted by magnetic rare-earth or transition metal ions
The fcc structure of the samples were checked by X-Ray diffraction and the cerium content were determined from the magnetization saturation at high external magnetic field; the calculation of the Ce concentration (x) in the sample were corrected for the lattice diamagnetism ( D = -3.77×10-9 m3/Kg for PbS [19], D = -4.52×10-9 m3/Kg for PbSe [20], and D = -3.77×10-9 m3/Kg for PbTe [17]); The obtained average concentrations of cerium atoms were checked by Microprobe measurements, as given in Table I; An excellent agreement between the Ce concentrations values by microprobe to those obtained from magnetic measurements indicated that cerium is present only in its trivalent (Ce3+) state in our Pb1−xCexA samples
The temperature variation of for our Pb1xCexA (A = S, Se and Te) samples were found to strongly deviates from the free Ce ion paramagnetic behavior; it was noticed that the experimental magnetic susceptibility fits the predicted values of the susceptibility for the doublet ( 7) only at temperatures below 30 K indicating that the Kramer doublet ( 7) lies below the quadruplet ( 8)
Summary
Lead salts PbS, PbSe, and PbTe establish an significant group of Diluted magnetic semiconductors (DMS) consisting of a magnetic semiconducting host, in which fraction of cations is substituted by magnetic rare-earth or transition metal ions. The study of IV-VI DMS containing a fraction of non S-state rare-earth ions is much less explored [14,15,16]. For this class of DMS, the magnetic properties could be strongly affected by the presence of crystal-field splitting of the rare-earth states. The present data were used to estimate the cubic crystal-field splitting of the 2F5/2 manifold of Ce3+ in the three compounds
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