The formation of local moments and the effect of charge carriers in dilute magnetic semiconductors can be well understood using local probe techniques like Mossbauer Spectroscopy. We report here on Mossbauer studies in the systems Fe 0.008 Ge 1jx D x (D = As, Bi), Fe 0.008 Ge 1jx In x , and Fe 0.008 Ge 1 j x Sn x . At room temperature magnetic interactions were observed for donor (D) impurities at the Fe site in the Fe 0.008 Ge system. No such magnetic ordering was observed for acceptor (In) or neutral (Sn) impurities.

High-energy MeV ions from accelerators are known to produce drastic modifications in polymers. The typical effects include chain scissions, crosslinks, molecular emission and double bond formation. Poly(methyl methacrylate) was doped with Fe(III) and irradiated with 95 MeV O 7+ ions. 57 Fe-Mössbauer studies were done on the doped samples before and after irradiation. Before irradiation, no Mössbauer absorption was observed. The irradiated samples showed a good Mössbauer absorption, which seems to indicate that there is a significant interaction between the metal ion and the polymer matrix. Two possibilities exist at these doses (~ 22 × 10 12 ions/cm): Fe(III) ions may be bridging the various polymer segments through crosslinking or amorphization of the sample leading to Fe-C bonding. Studies of FTIR, conductivity and glass transition temperatures on these samples support these observations.

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A dilute quantity of Fe (0.008) was doped into V-VI (Sb1−xSex) for X=0 to 0.50 alloys based on Sb semimetal. Hall measurements showed that the materials were n-type semiconductors for X=0.01 to 0.10 and the charge carrier densities increased from 4.2×1019cm−3 to 1.142×1021cm−3 in this region. For higher concentration of Se (X=0.50), the charge carrier densities decreased dramatically to 2.1×1015. For X=0, Fe showed no magnetic moment. For X=0.01 to 0.1 two magnetic sites (A and B) were observed at room temperature by Mossbauer measurement. Site A appears to be an SeFeSb, type ternary alloy. p-d interaction and carrier-induced polarization seem to be responsible for the magnetic interaction at this site (A). Tc (for Site A) was measured to be ∼573K. Similar behavior was observed for Fe(0.002). Site B Mossbauer parameters coincide with those of Fe7Se8.

Hyperfine interaction techniques like Mossbauer spectroscopy are very sensitive tools to study the local probe interactions in dilute magnetic semiconductors. We report here a Mossbauer study on the concentration dependence in Fe 0.008 Ge 1 j x Te x for x = 0, 0.008, 0.016, 0.03 and 0.05. At room temperature magnetic interactions were observed for all concentrations of Te and the population of magnetic site was found to increase gradually with the Te concentration. A constant magnetic hyperfine field of 136 KOe was found. A quadrupole doublet due to the FeTe 2 compound phase was also seen.

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