Narendra Patel

Mössbauer studies of iron doped poly(methyl methacrylate) before and after ion beam modification

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 O7+ ions.57Fe-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 × 1012 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.

Magnetic hyperfine fields in the room-temperature dilute magnetic semiconducting alloy Fe:Sb1−xSex

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.

Mössbauer Study of Multiple Substitutions in YBCO

Mössbauer studies of multiple substitutions in YBCO with general formula (Y1−ZCaZ)Ba2(Cu1−X−YFeYMX)3O7−δ are reported. XRD has been used to find out the lattice parameters. All the samples show a single tetragonal phase formation. Iodometric titration is done to estimate the oxygen content. The present study discusses the effect of multiple substitutions of 3d-ions like Ni, Zn, Co, Mn, Cr in YBCO and the effect of various substitutions on charge balancing, oxygen content and site occupancy.

Mössbauer Study of Magnetic FeSb Dilute System

Mössbauer study of semimetals is of great importance in understanding the origin of hyperfine interactions in these materials. A concentration dependence study in FexSb1−x for x=0.0025, 0.005, 0.01, 0.05, 0.10 and 0.20 is reported. It was found that for 0.0025<x<0.1 FeSb2 compound formation is inevitable. For x=0.0025 a magnetic interaction is observed along with a Quadrupole doublet whose value corresponds to the FeSb2 compound phase.

Perturbed angular correlation study of radiation-induced defects in Rh metal

Radiation-induced defects are studied in cubic rhodium metal, using the local probe technique ‘Time differential perturbed angular correlation’ (TDPAC) at liquid N2 temperature. Isochronal annealing was done at 300, 1073 and 1473 K temperatures. The irradiated sample showed two quadrupole interaction frequencies at 1150 and 93 MHz. The low frequency disappeared at room-temperature annealing, which was assigned to In trapped at a vacancy, whereas the higher frequency remained up to high temperatures and was attributed to In trapped at Rh–C complexes in the Rh matrix.