D. Bahadur

Electron transport in hot pressed Y3−x Gd x Fe5O12

Electron transport properties of a few hot-pressed garnets of the series Y3−xGdxFe5O12 (wherex=0, 1 and 2·4) have been measured. For comparison, a normal sintered YIG has been studied to see the effect of porosity and microstructure. The electron transport properties have been discussed on the basis of the model suggested by Austin and Mott keeping in view the distortion caused by the substitution.

A ferromagnetic resonance study of as-quenched and annealed amorphous Fe78Cr2B12Si8

Ferromagnetic resonance (FMR) studies of as-quenched and annealed amorphous Fe78Cr2B12Si8 are presented. For short annealing times (∼30 min) and low annealing temperatures (473 K) the resonant field,H1, and the FMR line width, ΔH, are essentially constant. This can be explained in terms of a combination of effects due to magnetic anisotropy and the in homogeneous demagnetization due to stress relief in the sample. For larger annealing times or higher annealing temperatures,H1 and ΔH increase due to the percipitation of crystallites in the amorphous structure. X-ray diffraction, selected area electron diffraction patterns and transmission electron micrographs are consistent with this interpretation.

Spin-state equilibria in YbCoO3

The relative properties of high spin and low spin Co8+ in HoCoO3, ErCoO3 and LuCoO3 are about 1 : 1 above a characteristic temperature. YbCoO3 seems to show a similar behaviour with no evidence of electron transfer between the high spin and low spin states.

Electron transport in non-crystalline garnet films

Thin films of yttrium iron garnet (yig) and Gd-substitutedyig of different thickness have been prepared by flash evaporation. The surfacedc andac electrical resistivity and thermopower in these films have been studied. The results are explained on the basis of Mott and Davis model in which narrow tails of localised states exist at the extreme valence and conduction bands and a band of localised levels near the middle of the gap. For the temperature range studied, the main conduction mechanism is on account of excitation of carriers into localised states at the band edges and hopping at energies close to the band tails.

Characterization of RF-sputtered garnet films

Noncrystalline garnet films of nominal composition Y3Fe5O12 and Y2GdFe5O12 were synthesized by RF sputtering. The AC and DC resistivity data have been discussed in line with the model of Mott and Davis where conduction occurs through excitation of carriers into localized states at the band edges and hopping at energies close to the band tails.