Showing papers by "Harish Verma published in 2000"
TL;DR: In this paper, the as-prepared sample was largely ferrimagnetic and, as the sample was annealed at temperatures above 250 °C, it gradually became superparamagnetic.
Abstract: Nanosize particles (average size ∼12 nm) of mixed ferrite Mn0.65Zn0.35Fe2O4 were prepared by the hydrothermal precipitation route and studied using x-ray diffraction, transmission electron microscopy, differential scanning calorimetry, magnetization measurements, and Mossbauer spectroscopy. The as-prepared sample was largely ferrimagnetic and, as the sample was annealed at temperatures above 250 °C, it gradually became superparamagnetic. This unexpected behavior is explained by assuming that the cation distribution in the nanosize as-prepared sample is in a metastable state and, as the sample is heated, this distribution changes to a more stable state while the grain size remains nearly the same.
75 citations
TL;DR: The Didwana-Rajod chondrite's iron phases and its oxidation states strongly suggest that it should be classified as an H-type ordinary chondite instead of the earlier suggestion (based on petrographic studies) that it could be an enstatite chondlite.
Abstract: — Mossbauer spectroscopic studies of the Didwana-Rajod chondrite, which fell on 1991 August 12 in western Rajasthan, India, are presented. The results are compared with the Mossbauer data of several enstatite and ordinary chondrites including the Dhajala chondrite for which Mossbauer data were acquired during the present study. The Didwana-Rajod chondrite's iron phases and its oxidation states strongly suggest that it should be classified as an H-type ordinary chondrite instead of the earlier suggestion (based on petrographic studies) that it could be an enstatite chondrite. The present study demonstrates that Mossbauer spectroscopy is a very powerful technique for aiding in the classification of meteorites.
27 citations
TL;DR: In this article, the results of Mossbauer spectroscopic investigations of two meteorites belonging to the howardite-eucrite-diogenite (HED) group are presented.
Abstract: — Two meteorites belonging to the howardite-eucrite-diogenite (HED) group fell recently in Rajasthan, India. One of these, Piplia Kalan, was classified as a eucrite and the other, Lohawat, as a howardite. In this study, we present the results of Mossbauer spectroscopic investigations of these two meteorites. We also compare the results with the Mossbauer experiments reported for the Kapoeta howardite and look for systematics in the Mossbauer spectra of HED meteorites.
12 citations
TL;DR: In this paper, it is suggested that a fraction of iron ions migrated from the A-sublattice to the B-sub-lattices due to vacancy creation and rearrangement during filing, and it remains there even after prolonged heating.
8 citations