New Samarium and Neodymium based admixed ferromagnets with near zero net magnetization and tunable exchange bias field

Rare earth based intermetallics, SmScGe and NdScGe, are shown to exhibit near zero net magnetization with substitutions of 6 to 9 atomic percent of Nd and 25 atomic percent of Gd, respectively. The notion of magnetic compensation in them is also elucidated by the crossover of zero magnetization axis at low magnetic fields (less than 103 Oe) and field-induced reversal in the orientation of the magnetic moments of the dissimilar rare earth ions at higher magnetic fields. These magnetically ordered materials with no net magnetization and appreciable conduction electron polarization display an attribute of an exchange bias field, which can be tuned. The attractively high magnetic ordering temperatures of about 270 K, underscore the importance of these materials for potential applications in spintronics.Comment: 6 page text + 5 figure

Hydrothermal Synthesis, Microstructure and Photoluminescence of Eu3+-Doped Mixed Rare Earth Nano-Orthophosphates

Eu3+-doped mixed rare earth orthophosphates (rare earth = La, Y, Gd) have been prepared by hydrothermal technology, whose crystal phase and microstructure both vary with the molar ratio of the mixed rare earth ions. For LaxY1–xPO4: Eu3+, the ion radius distinction between the La3+ and Y3+ is so large that only La0.9Y0.1PO4: Eu3+ shows the pure monoclinic phase. For LaxGd1–xPO4: Eu3+ system, with the increase in the La content, the crystal phase structure of the product changes from the hexagonal phase to the monoclinic phase and the microstructure of them changes from the nanorods to nanowires. Similarly, YxGd1–xPO4: Eu3+, Y0.1Gd0.9PO4: Eu3+ and Y0.5Gd0.5PO4: Eu3+ samples present the pure hexagonal phase and nanorods microstructure, while Y0.9Gd0.1PO4: Eu3+ exhibits the tetragonal phase and nanocubic micromorphology. The photoluminescence behaviors of Eu3+ in these hosts are strongly related to the nature of the host (composition, crystal phase and microstructure)

Segregation behaviour of trace metal impurities during ultra high purification of gallium by zone refining

783-786The details of an in-house fabricated laboratory scale horizontal zone-refiner (HZR) for the purification of indigenous 4N (99.99%) gallium have been reported. The purified gallium ingot was analyzed for its selected trace metal impurity elements, namely Zn, Pb, Cu, AI, Cr, Ni, Fe, B and Mn using inductively coupled plasma optical emission spectrophotometer (ICP-OES). Segregation behaviour of the trace metal impurities throughout the ingot have been illustrated. The repeated experimental results confirm 6N (99.9999%) purity gallium. </span

Recovery of economic minerals from the Carbonatite-Sevattur (Tamil Nadu)

Carbonatites from Sevattur contain pyrochlore and apatite with calcite as the main gangue. The feed sample assayed 0.5% (NbTa)2O5 and 10.0% P2O5. The pyrochlore (uraniferous type) is in metamic state and is disseminated. Mineralogy was studied. Based on bench scale beneficiation tests conducted on batches of 19 to 100 kg, a flowsheet was proposed for the recovery of Nb-Ta concentrates (pyrochlore) and acid grade phosphate (apatite) from this carbonatite. The low concentration of pyrochlore [0.5% (NbTa)2O5)] in feed necessitated upgradation in stages to at least 60 times the feed value. Ore was ground to -48 mesh (wt% 98) and wet tablet. Table tails were scavenged in flotation circuit depressing pyrochlore with sodium silicate. The floats (calcite-apatite) were set apart for apatite recovery by calcination method. The cell products together with the table concentrates were subjected to magnetic separation. The non-magnetics were further recleaned and refined employing wet tabling followed by reverse flotation of pyrochlore (after sulphuric acid treatment). The recoveries obtained so far are (NaTa)2O5 (pyrochlore recovery 20% at 30% grade, P2O5 (apatite) recovery 50% at 35.2% grade. (Ch. Rambabu, J.B. Narasimhan, G.V.U. Rao and K.K. Majumdar, Ore Dressing Division, BARC, Bombay