02151nas a2200133   4500008004100000245015800041210006900199260000800268490000800276520156000284100002701844700001601871856013001887       2017                        eng d00aTuning of the magnetostrictive properties of cobalt ferrite by forced distribution of substituted divalent metal ions at different crystallographic sites0 aTuning of the magnetostrictive properties of cobalt ferrite by f  cMAR0 v1213 aComparative studies have been made to understand the role of different crystallographic site preferences of the substituted non-magnetic divalent metal ions in the magnetostrictive properties of cobalt ferrite, by substitution of Zn2+ and/or Mg2+ for Fe3+ in CoMgxFe2-xO4, CoZnxFe2-xO4, and CoMgx/2Znx/2Fe2-xO4 (0.0 <= x <= 0.2). Detailed Raman spectral and magnetic characterizations are made to extract the information on the tetrahedral/octahedral site preferences of Zn and Mg in the spinel lattice of cobalt ferrite. The structural, microstructural, magnetic, Raman spectral, and magnetostrictive parameters of the studied compositions show distinguishable variations for x< 0.1 and x >= 0.1. Co-substitution of a small amount of Mg and Zn for Fe in CoMgx/2Znx/2Fe2-xO4 (x < 0.1) showed relatively larger strain sensitivity, [d lambda/dH](max) (-2.6 x 10(-9) mA(-1) for x = 0.05), higher than that for the Mg-substituted samples (-2.05 x 10(-9) mA(-1) for x = 0.05) and comparable to that for the Zn-substituted samples (-2.47 x 10(-9) mA(-1) for x = 0.05), without much drop in the maximum value of magnetostriction, lambda(max) (-189 ppm for x = 0.05) compared to that for the unsubstituted counterpart (-221 ppm). The results show that it is possible to obtain high strain sensitivity (at fields < 50 kA/m), along with high magnetostriction strain at low magnetic fields (similar to 250 kA/m), by tuning the distribution of the substituted cations in the tetrahedral and octahedral sites of the cobalt ferrite lattice. Published by AIP Publishing.1 aAnantharamaiah, P., N.1 aJoy, P., A.  uhttps://library.ncl.res.in/content/tuning-magnetostrictive-properties-cobalt-ferrite-forced-distribution-substituted-divalent01713nas a2200157   4500008004100000022001500041245011900056210006900175260000800244490000700252520112200259100001401381700001501395700001601410856012901426       2018                        eng d  a 0250-470700aThermal conductivity studies on magnetite nanofluids coated with short-chain and long-chain fatty acid surfactants0 aThermal conductivity studies on magnetite nanofluids coated with  cOCT0 v413 aThe effect of the length of surfactant molecules on the surface of the nanoparticles on the thermal conductivity of nanofluids is studied. Magnetite (Fe3O4) nanoparticles of comparable sizes are stabilized with short-chain capric acid (C9H19COOH) and long-chain stearic acid (C17H35COOH) molecules. Thermal conductivity of the two surfactant-coated magnetite nanoparticles dispersed in toluene is measured as a function of the concentration of the particles in the fluids and in the presence of a magnetic field. Studies showed that the critical concentration for thermal conductivity enhancement is lower for stearic-acid-coated fluid as compared with the capric-acid-coated fluid. Comparable enhancement in the thermal conductivity is observed at higher concentrations of the particles. Relatively larger enhancement in the thermal conductivity is observed for the capric-acid-coated fluid in a magnetic field. The difference in the enhancement in the thermal conductivity, depending on the chain length of the surfactant, is explained in terms of the inter-particle magnetic interactions and formation of clusters.1 aLenin, R.1 aDadwal, A.1 aJoy, P., A.  uhttps://library.ncl.res.in/content/thermal-conductivity-studies-magnetite-nanofluids-coated-short-chain-and-long-chain-fatty