01955nas a2200157   4500008004100000022001400041245011900055210006900174260000800243300001400251490000700265520135300272100002701625700001601652856012901668       2015                        eng d  a0022-246100aMagnetic and magnetostrictive properties of aluminium substituted cobalt ferrite synthesized by citrate-gel method0 aMagnetic and magnetostrictive properties of aluminium substitute  cOCT  a6510-65170 v503 a<p>Structural, magnetic and magnetostrictive properties of sintered aluminium-substituted cobalt ferrite, CoAlxFe2-xO4 (x = 0.0, 0.1, 0.20, 0.30), derived from nanosized powders synthesized by a citrate-gel method, have been investigated. The sample with x = 0.1 is found to exhibit higher maximum magnetostriction strain at relatively lower magnetic fields (230 ppm at 286 kA/m) than that obtained for the unsubstituted cobalt ferrite (217 ppm, at 446 kA/m). All the Al-substituted compositions show larger strain sensitivity (d lambda/dH) at low magnetic fields compared to that for the unsubstituted cobalt ferrite. The variation of the magnetostriction coefficient as well as the strain sensitivity with Al content is likely to be due to the changes in the cation distribution in the tetrahedral and octahedral sites of the spinel lattice along with the associated changes in the magnetocrystalline anisotropy. The magnetostriction coefficient of x = 0.1 could be further enhanced to 306 ppm (at 220 kA/m) after a magnetic field annealing at 300 degrees C. A very high strain sensitivity of 4.5 x 10(-9) m/A is obtained for the magnetically annealed sample, larger than that reported for any substituted cobalt ferrite samples. The combination of high magnetostriction coefficient and strain sensitivity is suitable for device applications.</p>1 aAnantharamaiah, P., N.1 aJoy, P., A.  uhttps://library.ncl.res.in/content/magnetic-and-magnetostrictive-properties-aluminium-substituted-cobalt-ferrite-synthesized01760nas a2200157   4500008004100000022001400041245016800055210006900223260011000292300001600402490000700418520099400425100002701419700002501446856013101471       2016                        eng d  a1463-907600aEnhancing the strain sensitivity of CoFe2O4 at low magnetic fields without affecting the magnetostriction coefficient by substitution of small amounts of Mg for Fe0 aEnhancing the strain sensitivity of CoFe2O4 at low magnetic fiel  aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcAPR  a10516-105270 v183 a<p>Attaining high magnetostrictive strain sensitivity (d lambda/dH) with high magnetostriction strain (lambda) is desirable for sintered polycrystalline cobalt ferrite for various applications. It is shown that substitution of a small amount of Fe3+ by Mg2+ in CoMgxFe2-xO4 (x &lt; 0.1) gives a comparable maximum magnetostriction coefficient to that of the unsubstituted counterpart, with large improvement in the strain sensitivity at relatively low magnetic fields. A large increase in the magnetostriction coefficient is obtained at low magnetic fields for the substituted compositions. The magnetostriction parameters are further enhanced by magnetic field annealing of the sintered products. The results are analyzed based on powder XRD, Raman spectroscopy, XPS and magnetic measurements and based on the results from these studies, the changes in the magnetostriction parameters are correlated with the changes in the cation distribution, magnetic anisotropy and microstructure.</p>1 aAnantharamaiah, P., N.1 aJoy, Pattayil, Alias  uhttps://library.ncl.res.in/content/enhancing-strain-sensitivity-cofe2o4-low-magnetic-fields-without-affecting-magnetostriction02433nas a2200145   4500008004100000245017200041210006900213260000800282300002700290490000700317520179100324100002702115700001602142856012902158       2017                        eng d00a Effect of size and site preference of trivalent non-magnetic metal ions (Al3+, Ga3+, In3+) substituted for Fe3+ on the magnetostrictive properties of sintered CoFe2O40 aEffect of size and site preference of trivalent nonmagnetic meta  cNOV  aArticle Number: 4350050 v503 aThe influence of size and crystallographic site preference of three non-magnetic isovalent metal ions of larger (In3+), comparable (Ga3+) and smaller (Al3+) sizes, substituted for Fe3+ in the spinel lattice of CoFe2O4 on its magnetostrictive properties is compared. For the different compositions in CoFe2-xMxO4 (M = In3+, Ga3+, Al3+ and 0 <= x <= 0.3), significant changes in the structural and magnetic parameters are observed with the degree of substitution, due to the size and site preferences. Magnetic and Raman spectral studies revealed that Al3+ is substituted for Fe3+ at both octahedral and tetrahedral sites for all compositions, whereas In3+ and Ga3+ are substituted for Fe3+ at the tetrahedral site only for x <= 0.2 and partly at the octahedral site for x > 0.2. Regardless of the differences in the ionic size, site preference and the magnetic properties, compositions in all three series with x = 0.1 showed almost equal magnitude of maximum magnetostriction (lambda(max) = similar to 230 ppm), marginally higher than that of x = 0 (217 ppm). However, at higher substituted compositions, lambda(max) is decreased with x, but the decrease is much faster for the Al-substituted compositions. The maximum strain sensitivity, [d lambda/dH](max), is also found to be comparable for all three compositions. The comparable magnetostriction characteristics and high strain at low magnetic fields for different substituted compositions at low levels of substitution are attributed to the local structural distortions associated with the inhomogeneous distribution of the substituted ions in the spinel ferrite lattice. The studies suggest ways to optimise the magnetostriction properties of properly substituted sintered cobalt ferrite for applications in sensors and actuators.1 aAnantharamaiah, P., N.1 aJoy, P., A.  uhttps://library.ncl.res.in/content/effect-size-and-site-preference-trivalent-non-magnetic-metal-ions-al3-ga3-in3-substituted01434nas a2200217   4500008004100000022001400041245010000055210006900155260000900224300001200233490000800245520067900253653001900932653002900951653002300980653002101003653001701024100002701041700001601068856013201084       2017                        eng d  a0167-577X00aHigh magnetostriction parameters of sintered and magnetic field annealed Ga-substituted CoFe2O40 aHigh magnetostriction parameters of sintered and magnetic field   cAPR   a169-1720 v1923 a<p>Impact of substitution of the non-magnetic ion Ga3+ for Fe3+ on the magnetostriction parameters of CoFe2O4 has been investigated for samples prepared by a tartrate-gel method. All the Ga-substituted compositions in CoGaxFe2-xO4 (0 &lt;= x &lt;= 0.3) showed higher strain sensitivity (d lambda/dH), at low magnetic fields, compared to that of the unsubstituted sample. The magnetostriction strain (lambda) and d lambda/dH of the composition CoGa0.1Fe1.9O4 could be enhanced from -228 to -296 ppm and -2.20 x 10(-9) to -3.55 x 10(-9) miA, respectively, at low magnetic fields, after magnetic field annealing at 300 degrees C. (C) 2016 Elsevier B.V. All rights reserved.</p>10aCobalt ferrite10aMagnetic field annealing10aMagnetic materials10aMagnetostriction10aSubstitution1 aAnantharamaiah, P., N.1 aJoy, P., A.  uhttps://library.ncl.res.in/content/high-magnetostriction-parameters-sintered-and-magnetic-field-annealed-ga-substituted-cofe2o402151nas 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-divalent01898nas a2200145   4500008004100000245009300041210006900134260000800203300001200211490000800223520137300231100002701604700001601631856010501647       2019                        eng d00aEffect of co-substitution of Co2+ and V5+ for Fe3+ on the magnetic properties of CoFe2O40 aEffect of cosubstitution of Co2 and V5 for Fe3 on the magnetic p  cFEB  a107-1130 v5543 aDifferent chemical compositions in Co1+2xVxFe2-3xO4 (0 ≤ x ≤ 0.1) have been synthesized by the conventional solid-state reaction method and processed under identical conditions. The materials are investigated to assess the impact of change in the oxidation states of metal ions on structural and magnetic properties of cobalt ferrite. Rietveld refinement of the X-ray diffraction patterns revealed a single phase nature of all compositions with cubic spinel structure. The cubic lattice parameter was found to decrease non-linearly from 8.393 Å for x = 0 to 8.377 Å for x = 0.1, due to the effect of ionic size and valency of the substituted metal ions. Sintered co-substituted compositions exhibited smaller grains against unsubstituted counterpart, due to low melting point of raw material V2O5. Strong experimental evidence of V substitution for Fe at the tetrahedral sites of the spinel ferrite has been extracted from the Raman spectral analysis. Saturation magnetization (Ms) was observed to decrease from 452 kA/m for x = 0–411 kA/m for x = 0.1. Coercivity (Hc) and magnetocrystalline anisotropy (K1) were also found to follow the same trend. Variation of the structural and magnetic parameters is attributed to the changes in the oxidation state of Co from 2 + to 3 + as it is confirmed from the results of XPS analysis.1 aAnantharamaiah, P., N.1 aJoy, P., A.  uhttps://library.ncl.res.in/content/effect-co-substitution-co2-and-v5-fe3-magnetic-properties-cofe2o401418nas a2200193   4500008004100000022001400041245010400055210006900159260000900228300001200237490000800249520074400257653001301001653002401014653002301038100002701061700001601088856012001104       2019                        eng d  a0167-577X00aLarge enhancement in the magnetostriction parameters of the composite of CoFe2O4 and CoFe1.9Ga0.1O40 aLarge enhancement in the magnetostriction parameters of the comp  cFEB   a303-3060 v2363 a<p>A new strategy to enhance the magnetostriction parameters of cobalt ferrite (CoFe2O4) is illustrated. A composite comprising of nanocrystalline CoFe2O4 and bulk CoFe(1.9)Ga(0.1)O(4 )powders were mixed together then compacted and sintered at 1450 degrees C for 10 min. For a composite of 70 wt% CoFe2O4 and 30 wt% of CoFe(1.9)Ga(0.1)O4, maximum magnetostriction coefficient (lambda(max)) of -350 ppm has been obtained at lower magnetic field which is nearly 20% and 65% higher than that obtained for CoFe2O4 and CoFe1.9Ga0.1O4, respectively. Moreover, the composite exhibited higher strain sensitivity [d lambda/dH](max )of -2.6 x 10 (9) A(-1) m against the individual components of the composite. (C) 2018 Published by Elsevier B.V.</p>10aCeramics10aComposite materials10aMagnetic materials1 aAnantharamaiah, P., N.1 aJoy, P., A.  uhttps://library.ncl.res.in/content/large-enhancement-magnetostriction-parameters-composite-cofe2o4-and-cofe19ga01o401619nas a2200229   4500008004100000022001400041245010500055210006900160260000800229300001600237490000700253520083900260653001301099653002301112653002001135653002001155653002201175100002201197700002701219700001601246856012701262       2019                        eng d  a0272-884200aMagnetic parameters of SrFe12O19 sintered from a mixture of nanocrystalline and micron-sized powders0 aMagnetic parameters of SrFe12O19 sintered from a mixture of nano  cJUL  a13592-135960 v453 a<p>Obtaining higher magnetic parameters is essential for high-power sintered strontium ferrite (SrFe12O19) for various applications. A novel approach has been made to improve the magnetic parameters of sintered strontium ferrite by making self-composites from nano and micron-sized powders. Powders with two different weight ratios (50 wt% nano:50 wt% micron and 75 wt% nano:25 wt% micron) were mixed together, compacted and sintered at 1200 degrees C for 1 h. For a self-composite of 75 wt% nano and 25 wt% micron-sized powders, coercivity (H-c) of 3076 Oe has been obtained, larger than the values for the sintered compacts from the component powders. The present study suggests that the magnetic parameters of sintered SrFe12O19 can be improved by making self-composite comprising of nanocrystalline and micron-sized powders.</p>
10aCeramics10aMagnetic materials10amicrostructures10aSelf-composites10astrontium ferrite1 aShashanka, H., M.1 aAnantharamaiah, P., N.1 aJoy, P., A.  uhttps://library.ncl.res.in/content/magnetic-parameters-srfe12o19-sintered-mixture-nanocrystalline-and-micron-sized-powders