03023nas a2200337 4500008004100000022001400041245008600055210006900141260012500210300001100335490000800346520187100354653002202225653002502247653001802272653001802290653002002308653001802328653001702346653001202363653001802375653003102393100002002424700001402444700001902458700001702477700002502494700002702519700001902546856012002565 2010 eng d a0021-897900aMagnetic and dielectric properties and Raman spectroscopy of GdCrO3 nanoparticles0 aMagnetic and dielectric properties and Raman spectroscopy of GdC aCIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USAbAMER INST PHYSICScJAN a0139120 v1073 a

The rare earth orthochromites are extremely interesting due to the richness of their optical, dielectric, and magnetic properties as well as due to their multiferroic properties which make them suitable materials to study in the nanoregime. However, the wet-chemical synthesis of these materials in nanosize is nontrivial. Here, we report for the first time, the detailed Raman spectra as well as magnetic and dielectric properties of chemically synthesized GdCrO3 nanoparticles of size ranging from 40 to 60 nm. The magnetic properties are dictated by competing Cr3+-Cr3+, Gd3+-Cr3+, and Gd3+-Gd3+ superexchange interactions in different temperature regions, resulting into an antiferromagnetic ordering at 167 K due to the Cr3+-Cr3+ followed by weak ferromagnetic ordering due to the onset of Cr3+-Gd3+ interactions. At lower temperature, it shows weak antiferromagnetic ordering due to Gd3+-Gd3+ interaction. Below 95 K, GdCrO3 nanoparticles showed the presence of negative magnetization due to Gd3+ and Cr3+ interactions resulting into weak ferromagnetic coupling. The Raman spectroscopy shows the characteristic Raman shifts indicating that below 450 cm(-1), Gd3+ ions play a dominant role in determining the phonon frequencies of GdCrO3, and above 450 cm(-1), the Cr+3 ions dominate. We also present for the first time the low temperature dielectric constant and loss tangent data for GdCrO3 in a broad temperature and frequency range. The dielectric constant shows a decrease in comparison to the bulk values due to the size dependent effects. It also shows a peak centered at around 320 K above which it shows a sharp decrease. The dielectric loss value in GdCrO3 nanoparticles is quite small and shows an interesting frequency dependent anomaly at lower temperature which might be due to the coupling between magnetic and dielectric order parameters.

10adielectric losses10agadolinium compounds10aMagnetisation10aMultiferroics10ananofabrication10aNanoparticles10apermittivity10aphonons10aRaman spectra10asuperexchange interactions1 aJaiswal, Adhish1 aDas, Raja1 aVivekanand, K.1 aMaity, Tuhin1 aAbraham, Priya, Mary1 aAdyanthaya, Suguna, D.1 aPoddar, Pankaj uhttps://library.ncl.res.in/content/magnetic-and-dielectric-properties-and-raman-spectroscopy-gdcro3-nanoparticles-002541nas a2200205 4500008004100000022001400041245014000055210006900195260007100264300001600335490000800351520173100359100002002090700001402110700001702124700001902141700002702160700001902187856012902206 2010 eng d a1932-744700aTemperature-dependent raman and dielectric spectroscopy of BiFeO3 nanoparticles: signatures of spin-phonon and magnetoelectric coupling0 aTemperaturedependent raman and dielectric spectroscopy of BiFeO3 a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcJUL a12432-124390 v1143 a

We report the temperature-dependent Raman and dielectric spectroscopy of chemically synthesized BiFeO3 nanoparticles (average size similar to 50-60 nm). The Raman spectra (90-700 K) show two sets of transitions in the lowest Raman E mode, associated with Bi-O bond motion situated in close proximity to the spin reorientation transitions reported for BiFeO3, thereby indicating the existence of possible coupling between magnons and phonons for particle size below the helical order parameter (62 nm). These transitions are slightly shifted in temperature in comparison to the bulk single crystals. We also observe a step-like behavior in Raman peak position around the Neel temperature, suggesting that the phonons are influenced by the magnetic ordering in nanosized BiFeO3. The heat-flow measurements show two sharp endothermic peaks at 1094 and 1223 K representing rhombohedral to orthorhombic or monoclinic transition followed by transition into the cubic phase above 1200K. The low temperature (20-325 K), frequency-dependent (1-10(6) Hz) dielectric constant and loss tangent measurements show that the loss tangent (similar to 10(-3)) and ac conductivity values (similar to 10(-8) Ohm(-1)-cm(-1)) are orders of magnitude lower than the reported values for BiFeO3 ceramics, indicating high levels of ionic purity of our samples. The real part of the permittivity shows a slight reduction in its value (similar to 30) in comparison to the bulk single crystals. Similar to the Stokes Raman shift, its temperature-dependent dielectric constant also shows four weak anomalies at similar to 85, 168, 205, and 230 K situated in close proximity to the spin reorientation transitions, indicating magnetoelectric coupling.

1 aJaiswal, Adhish1 aDas, Raja1 aMaity, Tuhin1 aVivekanand, K.1 aAdyanthaya, Suguna, D.1 aPoddar, Pankaj uhttps://library.ncl.res.in/content/temperature-dependent-raman-and-dielectric-spectroscopy-bifeo3-nanoparticles-signatures-001989nas a2200181 4500008004100000022001400041245006800055210006800123260012500191300001100316490000800327520130000335100002001635700001401655700001701669700001901686856010201705 2011 eng d a0021-897900aDielectric and spin relaxation behaviour in DyFeO3 nanocrystals0 aDielectric and spin relaxation behaviour in DyFeO3 nanocrystals aCIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USAbAMER INST PHYSICScDEC a1243010 v1103 a

We report the temperature and frequency dependent dielectric measurements and ac magnetic susceptibility of chemically synthesized DyFeO3 nanoparticles (size similar to 50-60 nm). The measurement of the dielectric properties was carried out in a broad temperature (20-325 K) and frequency (1-10(6) Hz) range. The non-Debye type dipolar relaxation phenomenon was observed in the DyFeO3 nanoparticles, as confirmed by the Cole-Cole plots. The higher values of epsilon' at the lower frequencies are explained on the basis of the Maxwell-Wagner model. The Cole-Cole analysis enabled us to separate the contribution of relaxation times, resistance and capacitance in grain and grain boundaries in DyFeO3 nanocrystals. We found that with increasing temperature, the contribution of grain boundary resistance increases in comparison to the grain resistance. We also performed spin relaxation studies in a broad temperature and frequency range. Both the in-phase (chi') and out-of-phase (chi `') components of the ac magnetic susceptibilities of the DyFeO3 nanoparticles show a clear evidence at spin reorientation transition around 70K and T-N (Dy) around 4K as reported by us in our earlier study using the dc magnetic behaviour. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3669154]

1 aJaiswal, Adhish1 aDas, Raja1 aMaity, Tuhin1 aPoddar, Pankaj uhttps://library.ncl.res.in/content/dielectric-and-spin-relaxation-behaviour-dyfeo3-nanocrystals-001635nas a2200253 4500008004100000022001400041245008700055210006900142260010600211300001000317490000800327520071300335653002201048653001501070653002901085653001801114100003401132700002601166700001401192700001701206700001901223700002101242856011801263 2011 eng d a0038-109800aInvestigations of magnetic and dielectric properties of cupric oxide nanoparticles0 aInvestigations of magnetic and dielectric properties of cupric o aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLANDbPERGAMON-ELSEVIER SCIENCE LTDcJAN a55-600 v1513 a

Cupric oxide nanoparticles of similar to 8-10 nm width and 40-45 nm length self assembled as large particles similar to 1-1 5 mu m have been investigated in the 10-325 K temperature range using magnetic and dielectric measurements In magnetic measurements a single broad peak at similar to 230 K in a zero field cooled sample has been observed Coercivity in magnetization measurements at 10 K suggests that the nanoparticles are core-shell type particles with an antiferromagnetic core and a ferromagnetic shell Dielectric measurements at various frequencies from 3 7 Hz to 949 kHz exhibit a sharp peak at 284 K followed by weak anomalies around 213 and 230 K (C) 2010 Elsevier Ltd All rights reserved

10aCuO nanoparticles10aDielectric10aFerroelectric transition10aFerromagnetic1 aBhalerao-Panajkar, Rohini, S.1 aShirolkar, Mandar, M.1 aDas, Raja1 aMaity, Tuhin1 aPoddar, Pankaj1 aKulkarni, S., K. uhttps://library.ncl.res.in/content/investigations-magnetic-and-dielectric-properties-cupric-oxide-nanoparticles-002832nas a2200193 4500008004100000022001400041245014300055210006900198260007100267300001600338490000800354520204500362100002602407700001402433700001702447700001902464700002602483856012902509 2012 eng d a1932-744700aObservation of enhanced dielectric coupling and room-temperature ferromagnetism in chemically synthesized BiFeO3@SiO2 core-shell particles0 aObservation of enhanced dielectric coupling and roomtemperature  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcSEP a19503-195110 v1163 a

We report the effect of SiO2 coating on the structural, magnetic, and dielectric properties of chemically synthesized high-purity BiFeO3 particles. The assynthesized BiFeO3 particles demonstrate properties comparable with those reported for bulk BiFeO3. On the other hand, the structural measurement on BiFeO3@SiO2 shows that the SiO2 coating has anisotropically compressed the lattice of BiFeO3 particles and stimulates the variation in the electron density. This affects magnetic and dielectric behavior of material. Frequency-dependent dielectric constant study at low temperature (20-325 K) revealed slight reduction (8-10%) in the dielectric constant of BiFeO3@SiO2 particles compared to uncoated BiFeO3 particles. The study reveals five anomalies at 234, 206, 146, 84, and 25 K located in close proximity to the linear magnetodielectric coupling and spin reorientation transitions. The loss tangent (approximate to 10(-3)) and alternating current (ac) conductivity (approximate to 10(-8) Omega(-1)cm(-1)) of BiFeO3@SiO2 particles are orders of magnitude lower than those observed for the BiFeO3 particles. The magnetic measurement shows the existence of room-temperature ferromagnetism in BiFeO3@SiO2 particles with average value of magnetic moment per Fe atom approximate to 0.030 mu(B) and appreciable coercivity as high as 120 Oe. The canted spin structure in the surface shell of BiFeO3@SiO2 particles show an enhanced magnetic property and shifted hysteresis loop. The magnetic measurement in close proximity to dielectric transitions revealed enhanced magnetization, suggesting the presence of anisotropies. It has been observed that SiO2 coating alters the properties of BiFeO3 particles. Our dielectric and magnetic measurements show enhanced coupling among the electric and magnetic ordered parameters in BiFeO3@SiO2 core-shell particles compared to uncoated BiFeO3 particles. The magnetic and dielectric properties of SiO2-coated BiFeO3 are similar to nanoparticles of BiFeO3 where interface plays a significant role.

1 aShirolkar, Mandar, M.1 aDas, Raja1 aMaity, Tuhin1 aPoddar, Pankaj1 aKulkarni, Sulabha, K. uhttps://library.ncl.res.in/content/observation-enhanced-dielectric-coupling-and-room-temperature-ferromagnetism-chemically-0