@article { ISI:000287338100007, title = {Surface effects on morin transition, exchange bias, and enchanced spin reorientation in chemically synthesized DyFeO3 nanoparticles}, journal = {Journal of Physical Chemistry C}, volume = {115}, number = {7}, year = {2011}, month = {FEB}, pages = {2954-2960}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

A giant linear magnetoelectric effect was observed by Y. Tokura{\textquoteright}s group recently in multiferroic DyFeO3, which demands a detailed investigation of its magnetic properties. Additionally, there is little information on the changes of chemical and physical properties of these materials with the reduction in particle size in spite of the potential applications of these materials nanoscale devices. As the wet-chemical synthesis of these materials in nanosize and getting a control over crystallinity and stoichiometry is nontrivial and poses a serious challenge prohibiting the study of their size-dependent properties. Here, we report the synthesis of DyFeO3 nanoparticles using a surfactantless hydrothermal method with a detailed magnetic property measurement. The as-synthesized DyFeO3 nanoparticles showed excellent crystallinitywith average particle size in the range 50-60 nm. The structural analysis indicated that they are of a distorted orthorhombic pervoslcite crystal structure. Detailed dc magnetization measurements in the temperature range of 3-350 K could isolate the presence of Dy3+-Fe3+ and Dy3+-Dy3+ superexchange interactions, which showed up as spin reorientation transitions in various temperature regions due to the differing magnitude of their interactions resulting in continuous rotation of antiferromagnetic component of Fe3+ spins with cooling of the sample. Nanosized DyFeO3 showed spin-reorientation transitions near 315 and 70K due to the Dy3+-Fe3+ interaction accompanied with an opening up of the hysteresis loop followed by antiferromagnetic ordering around 4 K due to a possible Dy3+-Dy3+ interaction. We also observed significant effect of the particle size reduction on the magnetic properties. The main effects seen. by us were in terms of (1) pronounced spontaneous spin reorientation transitions, (2) the absence of Morin transition, and (3) presence of temperature-dependent exchange bias in the DyFeO3 nanoparticles. We present a detailed mechanism to explain these features based on the interplay of Dy3+ and Fe3+ spins as well surface disorder, anisotropy, canting, and so forth.

}, issn = {1932-7447}, doi = {10.1021/jp109313w}, author = {Jaiswal, Adhish and Das, Raja and Adyanthaya, Suguna D. and Poddar, Pankaj} } @article { ISI:000289003000012, title = {Synthesis and optical studies of GdCrO3 nanoparticles}, journal = {Journal of Nanoparticle Research}, volume = {13}, number = {3}, year = {2011}, month = {MAR}, pages = {1019-1027}, publisher = {SPRINGER}, address = {VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS}, abstract = {

{Here we report for the first time, a detailed synthesis mechanism of GdCrO3 nanoparticles using a surfactant-less hydrothermal method. We also report a detailed study of their structural and optical properties. The selected area electron diffraction and powder X-ray diffraction studies of GdCrO3 nanoparticles show pure phase and excellent crystallinity with average particle size around 50-60 nm. The structural analysis indicates a distorted perovskite crystal structure with lattice parameter values of a = 5.3099 +/- A 0.0022

}, keywords = {hydrothermal, Nanoparticles, Rare earth orthochromites}, issn = {1388-0764}, doi = {10.1007/s11051-010-0090-4}, author = {Jaiswal, Adhish and Das, Raja and Adyanthaya, Suguna D. and Poddar, Pankaj} } @article { ISI:000313591300016, title = {Static and dynamic magnetic properties and interplay of Dy3+, Gd3+ and Mn3+ spins in orthorhombic DyMnO3 and GdMnO3 nanoparticles}, journal = {Journal of Physics D-Applied Physics}, volume = {46}, number = {4}, year = {2013}, month = {JAN}, pages = {045301}, publisher = {IOP PUBLISHING LTD}, address = {TEMPLE CIRCUS, TEMPLE WAY, BRISTOL BS1 6BE, ENGLAND}, abstract = {

Single-phase orthorhombic DyMnO3 and GdMnO3 nanoparticles in the size range 60-70 and 35-45 nm, respectively, were synthesized using a modified hydrothermal method. The magnetic property measurements of DyMnO3 nanocrystals show anomalies around similar to 43K (antiferromagnetic (AFM) coupling between Mn3+ spins) and at 7K in the form of a peak in the zero-field-cooled curve (AFM coupling between Dy3+ spins). Whereas, GdMnO3 undergoes a phase transition at similar to 42K from paramagnetic to an incommensurate-antiferromagnetic phase (ICAFM) followed by a second anomaly at similar to 22 K, which could be associated with the transition from ICAFM into a canted A-type AFM ordering of the Mn3+ spins. This transition is followed by a long-range ordering of the Gd3+ moments at 6K yielding the canting of the Gd3+ spins with a ferromagnetic (FM) component antiparallel to the FM moment of the canted Mn3+ spins. No anomaly near the Neel temperature of the Mn moments for both DyMnO3 and GdMnO3 nanoparticles was observed in ac magnetization which were observed in dc magnetization. The room temperature Raman spectra of DyMnO3 shows two most intense Raman modes at 480 and 609 cm(-1) which can be assigned to an antisymmetric Jahn-Teller stretching mode and a symmetric or breathing stretching mode, respectively, involving Mn-O bond stretching.

}, issn = {0022-3727}, doi = {10.1088/0022-3727/46/4/045301}, author = {Das, Raja and Jaiswal, Adhish and Poddar, Pankaj} } @article { ISI:000313513400048, title = {Surface chemistry and growth mechanism of highly oriented, single crystalline TiO2 nanorods on transparent conducting oxide coated glass substrates}, journal = {RSC Advances}, volume = {3}, number = {6}, year = {2013}, month = {NOV}, pages = {1933-1940}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

The fabrication of one-dimensional (1D) rods or wires of titania in desired crystalline facets is quite exciting due to unique optoelectronic properties. The single crystalline, oriented nanorods directly grown on transparent conducting oxide (TCO) substrates are finding a lot of interest in solar photovoltaics and several other optoelectronic devices due to enhanced electron transport and lower exciton recombination rates. However, the growth of desired crystalline facets of highly oriented, single crystalline nanorods on different substrates and understanding the interplay between the surface chemistry and growth mechanism still remain a non-trivial and challenging task. Here, for the first time, the kinetically controlled growth of the (310) facet of TiO2 nanorods on fluorine-doped tin oxide (FTO) coated glass substrate has been reported which is in contrast to the previously reported (002) faceted TiO2 nanorods. In addition to this, the growth of (110) facet TiO2 nanorods using amorphous fluorine doped silicon oxide (FSO) as a substrate is also demonstrated. In this paper, it is shown that two different faceted TiO2 nanorods can be synthesized following same synthetic condition by varying only the material properties of the substrate. To investigate the role of substrate chemistry on the morphology and single crystallinity of TiO2 nanorods, electron microscopy, XPS and contact angle measurements have been done. The results clearly indicate an important link between the surface chemistry and morphology of TiO2 nanorods. It can be assumed that there is a role of OH- and water groups which are responsible for the growth of plane (110) which has less surface energy. The observation of (310) facet is quite surprising and can be explained based on FTO crystallinity. It is possible to tune the diameter of the titania nanorods by further coating the FTO substrate with a thin gold layer due to increase in the hydrophilicity of the substrate. Finally, a light to electricity conversion efficiency of 2.5\% could be achieved by using vertically grown titania nanorods on FTO as the photoanode in a dye sensitized solar cell (DSSC).

}, issn = {2046-2069}, doi = {10.1039/c2ra21516k}, author = {Sadhu, Subha and Jaiswal, Adhish and Adyanthaya, Suguna D. and Poddar, Pankaj} }