@article { ISI:000269638800052, title = {Magnetic characteristics of nanocrystalline multiferroic BiFeO3 at low temperatures}, journal = {Physical Review B}, volume = {80}, number = {6}, year = {2009}, month = {AUG}, pages = {064423}, publisher = {AMER PHYSICAL SOC}, address = {ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA}, abstract = {

The magnetic characteristics of nanocrystalline BiFeO3 with average crystallite sizes of similar to 50 and similar to 100 nm are evaluated by studying the temperature and field dependence of magnetization at low temperatures. Different properties such as magnetization, coercivity, and remanence show evidence for changes in the magnetic properties associated with the phase transitions at low temperatures, reported from Raman studies. Detailed field-cooled and zero-field-cooled magnetization measurements show that the likely origin of the changes in the magnetic characteristics is from the changes in the domain structure.

}, keywords = {bismuth compounds, coercive force, crystallites, magnetic domains, magnetic transitions, Multiferroics, Nanostructured materials, Raman spectra, remanence}, issn = {1098-0121}, doi = {10.1103/PhysRevB.80.064423}, author = {Vijayanand, S. and Mahajan, Mangesh B. and Potdar, H. S. and Joy, Pattayil Alias} } @article { ISI:000265933700042, title = {Origin of high room temperature ferromagnetic moment of nanocrystalline multiferroic BiFeO3}, journal = {Applied Physics Letters}, volume = {94}, number = {18}, year = {2009}, month = {MAY}, pages = {182507}, publisher = {AMER INST PHYSICS}, address = {CIRCULATION \& FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA}, abstract = {

Single phase nanocrystalline BiFeO3 of average crystallite size similar to 25 nm with very high magnetization at room temperature is synthesized by an autocombustion method. Magnetic measurements above room temperature show deviation between field cooled and zero field cooled magnetization below 645 K, the Neel temperature (T-N) of the bulk material, indicating intrinsic nature of ferromagnetism. However, observation of a broad magnetic transition above T-N of BiFeO3 and extended up to 800 K suggests the presence of Fe3O4 as a possible magnetic impurity phase. Evidence for the presence of Fe3O4 is obtained from detailed analysis of the powder x-ray diffraction pattern.

}, keywords = {bismuth compounds, Combustion synthesis, crystallites, ferromagnetic materials, high-temperature effects, magnetic impurities, Magnetic moments, Magnetisation, Multiferroics, Nanostructured materials, Neel temperature, X-ray diffraction}, issn = {0003-6951}, doi = {10.1063/1.3132586}, author = {Vijayanand, S. and Potdar, H. S. and Joy, Pattayil Alias} } @article { ISI:000273689600061, title = {Magnetic and dielectric properties and Raman spectroscopy of GdCrO3 nanoparticles}, journal = {Journal of Applied Physics}, volume = {107}, number = {1}, year = {2010}, month = {JAN}, pages = {013912}, publisher = {AMER INST PHYSICS}, address = {CIRCULATION \& FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA}, abstract = {

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.

}, keywords = {dielectric losses, gadolinium compounds, Magnetisation, Multiferroics, nanofabrication, Nanoparticles, permittivity, phonons, Raman spectra, superexchange interactions}, issn = {0021-8979}, doi = {10.1063/1.3275926}, author = {Jaiswal, Adhish and Das, Raja and Vivekanand, K. and Maity, Tuhin and Abraham, Priya Mary and Adyanthaya, Suguna D. and Poddar, Pankaj} } @article { ISI:000307039700023, title = {Enhanced magnetic parameters in the morphotropic phase boundary region of nanocrystalline multiferroic Bi1-xLaxFeO3}, journal = {Solid State Communications}, volume = {152}, number = {16}, year = {2012}, month = {AUG}, pages = {1609-1612}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {

Antiferromagnetic multiferroic BiFeO3 shows ferromagnetic characteristics by simultaneous substitution of Bi by La and decrease in the particle size to nanometer dimensions. Large changes in saturation and remnant magnetization, magnetic susceptibility at low and high fields, along with some anomalous changes in the magnetic transition temperature are observed in nanocrystalline Bi1-xLaxFeO3 system for 0.1 \<= x \<= 0.2. This compositional region corresponds to the morphotropic phase boundary (MPB) region separating the rhombohedral and orthorhombic phases, and the effect is similar to that observed in many ferroelectric systems. The present observation of enhanced ferromagnetic parameters in the MPB region of the nanocrystalline multiferroic La substituted BiFeO3 system, combined with the known ferroelectric characteristics, is suitable for future device applications. (C) 2012 Elsevier Ltd. All rights reserved.

}, keywords = {Bismuth ferrite, magnetic properties, Multiferroics, Nanocrystalline materials}, issn = {0038-1098}, doi = {10.1016/j.ssc.2012.05.011}, author = {Thakuria, P. and Joy, Pattayil Alias} } @article {49915, title = {Influence of ionic radius on structural, optical and multiferroic properties of RMnO3 [R= Y, Er, Yb] hexamanganites}, journal = {Physica B-Condensed Matter}, volume = {714}, year = {2025}, month = {OCT}, pages = {417496}, type = {Article}, abstract = {

The crystalline samples of YMnO3, ErMnO3, and YbMnO3 were synthesized by a conventional solid-state reaction technique. The single-phase hexagonal structure with the P63cm space group was verified by X-ray diffraction (XRD) study. Morphological studies show that the grains are uniform and closely packed, and that the grain size increases as the ionic radii of the rare-earth ions decrease of rare earth ions and the samples are in the stoichiometry. From the Diffused Reflectance Spectroscopy study, narrow optical band gap is observed for all the samples. Magnetic phase transitions, corresponding to the antiferromagnetic ordering, were detected for all samples. The Neel temperature was found to increase with the decrease of the ionic radii of A site element in RMnO3 (Y, Er, and Yb) samples. Ferroelectric hysteresis loops at room temperature as a function of applied electric fields reveal the leaky behaviour. The dielectric constant and dielectric loss tangent variation across different frequencies are also explored for these samples. A summary and discussion of the structural, optical, magnetic and ferroelectric properties, underlying physical mechanisms, the role of the rare earth ions, and the complex interactions in hexagonal manganites, are presented in this paper. This work emphasizes how systematic variation of A-site ionic radii influences the multiferroic properties of RMnO3, gaining thorough insights into structure-property relationships that are essential to design multifunctional materials.

}, keywords = {Antiferromagnetic, ferroelectric, Multiferroics, Perovskites, Photovoltaic, Recombination centers}, issn = {0921-4526}, doi = {10.1016/j.physb.2025.417496}, author = {Inchara, D. R. and Singh, Kirandeep and Sangole, Mayur and Murari, M. S. and Daivajna, Mamatha D.} }