Search

Your search keyword '"Ray, Sugata"' showing total 16 results
Start Over Author "Ray, Sugata" Publisher iop publishing
16 results on '"Ray, Sugata"'

14. Defect controlled room temperature ferromagnetism in Co-doped barium titanate nanocrystals.

Author

Ray, Sugata, Kolen'ko, Yury V., Kovnir, Kirill A., Lebedev, Oleg I., Turner, Stuart, Chakraborty, Tanushree, Erni, Rolf, Watanabe, Tomoaki, Van Tendeloo, Gustaaf, Yoshimura, Masahiro, and Itoh, Mitsuru

Subjects
*NANOCRYSTALS, *FERROMAGNETISM, *TEMPERATURE effect, *SURFACE defects, *DOPED semiconductors, *BARIUM titanate, *HYDROXYL group
Abstract

Defect mediated high temperature ferromagnetism in oxide nanocrystallites is the central feature of this work. Here, we report the development of room temperature ferromagnetism in nanosized Co-doped barium titanate particles with a size of around 14 nm, synthesized by a solvothermal drying method. A combination of x-ray diffraction with state-of-the-art electron microscopy techniques confirms the intrinsic doping of Co into BaTiO3. The development of the room temperature ferromagnetism was tracked down to the different donor defects, namely hydroxyl groups at the oxygen site (OH·(O)) and oxygen vacancies (V··(O)), and their relative concentrations at the surface and the core of the nanocrystal, which could be controlled by post-synthesis drying and thermal treatments. [ABSTRACT FROM AUTHOR]

Published
2012
Full Text
View/download PDF

16. Development of half metallicity within mixed magnetic phase of Cu1−xCoxMnSb alloy

Author

Atanu Paul, Indra Dasgupta, S. K. Neogi, Abhisek Bandyopadhyay, Carlo Meneghini, Sudipta Bandyopadhyay, Sugata Ray, Bandyopadhyay, Abhisek, Neogi, Swarup Kumar, Paul, Atanu, Meneghini, Carlo, Bandyopadhyay, Sudipta, Dasgupta, Indra, and Ray, Sugata

Subjects
magnetic transition, Materials science, Magnetoresistance, FOS: Physical sciences, 02 engineering and technology, half metallicity, 01 natural sciences, Condensed Matter - Strongly Correlated Electrons, Condensed Matter::Materials Science, symbols.namesake, chemistry.chemical_compound, 0103 physical sciences, electronic transition, Antiferromagnetism, General Materials Science, 010306 general physics, Electronic band structure, Density Functional Theory, Strongly Correlated Electrons (cond-mat.str-el), Condensed matter physics, Fermi level, Fermi surface, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Ferromagnetism, chemistry, symbols, Condensed Matter::Strongly Correlated Electrons, Materials Science (all), 0210 nano-technology, Ground state, AFm phase
Abstract

Cubic Half-Heusler Cu$_{1-x}$Co$_x$MnSb (0 $\leq$ $x$ $\leq$ 0.1) compounds have been investigated both experimentally and theoretically for their magnetic, transport and electronic properties in search of possible half metallic antiferromagnetism. The systems (Cu,Co)MnSb are of particular interest as the end member alloys CuMnSb and CoMnSb are semi metallic (SM) antiferromagnetic (AFM) and half metallic (HM) ferromagnetic (FM), respectively. Clearly, Co-doping at the Cu-site of CuMnSb introduces changes in the carrier concentration at the Fermi level that may lead to half-metallic ground state but there remains a persistent controversy whether the AFM to FM transition occurs simultaneously. Our experimental results reveal that the AFM to FM magnetic transition occurs through a percolation mechanism where Co-substitution gradually suppresses the AFM phase and forces FM polarization around every dopant cobalt. As a result a mixed magnetic phase is realized within this composition range while a nearly HM band structure is developed already at the 10% Co-doping. Absence of T$^2$ dependence in the resistivity variation at low T-region serves as an indirect proof of opening up an energy gap at the Fermi surface in one of the spin channels. This is further corroborated by the ab-initio electronic structure calculations that suggests a nearly ferromagnetic half-metallic ground state is stabilized by Sb-p holes produced upon Co doping.

Published
2018
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results