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Tapan Chatterji

Bio: Tapan Chatterji is an academic researcher from Forschungszentrum Jülich. The author has contributed to research in topics: Antiferromagnetism & Inelastic neutron scattering. The author has an hindex of 32, co-authored 207 publications receiving 4059 citations. Previous affiliations of Tapan Chatterji include Centre national de la recherche scientifique & Indian National Association.


Papers
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Journal ArticleDOI
TL;DR: This work shows that the key structural features in BaFe2As2, namely suppression of the tetragonal-to-orthorhombic phase transition and reduction in the As-Fe-As bond angle and Fe-Fe distance, show the same behaviour under pressure as found in chemically substituted samples, and suggests that modification of the Fermi surface by structural distortions is more important than charge doping for inducing superconductivity in Ba Fe 2As2.
Abstract: The discovery of a new family of high-T(C) materials, the iron arsenides (FeAs), has led to a resurgence of interest in superconductivity. Several important traits of these materials are now apparent: for example, layers of iron tetrahedrally coordinated by arsenic are crucial structural ingredients. It is also now well established that the parent non-superconducting phases are itinerant magnets, and that superconductivity can be induced by either chemical substitution or application of pressure, in sharp contrast to the cuprate family of materials. The structure and properties of chemically substituted samples are known to be intimately linked; however, remarkably little is known about this relationship when high pressure is used to induce superconductivity in undoped compounds. Here we show that the key structural features in BaFe2As2, namely suppression of the tetragonal-to-orthorhombic phase transition and reduction in the As-Fe-As bond angle and Fe-Fe distance, show the same behaviour under pressure as found in chemically substituted samples. Using experimentally derived structural data, we show that the electronic structure evolves similarly in both cases. These results suggest that modification of the Fermi surface by structural distortions is more important than charge doping for inducing superconductivity in BaFe2As2.

225 citations

Journal ArticleDOI
TL;DR: In this article, a high-quality single crystal of CaFe (CaFe 2, AsFe 2 ) is reported, where a sharp transition was observed between the high-temperature tetragonal and lowtemperature orthorhombic structures at T =172.5 and 173.5 K, respectively, between cooling and warming.
Abstract: Neutron diffraction measurements of a high-quality single crystal of ${\text{CaFe}}_{2}{\text{As}}_{2}$ are reported. A sharp transition was observed between the high-temperature tetragonal and low-temperature orthorhombic structures at ${T}_{S}=172.5\text{ }\text{K}$ (on cooling) and 173.5 K (on warming). Concomitant with the structural transition, the Fe moments order in a commensurate antiferromagnetic structure with a saturated moment of $0.80(5){\ensuremath{\mu}}_{B}/\text{Fe}$ directed along the orthorhombic $a$ axis. The hysteresis of both the structural and magnetic transitions is 1 K between cooling and warming, consistent with previous thermodynamic, transport, and single-crystal x-ray studies and provides clear evidence of the coupling between the structural and magnetic transitions in this material.

208 citations

Book
01 Jan 2006
TL;DR: In this paper, Chatterji et al. presented a representation analysis of magnetic structures and proposed a method for representing the structure of the magnetic structures of the objects in the image.
Abstract: Preface List of Contributors 1. Magnetic Neutron Scattering (T. Chatterji) 2. Magnetic Structures (T. Chatterji) 3. Representation Analysis of Magnetic Structures (R. Ballou and B. Ouladdiaf) 4. Polarized Neutrons and Polarization Analysis (J. Schweizer) 5. Spherical Neutron Polarimetry (P.J. Brown) 6. Magnetic Excitations (T. Chatterji) 7. Paramagnetic and Critical Scattering (T. Chatterji) 8. Inelastic Neutron Polarization Analysis (L.P. Regnault) 9. Polarized Neutron Reflectometry (C.F. Majkrzak, K.V. ODonovan and N.F. Berk) 10. Small Angle Neutron Scattering Investigations of Magnetic Nanostructures (A. Wiedenmann) 11. Neutron-Spin-Echo Spectroscopy and Magnetism (C. Pappas, G. Ehlers and F. Mezei) Author Index Subject Index

142 citations

Journal ArticleDOI
TL;DR: In this article, the structural and property measurements of nanocrystals of half-doped La 05 Ca 05 MnO 3 (LCMO) synthesized by chemical route, having particle size down to an average diameter of 15 nm, were reported.
Abstract: In this paper we report the structural and property (magnetic and electrical transport) measurements of nanocrystals of half-doped La 05 Ca 05 MnO 3 (LCMO) synthesized by chemical route, having particle size down to an average diameter of 15 nm It was observed that the size reduction leads to change in crystal structure, and the room temperature structure is arrested so that the structure does not evolve on cooling unlike bulk samples The structural change mainly affects the orthorhombic distortion of the lattice By making comparison to observed crystal structure data under hydrostatic pressure, it is suggested that the change in the crystal structure of the nanocrystals occurs due to an effective hydrostatic pressure created by the surface pressure on size reduction This not only changes the structure but also causes the room temperature structure to freeze The size reduction also does not allow the long supercell modulation needed for the charge ordering, characteristic of this half-doped manganite, to set in The magnetic and transport measurements also show that the charge ordering (CO) does not occur when the size is reduced below a critical size Instead, the nanocrystals show ferromagnetic ordering down to the lowest temperatures along with metallic-type conductivity Our investigation establishes a structural basis for the destabilization of CO state observed in half-doped manganite nanocrystals

139 citations


Cited by
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01 Sep 1955
TL;DR: In this paper, the authors restrict their attention to the ferrites and a few other closely related materials, which are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present.
Abstract: In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

2,659 citations

Journal ArticleDOI
TL;DR: PDFfit2 is a program as well as a library for real-space refinement of crystal structures capable of fitting a theoretical three-dimensional structure to atomic pair distribution function data and is ideal for nanoscale investigations.
Abstract: PDFfit2 is a program as well as a library for real-space refinement of crystal structures. It is capable of fitting a theoretical three-dimensional (3D) structure to atomic pair distribution function data and is ideal for nanoscale investigations. The fit system accounts for lattice constants, atomic positions and anisotropic atomic displacement parameters, correlated atomic motion, and experimental factors that may affect the data. The atomic positions and thermal coefficients can be constrained to follow the symmetry requirements of an arbitrary space group. The PDFfit2 engine is written in C++ and is accessible via Python, allowing it to inter-operate with other Python programs. PDFgui is a graphical interface built on the PDFfit2 engine. PDFgui organizes fits and simplifies many data analysis tasks, such as configuring and plotting multiple fits. PDFfit2 and PDFgui are freely available via the Internet.

1,483 citations

Journal ArticleDOI
TL;DR: The response of the worldwide scientific community to the discovery in 2008 of superconductivity at T c'='26'K in the Fe-based compound LaFeAsO1−x F x has been very enthusiastic.
Abstract: The response of the worldwide scientific community to the discovery in 2008 of superconductivity at T c = 26 K in the Fe-based compound LaFeAsO1−x F x has been very enthusiastic. In short order, ot...

1,373 citations