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Papers by Goutam Dev Mukherjee

Research paper thumbnail of Critical exponents of NiFeV alloys for the ferromagnetic–paramagnetic phase transition

Journal of Magnetism and Magnetic Materials, 2000

Research paper thumbnail of Critical exponents of NiFeV alloys for the ferromagnetic-paramagnetic phase transition

Journal of Magnetism and Magnetic Materials, 2000

A systematic study of the magnetic critical exponents has been made in Ni-rich NiFeV ternary allo... more A systematic study of the magnetic critical exponents has been made in Ni-rich NiFeV ternary alloys of compostions Ni 77Fe 7V 16, Ni 79Fe 5V 16 and Ni 78Fe 4V 18 in the critical region of ferromagnetic to paramagnetic (FM-PM) transition through detailed AC-susceptibiltiy and DC-magnetization measurements. In all the alloys, we have found a well-defined critical temperature TC below which the spontaneous magnetization increases with decreasing temperature. The critical exponents and critical amplitudes associated with the transitions are obtained. Their values show drastic changes from those of pure Ni.

Research paper thumbnail of High-pressure melting curve of helium and neon: Deviations from corresponding states theory

Research paper thumbnail of High-Pressure Melting Curve of Nitrogen and the Liquid-Liquid Phase Transition

Physical Review Letters, 2007

The melting curve of nitrogen was measured up to 71 GPa, a fourfold increase in pressure over pre... more The melting curve of nitrogen was measured up to 71 GPa, a fourfold increase in pressure over previous measurements. The measurements were made using the laser-heated diamond anvil cell and melting was detected in situ by the laser speckle method. The melting temperature rises linearly up to a maximum at 50 GPa and 1920 K, and with increasing pressure suddenly decreases linearly to 1400 K at 71 GPa. This sharp drop in the melting slope (dT/dP) above 50 GPa indicates the appearance of a liquid denser than the solid and of a liquid-liquid phase transition. The sharpness of the changes suggests that the transition is first order and is a liquid-liquid polymer transition. This conclusion is consistent with earlier theoretical studies and experimental evidence that pressure transforms molecular nitrogen into a chainlike polymeric form.

Research paper thumbnail of Mukherjee and Boehler Reply

Physical Review Letters, 2009

ABSTRACT A Reply to the Comment by E. Gregoryanz and A. F. Goncharov.

Research paper thumbnail of High pressure AC resistivity and compressibility study on Al 2(WO 4) 3

Journal of Physics and Chemistry of Solids, 2003

Research paper thumbnail of Reappearance of ferroelectric soft modes in the paraelectric phase of Pb1−xCaxTiO3 at high pressures: Raman and x-ray diffraction studies

Journal of Physics-condensed Matter, 2012

High pressure Raman spectroscopy and x-ray diffraction measurements have been carried out on Pb(1... more High pressure Raman spectroscopy and x-ray diffraction measurements have been carried out on Pb(1-x)Ca(x)TiO(3) (x = 0.10 and 0.30). Using high pressure Raman spectroscopic data, it is observed that the phonon instability responsible for the ferroelectric phase reappears in the paraelectric phase after a critical pressure. The observed critical pressures in the Ca(2+) doped PbTiO(3) system are much lower than the unique pressures suggested for PbTiO(3) based materials. A suitable explanation is given to explain this lowering of critical pressure. It is also shown that the ferroelectric phase which stabilizes in the paraelectric phase has a tetragonal symmetry with space group I4cm.

Research paper thumbnail of High pressure investigations of Na0.025WO3: x-ray diffraction and Raman spectroscopy studies

Journal of Physics-condensed Matter, 2011

High pressure x-ray diffraction and Raman spectroscopy studies have been carried out on non-stoic... more High pressure x-ray diffraction and Raman spectroscopy studies have been carried out on non-stoichiometric sodium tungsten bronze, Na0.025WO3. The high pressure investigations reveal a phase transition at about 2 GPa by a change of space group symmetry from P21/n to P21/c in the monoclinic cell followed by a second structural transformation to a triclinic lattice around 18 GPa. There are volume changes with these structural transformations, which are driven by rotation and significant distortion of WO6 octahedra due to the displacement of tungsten and oxygen atoms from their mean positions in the unit cell.

Research paper thumbnail of Effect of 0.18 at.% Re impurity on the Neel transition in chromium

Thermal expansion measurements are reported on Cr+0.18 at% Re alloy system near the Spin Density ... more Thermal expansion measurements are reported on Cr+0.18 at% Re alloy system near the Spin Density Wave transition at TN=318 K and incommensurate-commensurate transition at 297 K. The nature of the transition at TN is deduced to be weakly first order and a large change in anharmonicity is observed which implies a considerable lattice softening below TN.

Research paper thumbnail of Thermal expansion study of Bi2223 superconductor: an evidence of polaronic mechanism of high T c superconductivity with strong two-dimensional fluctuations

Physica C-superconductivity and Its Applications, 2000

Research paper thumbnail of Thermal Expansion of Alkali Halides:. a Semiclassical Model

Modern Physics Letters B, 1994

A simple-minded semiclassical method is used to obtain the thermal expansion of alkali halides vi... more A simple-minded semiclassical method is used to obtain the thermal expansion of alkali halides viz. KBr, KCl, Kl, and NaCl. It is observed that our theoretical prediction agrees fairly well with the available experimental data. It is furthermore suggested that the present method can be used for an accurate determination of the Debye temperature of alkali halides.

Research paper thumbnail of Anomalous thermal expansion behavior of the YBaCuO superconductor. Indirect evidence of polaron formation

Physica C-superconductivity and Its Applications, 1994

A simple-minded semiclassical method is used to study the thermal expansion data of YBa2Cu3O7-del... more A simple-minded semiclassical method is used to study the thermal expansion data of YBa2Cu3O7-delta (delta = 0.15) both in the normal and superconducting phases. It is shown that there is an anomaly in the temperature variation of the thermal expansion which begins to show up at a temperature somewhat higher than Tc. We argue that this anomaly can be attributed to the phenomenon of polaron formation. This might give an indirect support to the bipolaronic mechanism of high-temperature superconductivity.>

Research paper thumbnail of Thermal expansion analysis of Fe3-xMnxAl alloys

Physical Review B, 1998

ABSTRACT Thermal expansion measurements have been performed on the ternary alloy system, Fe3-xMnx... more ABSTRACT Thermal expansion measurements have been performed on the ternary alloy system, Fe3-xMnxAl for x=0.3, 0.9, and 1.2 to study the effect of Mn substitution on their thermal and magnetic properties. The vibrational and magnetic contributions to thermal expansion, specific heat, and entropy for these alloys have been determined using a theoretical model and various Grüneisen parameters have been obtained.

Research paper thumbnail of Effect of 0.18 at.% Re impurity on the Neel transition in chromium

ABSTRACT Thermal expansion measurements are reported on Cr+0.18 at% Re alloy syste... more ABSTRACT Thermal expansion measurements are reported on Cr+0.18 at% Re alloy system near the Spin Density Wave transition at TN=318 K and incommensurate-commensurate transition at 297 K. The nature of the transition at TN is deduced to be weakly first order and a large change in anharmonicity is observed which implies a considerable lattice softening below TN.

Research paper thumbnail of ElectronMagnetic, Lattice and Magnon Grüneisen Parameters of Iron and Nickel:. Results from Thermal Expansion Measurements and Model Calculations

International Journal of Modern Physics B, 1998

Thermal expansion measurements have been performed on nickel and iron using a three terminal capa... more Thermal expansion measurements have been performed on nickel and iron using a three terminal capacitance dilatometer with a new cell design and a theoretical model has been developed to obtain the electron-magnetic, lattice and magnon contributions to thermal expansion and corresponding Grüneisen parameters.

Research paper thumbnail of Thermal Expansion Study of Ordered and Disordered Fe3Al: An Effective Approach for the Determination of Vibrational Entropy

Physical Review Letters, 1996

Research paper thumbnail of Vibrational and Magnetic Contribution to Entropy of an L12 Ordered and a Partially Ordered Ni3Mn Alloy:. Results from Thermal Expansion Measurements and Model Calculations

International Journal of Modern Physics B, 1998

Thermal expansion measurements have been performed on an L12 ordered and a quenched Ni3Mn alloy a... more Thermal expansion measurements have been performed on an L12 ordered and a quenched Ni3Mn alloy and the role of electrons, phonons and magnetic moments on their thermodynamic properties has been studied using theoretical models. We show that with increasing atomic disorder the itinerant nature of the electron moments decreases. We furthermore show that magnetic interactions do not influence the chemical ordering of Ni3Mn, while lattice vibrations play an important role in its ordering transition.

Research paper thumbnail of Critical exponents of NiFeV alloys for the ferromagnetic–paramagnetic phase transition

Journal of Magnetism and Magnetic Materials, 2000

Research paper thumbnail of Critical exponents of NiFeV alloys for the ferromagnetic-paramagnetic phase transition

Journal of Magnetism and Magnetic Materials, 2000

A systematic study of the magnetic critical exponents has been made in Ni-rich NiFeV ternary allo... more A systematic study of the magnetic critical exponents has been made in Ni-rich NiFeV ternary alloys of compostions Ni 77Fe 7V 16, Ni 79Fe 5V 16 and Ni 78Fe 4V 18 in the critical region of ferromagnetic to paramagnetic (FM-PM) transition through detailed AC-susceptibiltiy and DC-magnetization measurements. In all the alloys, we have found a well-defined critical temperature TC below which the spontaneous magnetization increases with decreasing temperature. The critical exponents and critical amplitudes associated with the transitions are obtained. Their values show drastic changes from those of pure Ni.

Research paper thumbnail of High-pressure melting curve of helium and neon: Deviations from corresponding states theory

Research paper thumbnail of High-Pressure Melting Curve of Nitrogen and the Liquid-Liquid Phase Transition

Physical Review Letters, 2007

The melting curve of nitrogen was measured up to 71 GPa, a fourfold increase in pressure over pre... more The melting curve of nitrogen was measured up to 71 GPa, a fourfold increase in pressure over previous measurements. The measurements were made using the laser-heated diamond anvil cell and melting was detected in situ by the laser speckle method. The melting temperature rises linearly up to a maximum at 50 GPa and 1920 K, and with increasing pressure suddenly decreases linearly to 1400 K at 71 GPa. This sharp drop in the melting slope (dT/dP) above 50 GPa indicates the appearance of a liquid denser than the solid and of a liquid-liquid phase transition. The sharpness of the changes suggests that the transition is first order and is a liquid-liquid polymer transition. This conclusion is consistent with earlier theoretical studies and experimental evidence that pressure transforms molecular nitrogen into a chainlike polymeric form.

Research paper thumbnail of Mukherjee and Boehler Reply

Physical Review Letters, 2009

ABSTRACT A Reply to the Comment by E. Gregoryanz and A. F. Goncharov.

Research paper thumbnail of High pressure AC resistivity and compressibility study on Al 2(WO 4) 3

Journal of Physics and Chemistry of Solids, 2003

Research paper thumbnail of Reappearance of ferroelectric soft modes in the paraelectric phase of Pb1−xCaxTiO3 at high pressures: Raman and x-ray diffraction studies

Journal of Physics-condensed Matter, 2012

High pressure Raman spectroscopy and x-ray diffraction measurements have been carried out on Pb(1... more High pressure Raman spectroscopy and x-ray diffraction measurements have been carried out on Pb(1-x)Ca(x)TiO(3) (x = 0.10 and 0.30). Using high pressure Raman spectroscopic data, it is observed that the phonon instability responsible for the ferroelectric phase reappears in the paraelectric phase after a critical pressure. The observed critical pressures in the Ca(2+) doped PbTiO(3) system are much lower than the unique pressures suggested for PbTiO(3) based materials. A suitable explanation is given to explain this lowering of critical pressure. It is also shown that the ferroelectric phase which stabilizes in the paraelectric phase has a tetragonal symmetry with space group I4cm.

Research paper thumbnail of High pressure investigations of Na0.025WO3: x-ray diffraction and Raman spectroscopy studies

Journal of Physics-condensed Matter, 2011

High pressure x-ray diffraction and Raman spectroscopy studies have been carried out on non-stoic... more High pressure x-ray diffraction and Raman spectroscopy studies have been carried out on non-stoichiometric sodium tungsten bronze, Na0.025WO3. The high pressure investigations reveal a phase transition at about 2 GPa by a change of space group symmetry from P21/n to P21/c in the monoclinic cell followed by a second structural transformation to a triclinic lattice around 18 GPa. There are volume changes with these structural transformations, which are driven by rotation and significant distortion of WO6 octahedra due to the displacement of tungsten and oxygen atoms from their mean positions in the unit cell.

Research paper thumbnail of Effect of 0.18 at.% Re impurity on the Neel transition in chromium

Thermal expansion measurements are reported on Cr+0.18 at% Re alloy system near the Spin Density ... more Thermal expansion measurements are reported on Cr+0.18 at% Re alloy system near the Spin Density Wave transition at TN=318 K and incommensurate-commensurate transition at 297 K. The nature of the transition at TN is deduced to be weakly first order and a large change in anharmonicity is observed which implies a considerable lattice softening below TN.

Research paper thumbnail of Thermal expansion study of Bi2223 superconductor: an evidence of polaronic mechanism of high T c superconductivity with strong two-dimensional fluctuations

Physica C-superconductivity and Its Applications, 2000

Research paper thumbnail of Thermal Expansion of Alkali Halides:. a Semiclassical Model

Modern Physics Letters B, 1994

A simple-minded semiclassical method is used to obtain the thermal expansion of alkali halides vi... more A simple-minded semiclassical method is used to obtain the thermal expansion of alkali halides viz. KBr, KCl, Kl, and NaCl. It is observed that our theoretical prediction agrees fairly well with the available experimental data. It is furthermore suggested that the present method can be used for an accurate determination of the Debye temperature of alkali halides.

Research paper thumbnail of Anomalous thermal expansion behavior of the YBaCuO superconductor. Indirect evidence of polaron formation

Physica C-superconductivity and Its Applications, 1994

A simple-minded semiclassical method is used to study the thermal expansion data of YBa2Cu3O7-del... more A simple-minded semiclassical method is used to study the thermal expansion data of YBa2Cu3O7-delta (delta = 0.15) both in the normal and superconducting phases. It is shown that there is an anomaly in the temperature variation of the thermal expansion which begins to show up at a temperature somewhat higher than Tc. We argue that this anomaly can be attributed to the phenomenon of polaron formation. This might give an indirect support to the bipolaronic mechanism of high-temperature superconductivity.>

Research paper thumbnail of Thermal expansion analysis of Fe3-xMnxAl alloys

Physical Review B, 1998

ABSTRACT Thermal expansion measurements have been performed on the ternary alloy system, Fe3-xMnx... more ABSTRACT Thermal expansion measurements have been performed on the ternary alloy system, Fe3-xMnxAl for x=0.3, 0.9, and 1.2 to study the effect of Mn substitution on their thermal and magnetic properties. The vibrational and magnetic contributions to thermal expansion, specific heat, and entropy for these alloys have been determined using a theoretical model and various Grüneisen parameters have been obtained.

Research paper thumbnail of Effect of 0.18 at.% Re impurity on the Neel transition in chromium

ABSTRACT Thermal expansion measurements are reported on Cr+0.18 at% Re alloy syste... more ABSTRACT Thermal expansion measurements are reported on Cr+0.18 at% Re alloy system near the Spin Density Wave transition at TN=318 K and incommensurate-commensurate transition at 297 K. The nature of the transition at TN is deduced to be weakly first order and a large change in anharmonicity is observed which implies a considerable lattice softening below TN.

Research paper thumbnail of ElectronMagnetic, Lattice and Magnon Grüneisen Parameters of Iron and Nickel:. Results from Thermal Expansion Measurements and Model Calculations

International Journal of Modern Physics B, 1998

Thermal expansion measurements have been performed on nickel and iron using a three terminal capa... more Thermal expansion measurements have been performed on nickel and iron using a three terminal capacitance dilatometer with a new cell design and a theoretical model has been developed to obtain the electron-magnetic, lattice and magnon contributions to thermal expansion and corresponding Grüneisen parameters.

Research paper thumbnail of Thermal Expansion Study of Ordered and Disordered Fe3Al: An Effective Approach for the Determination of Vibrational Entropy

Physical Review Letters, 1996

Research paper thumbnail of Vibrational and Magnetic Contribution to Entropy of an L12 Ordered and a Partially Ordered Ni3Mn Alloy:. Results from Thermal Expansion Measurements and Model Calculations

International Journal of Modern Physics B, 1998

Thermal expansion measurements have been performed on an L12 ordered and a quenched Ni3Mn alloy a... more Thermal expansion measurements have been performed on an L12 ordered and a quenched Ni3Mn alloy and the role of electrons, phonons and magnetic moments on their thermodynamic properties has been studied using theoretical models. We show that with increasing atomic disorder the itinerant nature of the electron moments decreases. We furthermore show that magnetic interactions do not influence the chemical ordering of Ni3Mn, while lattice vibrations play an important role in its ordering transition.