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Mukul Gupta

Bio: Mukul Gupta is an academic researcher from Indian Department of Atomic Energy. The author has contributed to research in topics: Thin film & Materials science. The author has an hindex of 26, co-authored 278 publications receiving 2519 citations. Previous affiliations of Mukul Gupta include ETH Zurich & High Energy Materials Research Laboratory.


Papers
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Journal ArticleDOI
01 Nov 2008-Pramana
TL;DR: In this article, the authors describe the design, construction and performance of a new high resolution neutron powder diffractometer that has been installed at the Dhruva reactor, Trombay, India.
Abstract: In this paper, we describe the design, construction and performance of a new high resolution neutron powder diffractometer that has been installed at the Dhruva reactor, Trombay, India. The instrument employs novel design concepts like the use of bent, perfect crystal monochromator and open beam geometry, enabling the use of smaller samples. The resolution curve of the instrument was found to have little variation over a wide angular region and a Δd/d ∼ 0.3% has been achieved. The instrument provides sample environment of very low temperatures and high magnetic fields using a 7 Tesla cryogen-free superconducting magnet with a VTI having a temperature range of 1.5–320 K. The special sample environment and high resolution make this neutron powder diffractometer a very powerful facility for studying magnetic properties of materials.

81 citations

Proceedings ArticleDOI
TL;DR: In this article, a soft x-ray beamline on a bending magnet source of Indus-2 storage ring (2.5 GeV) was developed and the beamline layout is based on a spherical grating monochromator.
Abstract: This article describes the development of a soft x-ray beamline on a bending magnet source of Indus-2 storage ring (2.5 GeV) and some preliminary results of x-ray absorption spectroscopy (XAS) measurements using the same. The beamline layout is based on a spherical grating monochromator. The beamline is able to accept synchrotron radiation from the bending magnet port BL-1 of the Indus-2 ring with a wide solid angle. The large horizontal and vertical angular acceptance contributes to high photon flux and selective polarization respectively. The complete beamline is tested for ultrahigh vacuum (UHV) ∼ 10−10 mbar. First absorption spectrum was obtained on HOPG graphite foil. Our performance test indicates that modest resolving power has been achieved with adequate photon flux to carry out various absorption experiments.

61 citations

Journal ArticleDOI
TL;DR: In this article, a mechanism inducing nanocrystallization and amorphization in Fe and NiFe due to reactive nitrogen sputtering is discussed, and the surface, structural, and magnetic properties of the deposited films were studied using x-ray reflection and diffraction, transmission electron microscopy, polarized neutron reflectivity, and using a dc extraction magnetometer.
Abstract: Thin films of iron and permalloy $({\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20})$ were prepared using an $\mathrm{Ar}+{\mathrm{N}}_{2}$ mixture with a magnetron sputtering technique at ambient temperature. The nitrogen partial pressure during the sputtering process was varied in the range of $0\ensuremath{\leqslant}{R}_{{\mathrm{N}}_{2}}\ensuremath{\leqslant}100%$, keeping the total gas flow at constant. At lower nitrogen pressures $({R}_{{\mathrm{N}}_{2}}\ensuremath{\leqslant}33%)$, both Fe and NiFe first form a nanocrystalline structure, and an increase in ${R}_{{\mathrm{N}}_{2}}$ results in the formation of an amorphous structure. At intermediate nitrogen partial pressures, nitrides of Fe and NiFe were obtained, while at even higher nitrogen partial pressures, nitrides themselves became nanocrystalline or amorphous. The surface, structural, and magnetic properties of the deposited films were studied using x-ray reflection and diffraction, transmission electron microscopy, polarized neutron reflectivity, and using a dc extraction magnetometer. The growth behavior for amorphous film was found to be different as compared with poly or nanocrystalline films. The soft-magnetic properties of FeN were improved on nanocrystallization, while those of NiFeN were degraded. A mechanism inducing nanocrystallization and amorphization in Fe and NiFe due to reactive nitrogen sputtering is discussed in the present article.

56 citations

Journal ArticleDOI
Mukul Gupta1, Thomas Gutberlet1, Jochen Stahn1, P. Keller1, D. Clemens1 
01 Jul 2004-Pramana
TL;DR: The AMOR as mentioned in this paper was designed to perform reflectometry measurements in horizontal sample-plane geometry, which allows studying both solid-liquid and liquid-liquid interfaces using a pulsed cold neutron beam from the end position of the neutron guide.
Abstract: The apparatus for multioptional reflectometry (AMOR) at SINQ/PSI is a versatile reflectometer operational in the time-of-flight (TOF) mode (in a wavelength range of 0.15 nm < λ < 1.3 nm) as well as in the monochromatic (θ- 2θ) mode with both polarized and unpolarized neutrons. AMOR is designed to perform reflectometry measurements in horizontal sample-plane geometry which allows studying both solid-liquid and liquid-liquid interfaces. A pulsed cold neutron beam from the end position of the neutron guide is produced by a dual-chopper system (side-by-side) having two windows at 180‡ and rotatable with a maximum frequency of 200 Hz. In the TOF mode, the chopper frequency, width of the gating window and the chopper-detector distance can be selected independently providing a wide range of q-resolution (Δq/q = 1–10%). Remanent FeCoV/Ti:N supermirrors are used as polarizer/analyzer with a polarization efficiency of ∼97%. For the monochromatic wavelength mode, a Ni/Ti multilayer is used as a monochromator, giving ∼50% reflectivity at a wavelength of 0.47 nm. In the present work, a detailed description of the instrument and setting-up of the polarization option is described. Results from some of the recent studies with polarized neutrons and measurements on liquid surfaces are presented.

55 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of growth temperature on the optical properties of TiO2 thin films of widely different structural and morphological characteristics were grown on Si (1.0) substrates using ALD by varying the substrate temperature (Ts) in a wide range (50 −°C −≤ −Ts −400°C).

55 citations


Cited by
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Journal ArticleDOI
01 Apr 1988-Nature
TL;DR: In this paper, a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) is presented.
Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

9,929 citations

Journal ArticleDOI
01 Mar 1906-Nature
TL;DR: In view of the interest attaching to the vaporisation and diffusion of solids, the following observations may be worthy of record as discussed by the authors, which may be seen as a good starting point for further research.
Abstract: IN view of the interest attaching to the vaporisation and diffusion of solids, the following observations may be worthy of record.

560 citations

Journal Article
TL;DR: In this article, the authors describe vector measurements of the current-induced effective field in Ta|CoFeB|MgO heterostructures and show that the effective field exhibits a significant dependence on the Ta and CoFeB layer thicknesses.
Abstract: Current-induced effective magnetic fields can provide efficient ways of electrically manipulating the magnetization of ultrathin magnetic heterostructures. Two effects, known as the Rashba spin orbit field and the spin Hall spin torque, have been reported to be responsible for the generation of the effective field. However, a quantitative understanding of the effective field, including its direction with respect to the current flow, is lacking. Here we describe vector measurements of the current-induced effective field in Ta|CoFeB|MgO heterostructrures. The effective field exhibits a significant dependence on the Ta and CoFeB layer thicknesses. In particular, a 1 nm thickness variation of the Ta layer can change the magnitude of the effective field by nearly two orders of magnitude. Moreover, its sign changes when the Ta layer thickness is reduced, indicating that there are two competing effects contributing to it. Our results illustrate that the presence of atomically thin metals can profoundly change the landscape for controlling magnetic moments in magnetic heterostructures electrically.

540 citations