S. Patnaik - School of Physical Sciences, Jawaharlal Nehru University

S. Patnaik
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Name
S. Patnaik
Affiliation
School of Physical Sciences, Jawaharlal Nehru University
City
New Delhi
Country
India

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Physics - Materials Science (25)
 
Physics - Superconductivity (23)
 
Physics - Strongly Correlated Electrons (22)
 
Mathematics - Operator Algebras (6)
 
Mathematics - Functional Analysis (5)
 
Physics - Mesoscopic Systems and Quantum Hall Effect (4)
 
Mathematics - Representation Theory (2)
 
Computer Science - Software Engineering (1)
 
Physics - Statistical Mechanics (1)
 
Physics - Other (1)
 
Quantum Physics (1)

Publications Authored By S. Patnaik

Incorporation of magnetism in graphene based compounds holds great promise for potential spintronic applications. By optimizing point defects and high edge density of defects, we report many-fold increase in the ferromagnetic saturation moment in lacey reduced graphene oxide nanoribbons (LRGONR) as compared to other graphene derivatives. The samples were synthesized using chemical unzipping methodology. Read More

SrxBi2Se3 is recently reported to be a superconductor derived from topological insulator Bi2Se3. It shows a maximum resistive Tc of 3.25 K at ambient pressure. Read More

Synthesis and extensive structural, pyroelectric, magnetic, dielectric and magneto-electric characterizations are reported for polycrystalline Co4Nb2O9 towards unraveling the multiferroic state especially in reference to the magnetic spin flop transition. Magnetic measurements confirm the Co4Nb2O9 becomes antiferromagnetic (AFM) at around 28 K but no clear evidence for spin-flop effect was found. Associated with the magnetic phase transition, a sharp peak in pyroelectric current indicates the appearance of the strong magneto-electric coupling below Neel temperature (TN) with a large coupling constant upto 17. Read More

We report synthesis, structural details and electrical transport properties of topological insulator Bi2Te3. The single crystalline specimens of Bi2Te3 are obtained from high temperature (950C) melt and slow cooling (2C/hour). The resultant crystals were shiny, one piece (few cm) and of bright silver color. Read More

We report a study on a series of lanthanum doped barium stannate-titanate (LBTS) ceramics towards correlating their microstructure with ferroelectric properties. The samples were prepared by solid state reaction technique and the XRD analysis indicated predominantly single phase microstructure. Scanning Electron Microscopy revealed that while a low La doping of 1 atomic % yielded inhibited grain growth in 1LBTS, higher amounts of La doping yield larger leafy grains. Read More

We report a detailed magneto-transport study in single crystals of NbP. High quality crystals were grown by vapour transport method. An exceptionally large magnetoresistance is confirmed at low temperature which is non-saturating and is linear at high fields. Read More

We report flux free growth of superconducting FeSe single crystals by an easy and versatile high temperature melt and slow cooling method for first time. The room temperature XRD on the surface of the piece of such obtained crystals showed single 101 plane of Beta-FeSe tetragonal phase. The bulk powder XRD, being obtained by crushing the part of crystal chunk showed majority tetragonal and minority FeSe hexagonal crystalline phases. Read More

We consider a quantum self-contained fridge consisting of three qubits interacting with three separate heat reservoirs, respectively, and functioning without any external controls. Applying the methods of endoreversible thermodynamics, we derive explicit expressions of cooling load versus efficiency of this fridge, which demonstrate behaviors of trade-off between those two quantities and thus enable to discuss the thermoeconomic optimization of performance. We also discuss a possibility for the amplification of cooling load briefly in a simple modification from the original architecture of fridge. Read More

We report synthesis of non-centrosymmetric BiPd single crystal by self flux method. The BiPd single crystal is crystallized in monoclinic structure with the P21 space group. Detailed SEM (Scanning Electron Microscopy) results show that the crystals are formed in slab like morphology with homogenous distribution of Bi and Pd. Read More

We report on two fold increase in superconducting transition temperature of La3Co4Sn13 by substituting indium at the tin site. The transition temperature of this skutterudite is observed to increase from 2.5 K to 5. Read More

Strontium intercalation between van der Waals bonded layers of topological insulator Bi2Se3 is found to induce superconductivity with a maximum Tc of 2.9 K. Transport measurement on single crystal of optimally doped sample Sr0. Read More

Superconducting order parameter and its symmetry are important parameters towards deciphering the pairing mechanism in newly discovered superconducting systems. We report a study on penetration depth measurement on Nb2PdS5 that has recently been reported with extremely high upper critical field with possible triplet pairing mechanism. Our data show that at low temperatures the change in penetration depth is best fitted with BCS s-wave model for single gap. Read More

We report on the impact of hydrostatic pressure on the superconductivity of optimally (Indium) doped SnTe which is established to be derived from a topological crystalline insulating phase. Single crystals of Sn1-xInxTe were synthesized by a modified Bridgman method that exhibited maximum superconducting Tc of 4.4 K for x= 0. Read More

2014Dec
Affiliations: 1Department of Physics, Indian Institute of Technology, 2Department of Physics, Indian Institute of Technology, 3Department of Physics, Banaras Hindu University, 4Department of Physical Sciences, School of Chemical and Physical Sciences, Sikkim University, 5Department of Physical Sciences, School of Chemical and Physical Sciences, Sikkim University, 6School of Physical Sciences, Jawaharlal Nehru University, 7School of Physical Sciences, Jawaharlal Nehru University, 8Department of Physics, Banaras Hindu University, 9Department of Physics, Indian Institute of Technology

The structural, magnetic, electrical and transport properties of FeV2O4, by doping Li and Cr ions respectively in A and B sites, have been studied. Dilution of A-site by Li doping increases the ferri-magnetic ordering temperature and decreases the ferroelectric transition temperature. This also decreases the V-V distances which in effect increases the A-V coupling. Read More

Cu3Nb2O8 is an unusual multiferroic compound that undergoes a series of magnetic ordering at low temperatures. Concurrent development of electric polarization has been reported at TN1 ~25 K corresponding to a non-collinear helicoidal ordering (Phys. Rev. Read More

Denote by $U_{\mathcal I}({\mathcal H})$ the group of all unitary operators in ${\bf 1}+{\mathcal I}$ where ${\mathcal H}$ is a separable infinite-dimensional complex Hilbert space and ${\mathcal I}$ is any two-sided ideal of ${\mathcal B}({\mathcal H})$. A Cartan subalgebra ${\mathcal C}$ of ${\mathcal I}$ is defined in this paper as a maximal abelian self-adjoint subalgebra of~${\mathcal I}$ and its conjugacy class is defined herein as the set of Cartan subalgebras $\{V{\mathcal C} V^*\mid V\in U_{\mathcal I}({\mathcal H})\}$. For nonzero proper ideals ${\mathcal I}$ we construct an uncountable family of Cartan subalgebras of ${\mathcal I}$ with distinct conjugacy classes. Read More

We report on the superconducting properties of In doped SnTe which has recently been explored as a topological crystalline superconductor. Single crystals of Sn0.5In0. Read More

Coexistence of mutually influencing ferroelectric and magnetic ordering at low temperature in hexagonal phase of rare-earth manganites gives rise to interesting physical phenomena. Here, we report a detailed analysis of powder neutron diffraction (ND) studies on polycrystalline Y1-xDyxMnO3 (x = 0, 0.05) as a function of temperature. Read More

The objective of this research work is to improve the degree of excellence by removing the number of exceptions from the software. The modern age is more concerned with the quality of software. Extensive research is being carried out in this direction. Read More

We report on the magnetic entropy change and the critical exponents in the double perovskite manganite Y2NiMnO6 with a ferromagnetic to paramagnetic transition TC=85K. For a magnetic field change of 80kOe, a maximum magnetic entropy change -6.57 J /kg K is recorded around TC. Read More

We report NdCrTiO5 to be an unusual multiferroic material with large magnetic field dependent electric polarization. While magneto-electric coupling in this two magnetic sub-lattice oxide is well established, the purpose of this study is to look for spontaneous symmetry breaking at the magnetic transition. The conclusions are based on extensive magnetization, dielectric and polarization measurements around its antiferromagnetic ordering temperature of 18K. Read More

We report observation of magneto-electric and magneto-dielectric couplings in ceramic Co3TeO6. Temperature dependent DC magnetization and dielectric constant measurements together indicate coupling between magnetic order and electronic polarization. Strong anomaly in dielectric constant at ~ 18K in zero magnetic field indicates presence of spontaneous polarization. Read More

We report on the superconducting gap and pairing symmetry in layered superconductor Bi4O4S3. The measurement of temperature dependence of magnetic penetration depth was carried out using tunnel diode oscillator technique. It is observed that Bi4O4S3 is a conventional s-wave type superconductor with fully developed gap. Read More

We have systematically studied the substitution of nonmagnetic Zn and magnetic Ni at iron sites in Ce based oxypnictide. The parent compound (CeOFeAs) shows an anomaly in resistivity around 150 K due to structural transition from tetragonal (space group: P4/nmm) to orthorhombic structure (space group: Cmma). Substitution of Zn suppresses this anomaly to lower temperature (~130 K) but Ni substitution does not show any anomaly around this temperature and the compound behaves like a metal. Read More

We report on the synthesis and extensive characterization of layered Bi4O4S3 superconductor. This is the optimally doped sample with Tc ~5.3 K out of a series of Bi6O4S4(SO4)_1-x samples synthesized by solid state reaction. Read More

We report multiferroic behavior in double perovskite Y2CoMnO6 with ferroelectric transition temperature Tc = 80K. The origin of ferroelectricity is associated with magnetic ordering of Co2+ and Mn4+ moments in a up-up-down-down arrangement. The saturation polarization and magnetization are estimated to be 65 uC/m2 and 6. Read More

Operator ideals in B(H) are well understood and exploited but ideals inside them have only recently been studied starting with the 1983 seminal work of Fong and Radjavi and continuing with two recent articles by the authors of this survey. This article surveys this study embodied in these three articles. A subideal is a two-sided ideal of J (for specificity also called a J-ideal) for J an arbitrary ideal of B(H). Read More

In the framework of operator theory, we investigate a close Lie theoretic relationship between all operator ideals and certain classical groups of invertible operators that can be described as the solution sets of certain algebraic equations, hence can be regarded as infinite-dimensional linear algebraic groups. Historically, this has already been done for only the complete-norm ideals; in that case one can work within the framework of the well-known Lie theory for Banach-Lie groups. That kind of Lie theory is not applicable for arbitrary operator ideals, so we needed to find a new approach for dealing with the general situation. Read More

A sequel to \cite{gW05}, we address again the single commutator problem \cite{PT71} of Pearcy and Topping: Is every compact operator a single commutator of compact operators? by focusing on a 35 year old test question for this posed in 1976 by the last named author and others: Are there any strictly positive operators that are single commutators of compact operators? The latter we settle here affirmatively with a modest modification of Anderson's fundamental construction \cite{jA77} constructing compact operators whose commutator is a rank one projection. Moreover we provide here a rich class of such strictly positive operators that are commutators of compact operators and pose a question for the rest. We explain also how these methods are related to the study of staircase matrix forms, their equivalent block tri-diagonal forms, and commutator problems. Read More

A subideal is an ideal of an ideal of B(H) and a principal subideal is a principal ideal of an ideal of B(H). We determine necessary and sufficient conditions for a principal subideal to be an ideal of B(H). This generalizes to arbitrary ideals the 1983 work of Fong and Radjavi characterizing principal subideals of the ideal of compact operators that are also ideals of B(H). Read More

A subideal (also called a J-ideal) is an ideal of a B(H)-ideal J. This paper is the sequel to Subideals of operators where a complete characterization of principal and then finitely generated J-ideals were obtained by first generalizing the 1983 work of Fong and Radjavi who determined which principal K(H)-ideals are also B(H)-ideals. Here we determine which countably generated J-ideals are B(H)-ideals, and in the absence of the continuum hypothesis which J-ideals with generating sets of cardinality less than the continuum are B(H)-ideals. Read More

We report here synthesis, structural, DC magnetization, and transport studies of new BiS2 based layered LaO0.5F0.5BiS2 superconductor [1]. Read More

Very recent report [1] on observation of superconductivity in Bi4O4S3 could potentially reignite the search for superconductivity in a broad range of layered sulphides. We report here synthesis of Bi4O4S3 at 5000C by vacuum encapsulation technique and basic characterizations. Detailed structural, magnetization, and electrical transport results are reported. Read More

Hexagonal YMnO_3 with space group P63cm is one of the rare examples of multiferroic materials that exhibit co-dependence of a robust ferroelectric phase along with antiferromagnetic ordering. This is primarily ascribed to tilting of the MnO_5 polyhedra driven by magnetoelectric coupling. We report on the effect of magnetic field at the atomic level in YMnO_3 by utilizing magnetic field and temperature dependent neutron diffraction measurements. Read More

We report interesting anomalies in the temperature dependent Raman spectra of FeSe$_{0.82}$ measured from 3K to 300K in the spectral range from 60 to 1800 cm$^{-1}$ and determine their origin using complementary first-principles density functional calculations. A phonon mode near 100 cm$^{-1}$ exhibits a sharp increase by $\sim$ 5% in frequency below a temperature T$_s$ ($\sim$ 100 K) attributed to strong spin-phonon coupling and onset of short-range antiferromagnetic order. Read More

We report significant enhancement in superconducting properties of yttrium substituted Ce1-xYxOFFeAs superconductors. The polycrystalline samples were prepared by two step solid state reaction technique. X-ray diffraction confirmed tetragonal ZrCuSiAs structure with decrease in both a and c lattice parameters on increasing yttrium substitution (with fixed F content). Read More

We report the synthesis of cobalt nanoparticles with different shapes and sizes by rapid pyrolysis of cobalt carbonyl in the presence of various surfactants. The size and shape of the nanoparticles were influenced by reaction conditions, such as type of the surfactant, molar ratio of surfactant to precursor, reflux temperature and reaction time. The shapes that we have achieved include spherical, nearly spherical, disc and cube. Read More

We report on the preparation of ferromagnetic cobalt nanospheres with antiferromagnetic oxide capping layer and its implication for the variation in magnetic property. The hcp cobalt nanospheres were prepared by thermal decomposition of cobalt carbonyl in the presence of organic surfactants. The spherical nanoparticles thus prepared were oxidized to grow antiferromagnetic layers of varying composition and thickness on top of cobalt spheres. Read More

We report synthesis of phase pure multiferroic YMnO3 thin films on sapphire (0001)with conducting ZnGaO buffer contact layer. Films were prepared by using pulsed laser deposition technique and characterized using x-ray diffraction(XRD), Scanning electron microscopy (SEM), Energy dispersive absorption spectroscopy (EDAX) and magnetic field dependent dielectric measurement techniques. Structural characterizations indicated phase purity and epitaxial nature of the films. Read More

The geometrically frustrated magnet Ni3V2O8 undergoes a series of competing magnetic ordering at low temperatures. Most importantly, one of the incommensurate phases has been reported to develop a ferroelectric correlation caused by spin frustration. Here we report an extensive thermodynamic, dielectric and magnetic study on clean polycrystalline samples of this novel multiferroic compound. Read More

Electron-doping of the semimetal (CeOFeAs) by either fluorine (max Tc ~ 43 K)or cobalt (max Tc ~ 11 K) leads to superconductivity. Here we show the effect of transition metal (Co) substitution at the iron site on the superconducting properties of CeO0.9F0. Read More

Magnetization, magnetoresistance, and magnetodielectric measurements have been carried out on the half doped charge ordered manganite, Pr_0.5Ca_0.5MnO_3. Read More

We report the synthesis and characterization of a new electron-doped La-oxypnictide superconductor by partial substitution of lanthanum by thorium. The superconducting transition temperature at about 30.3 K was observed in La0. Read More

Bulk dc resistivity and dielectric constant measurements with temperature and frequency have been performed in LaMn_{1-x}Fe_xO_3 (0 <= x <= 1.0) as a result of Fe substitution both for the as-synthesized and oxygen annealed samples. Temperature dependence of real part of dielectric constant at different frequencies show a frequency and temperature independent value (epsilon_s) at low temperature for x >= 0. Read More

We have successfully synthesized Ce based oxypnictide with fluorine doping (CeO_{1-x}F_xFeAs) by a two step solid state reaction method. Detailed XRD and EDX confirm the crystal structure and chemical compositions. We observe that an extremely high Hc2(0) of 94 T can be achieved in the x = 0. Read More

Pure phases of a new oxyarsenide superconductor of the nominal composition CeOFe0.9Co0.1As was successfully synthesized by solid state reaction in sealed silica ampoules at 1180 C. Read More

We describe a new methodology of synthesizing the oxypnictide superconductors with potassium fluoride as a source as a source of fluorine instead of LaF3. This route also allows the substitution of potassium at lanthanum sites which leads to an increase in the upper critical field as would be expected for a multiband superconductor. We also report the highest reported Tc onset of 28. Read More

The dissipative mechanism at low current density is compared in three different classes of superconductors. This is achieved by measurement of resistance as a function of temperature and magnetic field in clean polycrystalline samples of NbSe2, MgB2 and Bi2Sr2Ca2Cu3O10 superconductors. Thermally activated flux flow behavior is clearly identified in bulk MgB2. Read More

We report remarkable multiferroic effects in polycrystalline Bi2Fe4O9. High-resolution X-ray diffraction shows that this compound has orthorhombic structure. Magnetic measurements confirm an antiferromagnetic transition around 260 K. Read More