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P. Mohanty

Publications and source records attributed to P. Mohanty.

At least 19 recordsLinked to original sources
arXiv2026

Nuclear Structure and Shape Evolution of Nd Isotopes

In this work, we have analyzed the structural properties of even-even $^{126-188}Nd_{60}$ isotopes. For this we have used axially deformed Relativistic Mean Field (RMF) model with PK1 and NL-SH parametrization. In structural properties, We have estimated and analyzed binding energy per nucleon (B.E./A), two neutron separation energy ($S_{2n}$), differential variation of two neutron separation energy ($dS_{2n}$), quadrupole deformation parameter ($β_{2}$), root mean square nuclear charge radius ($r_{ch}$), neutron skin thickness ($r_{np}$) and single particle energy (SPE) levels of Nd isotopes. Some bulk properties are also compared with experimentally accessible results and with results of Finite Range Droplet Model (FRDM). To understand the shape evolution around N = 92, the variation of the potential energy curves (PECs) with quadrupole deformation parameter are also investigated. From all the investigations, We observe some sign of stability at N = 92 and shape transitions around it.

nucl-th↗
arXiv2023

Room Temperature Ferrimagnetism, Magnetodielectric and Exchange Bias Effect in CoFeRhO$_4$

Geometrically frustrated structures combined with competing exchange interactions that have different magnitudes are known ingredients for achieving exotic properties. Herein, we studied detailed structural, magnetic, thermal (specific heat), magneto-dielectric, and magnetic exchange bias properties of a mixed 3d - 4d spinel oxide with composition CoFeRhO$_4$. Detailed magnetization, heat capacity, and neutron powder diffraction studies (NPD) highlight long-range ferrimagnetic ordering with an onset at 355 K. The magnetic structure is established using a ferrimagnetic model (collinear-type) that has a propagation vector k = 0, 0, 0. The magneto-dielectric effect appears below the magnetic ordering temperature, and the exchange bias (EB) effect is observed in field cooled (FC) conditions below 355 K. The magneto-dielectric coupling in CoFeRhO$_4$ originates due to the frustration in the structure, collinear ferrimagnetic ordering, and uncompensated magnetic moments. The unidirectional anisotropy resulting from the uncompensated magnetic moments causes the room-temperature exchange bias effect. Remarkably, the appearance of technologically important properties (ferromagnetism, magnetodielectric effect, and EB) at room temperature in CoFeRhO$_4$ indicates its potential use in sensors or spintronics.

cond-mat.mtrl-sci↗
arXiv2021

Impact of Cr doping on the structure, optical and magnetic properties of nanocrystalline ZnO particles

The role of Cr incorporation into the ZnO were probed through investigations into the structural, optical and magnetic properties. Zn1-xCrxO with x = 0, 0.01, 0.03 and 0.05, nanoparticles were prepared by solution combustion method. Powder x-ray diffraction (XRD) results reveal, all the synthesized samples are in single hexagonal wurtzite crystal structures, indicating that Cr3+ ions substitute the Zn2+ ions without altering the structure. The crystallite size and microstrain were calculated using the Willamson-Hall method and found to be 36 +- 2 nm for ZnO and it reduced with the increase of Cr dopant concentration to 20 +- 2 nm for Zn0.95Cr0.05O. Transmission electron microscopy (TEM) revealed that the particle size were 48 +- 2 nm, 29 +- 2 nm and 25 +- 2 nm for the Zn1-xCrxO with x = 0, 0.03 and 0.05, respectively. TEM morphology indicated particles are agglomerated in the doped samples. The band-gap decreases slightly from 3.305 +- 0.003 eV to 3.292 +- 0.003 eV with increase of Cr content from x = 0 to 0.05, respectively. Photoluminescence measurements revealed the presence of defects in the samples, associated with zinc vacancies and singly ionized oxygen vacancy. The field-dependent magnetization measurements of ZnO and Cr-doped ZnO were carried out using a vibrating sample magnetometer (VSM) at 300 K. All the samples exhibits ferromagnetic behavior. This long-range ferromagnetism ordering observed in ZnO is explained based on bound magnetic polaron (BMP) mechanism. The singly ionized oxygen vacancies playing a crucial role in observed room temperature ferromagnetism (RTFM) in ZnO. There is a sufficient amount of BMPs formed in Cr doped ZnO because of the defects present in these samples. Therefore, the overlapping of BMPs results in the RTFM. However, the antiferromagnetic coupling at a higher doping concentration of Cr, weakens the observed RTFM.

cond-mat.mtrl-sci↗
arXiv2021

Structure, optical and magnetic properties of Fe doped, Fe+Cr co-doped ZnO nanoparticles

The study particularly focuses on the effect of the Cr co-doping on the structural, optical and magnetic properties of Zn0.99Fe0.01O. Zn0.99-xFe0.01CrxO (x =0, 0.01, 0.03 and 0.05) nanoparticles. Powder x-ray diffraction (XRD) analysis confirms all the samples have hexagonal wurtzite structures. The average crystallite size (D) and microstrain of the samples were calculated using the Williamson-Hall relation and D was found to be 13 +- 1 nm for Zn0.99Fe0.01O. In Cr co-doped samples, D increase slightly with Cr content and are given by 9 +- 1, 10 +- 1, and 11 +- 1 nm for the samples with x = 0.01, 0.03 and 0.05, respectively; while the strain decreased with increase in Cr co-doping. Transmission electron microscopy (TEM) images of the samples indicate that particles are in the nano-regime and agglomerated. Particle sizes are found to be 14 +- 1, 11 +- 1 and 12 +- 1 nm for Zn0.99-xFe0.01CrxO with x = 0, 0.03 and 0.05, respectively. The substitution of Fe3+ and Cr3+ at Zn2+ sites has an impact on the optical properties. The band-gap decreases from 3.296 +- 0.002 eV to 3.258 +- 0.002 eV with increase of Cr concentration. Photoluminescence (PL) of Zn0.96Fe0.01Cr0.03O revealed the presence of defects, the emission peaks at 410 nm and 513 nm are attributed to Zn vacancies (VZn) and singly ionized oxygen vacancies, respectively. The M(-H) curves of Zn0.99-xFe0.01CrxO (x = 0.03 and 0.05) measured at room temperature using a vibrating sample magnetometer (VSM) are found to be hysteretic, signifying room temperature ferromagnetism (RTFM). Maximum saturation magnetization, 0.67 +- 0.01 emu.g-1, is observed in Zn0.94Fe0.01Cr0.05O. The observed RTFM in Fe+Cr co-doped ZnO is explained by of bound magnetic polaron (BMP) mechanism, the BMPs are formed by VZn and Vo^+ defects. This paper enhances the understanding of the origin of RTFM in Fe+Cr co-doped ZnO nanoparticles.

cond-mat.mtrl-sci↗
arXiv2019

Role of Ni substitution on structural, magnetic and electronic properties of epitaxial CoCr2O4 spinel thin films

Cubic spinel CoCr2O4 has attained recent attention due to its multiferroic properties. However, the Co site substitution effect on the structural and magnetic properties has rarely been studied in thin film form. In this work, the structural and magnetic properties of Co1-xNixCr2O4 (x = 0, 0.5) epitaxial thin films deposited on MgAl2O4 (100) and MgO (100) substrates to manipulate the nature of strain in the films using pulsed laser deposition (PLD) technique are presented. The epitaxial nature of the films was confirmed through X-ray diffraction (XRD) and Rutherford backscattering spectrometry (RBS) measurements. Raman measurements revealed a disappearance of characteristic A1g and F2g modes of the CoCr2O4 with increase in the Ni content. Atomic force microscopy (AFM) studies show a modification of the surface morphology upon Ni substitution. Magnetic measurements disclose that the ferrimagnetic Curie temperature (Tc) of the CoCr2O4 in thin film grown on MgAl2O4 (100) and MgO (100) substrates were found to be 100.6 +/- 0.5 K and 93.8 +/- 0.2 K, respectively. With Ni substitution the transition temperatures significantly get enhanced from that of CoCr2O4. X-ray photoelectron spectroscopy (XPS) suggests Cr3+ oxidation states in the films, while Co ions are present in a mixed Co2+/Co3+ oxidation state. The substitution of Ni at Co site significantly modifies the line shape of the core level as well as the valence band. Ni ions are also found to be in a mixed 2+/3+ oxidation state. O 1s core level display asymmetry related to possible defects like oxygen vacancies in the films.

cond-mat.mtrl-sci↗
arXiv2016

Phase Cascade Bridge Rectifier Array in a 2-D lattice

We report on a novel rectification phenomenon in a 2-D lattice network consisting of $N\times N$ sites with diode and AC source elements with controllable phases. A phase cascade configuration is described in which the current ripple in a load resistor goes to zero in the large $N$ limit, enhancing the rectification efficiency without requiring any external capacitor or inductor based filters. The integrated modular configuration is qualitatively different from conventional rectenna arrays in which the source, rectifier and filter systems are physically disjoint. Exact analytical results derived using idealized diodes are compared to a realistic simulation of commercially available diodes. Our results on nonlinear networks of source-rectifier arrays are potentially of interest to a fast evolving field of distributed power networks.

physics.class-ph↗
arXiv2009

Arbitrary distribution and nonlinear modal interaction in coupled nanomechanical resonators

We propose a general one-dimensional {\em continuous} formulation to analyze the vibrational modes of antenna-like nanomechanical resonators consisting of two symmetric arrays of cantilevers affixed to a central nano-beam. The cantilever arrays can have arbitrary density and length profile along the beam. We obtain the secular equation that allows for the determination of their frequency spectrum and illustrate the results on the particular examples of structures with constant or alternating cantilever length profiles. We show that our analytical results capture the vibration spectrum of such resonators and elucidate key relationships that could prove advantageous for experimental device performance. Furthermore, using a perturbative approach to treat the nonlinear and dissipative dynamics of driven structures, we analyze the anharmonic coupling between two specific widely spaced modes of the coupled-element device, with direct application to experiments.

math-ph↗
arXiv2008

Model of response spectrum and modal interaction in coupled nanomechanical resonators

We develop a simple continuum model to analyze the vibrational modes of a nanomechanical multi-element structure. In this model, arrays of sub-micron cantilevers located symmetrically on both sides of the central clamped-clamped nanobeam are replaced by a continuum. In this approach, the punctual shear forces exerted by the cantilevers on the central beam are smoothed out and the equations of motion of the structure become exactly solvable. Our analytical results capture the main features of the vibrational modes observed both numerically and experimentally. Furthermore, using a perturbative approach to treat the nonlinear dynamics of the structure, we establish its frequency-amplitude response and analyze the mechanism of anharmonic coupling between two specific widely spaced modes of the resonator.

cond-mat.mes-hall↗
arXiv2006

Coherent Signal Amplification in Bistable Nanomechanical Oscillators by Stochastic Resonance

Stochastic resonance is a counter-intuitive concept[1,2], ; the addition of noise to a noisy system induces coherent amplification of its response. First suggested as a mechanism for the cyclic recurrence of ice ages, stochastic resonance has been seen in a wide variety of macroscopic physical systems: bistable ring lasers[3], SQUIDs[4,5], magnetoelastic ribbons[6], and neurophysiological systems such as the receptors in crickets[7] and crayfish[8]. Although it is fundamentally important as a mechanism of coherent signal amplification, stochastic resonance is yet to be observed in nanoscale systems. Here we report the observation of stochastic resonance in bistable nanomechanical silicon oscillators, which can play an important role in the realization of controllable high-speed nanomechanical memory cells. Our nanomechanical systems were excited into a dynamic bistable state and modulated in order to induce controllable switching; the addition of white noise showed a marked amplification of the signal strength. Stochastic resonance in nanomechanical systems paves the way for exploring macroscopic quantum coherence and tunneling, and controlling nanoscale quantum systems for their eventual use as robust quantum logic devices.

cond-mat.mes-hall↗
arXiv2006

Signal Processing and Control in Nonlinear Nanomechanical Systems

Bestriding the realms of classical and quantum mechanics, nanomechanical structures offer great promise for a huge variety of applications, from computer memory elements \cite{badzey04} and ultra-fast sensors to quantum computing. Intriguing as these possibilities are, there still remain many important hurdles to overcome before nanomechanical structures approach anything close to their full potential. With their high surface-to-volume ratios and sub-micron dimensions, nanomechanical structures are strongly affected by processing irregularities and susceptible to nonlinear effects. There are several ways of dealing with nonlinearity: exceptional fabrication process control in order to minimize the onset of nonlinear effects or taking advantage of the interesting and oftentimes counterintuitive consequences of nonlinearity. Here, we present evidence for the use of stochastic resonance as a means of coherent signal amplification for use in nanomechanical devices. Aside from being simply one more system in which the phenomenon has been demonstrated, nanoscale systems \cite{lee03} are interesting because of their proximity to the realm of quantum mechanics. The combination of stochastic resonance and quantum mechanics has been the subject of intense theoretical activities \cite{wellens00, goychuk99, grif96, lof94} for many years; nanomechanical systems present a fertile ground for the study of a broad variety of novel phenomena in quantum stochastic resonance. Additionally, the physical realization of such nonlinear nanomechanical strings offer the possibility of studying a whole class of phase transition phenomena, particularly those modeled by a Landau-Ginzburg quantum string \cite{benzi85, hu99}.

cond-mat.mes-hall↗
arXiv2005

A Spin-Mechanical Device for Detection and Control of Spin Current by Nanomechanical Torque

We propose a spin-mechanical device to control and detect spin currents by mechanical torque. Our hybrid nano-electro-mechanical device, which contains a nanowire with a ferromagnetic-nonmagnetic interface, is designed to measure or induce spin polarized currents. Since spin carries angular momentum, a spin flip or spin transfer process involves a change in angular momentum--and hence, a torque--which enables mechanical measurement of spin flips. Conversely, an applied torque can result in spin polarization and spin current.

cond-mat.mes-hall↗
arXiv2002

Of Decoherent Electrons and Disordered Conductors

This lecture note reviews a variety of transport and thermodynamic measurements of electron decoherence time in low-dimensional conductors at low temperature. The mechanism of dephasing by electron interaction mediated by an arbitrarily small number of magnetic impurities is neither applicable to our linear-response measurements of weak localization, nor is it observed in the recent high-field measurements of the decoherence time in nominally pure quasi-one dimensional gold wires. The source of decoherence, after extensive experiments, still appears to be intrinsic.

cond-mat.mes-hall↗
arXiv2002

Anomalous Conductance Distribution in Quasi-One Dimension: Possible Violation of One-Parameter Scaling Hypothesis

We report measurements of conductance distribution in a set of quasi-one-dimensional gold wires. The distribution includes the second cumulant or the variance which describes the universal conductance fluctuations, and the third cumulant which denotes the leading deviation. We have observed an asymmetric contribution--or, a nonvanishing third cumulant--contrary to the expectation for quasi-one-dimensional systems in the noninteracting theories in the one-parameter scaling framework, which include the perturbative diagrammatic calculations and the random matrix theory.

cond-mat.mes-hall↗
arXiv2002

Extensions of Weak-Type Multipliers

In this paper we prove that if $Λ\in M_p(\mathbb R^N)$ and has compact support then $Λ$ is a weak summability kernel for $1<p<\infty$, where $M_p(\mathbb R^N)$ is the space of multipliers of $L^p(\mathbb R^N)$.

math.FA↗
arXiv2002

Summability Kernels for $L^p$ Multipliers

In this paper we have characterized the space of summability kernels for the case p=1 and p=2. For other values of p we give a necessary condition for a function $Λ$ to be a summability kernel. For the case p=1, we have studied the properties of measures which are transferred from $M(\mathbb Z)$ to $M(\mathbb R)$ through summability kernels. Further, we have extended every $l_p(\mathbb Z)$ sequences to $L^q(\mathbb R)$ multipliers for certain values of p and q.

math.FA↗
arXiv1997

Decoherence and Quantum Fluctuations

We show that the zero-point fluctuations of the intrinsic electromagnetic environment limit the phase coherence time in all mesoscopic systems at low temperatures. We derive this quantum noise limited dephasing time and its temperature dependence in the crossover to the thermal regime. Our results agree well with most experiments in 1D systems.

cond-mat.mes-hall↗