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M. M. Islam

Publications and source records attributed to M. M. Islam.

18 recordsLinked to original sources
arXiv2025

Investigation of magnetic ordering with spin reorientation transition and optical properties in Dy$_2$CoCrO$_6$ nanomaterials

This study reports the synthesis and physical properties of polycrystalline Dy$_2$CoCrO$_6$ (DCCO) nanoparticles. Analysis of the powder X-ray diffraction (XRD) pattern using Rietveld refinement showed that the compound crystallizes in an orthorhombic crystal structure with a space group Pbnm. The particle size of approximately 57 nm was confirmed through micrographs obtained from field emission scanning electron microscopy and transmission electron microscopy. The X-ray photoelectron spectroscopy (XPS) investigations identified a mixed-valence state of Co and Cr cations. Magnetic susceptibility data indicated Curie-Weiss behavior in the temperature range 140-340 K and the onset of antiferromagnetic interactions with a Neel temperature of 119 K. At 31 K, DCCO shows spin reorientation transition from $\Gamma_4$(G$_x$A$_y$F$_z$) to $\Gamma_2$(F$_x$C$_y$G$_z$). Furthermore, room-temperature magnetization measurements demonstrated the antiferromagnetic behavior with weak ferromagnetic interactions at low temperatures. Additionally, DCCO exhibited semiconducting behavior with a direct optical bandgap of 1.97 eV, indicating promise for visible-light-driven energy harvesting and catalytic applications.

cond-mat.mtrl-sci↗
arXiv2020

Structural and Magnetic Characterization of CuxMn1-xFe2O4 (x= 0.0, 0.25) Ferrites Using Neutron Diffraction and Other Techniques

Manganese ferrite (MnFe2O4) and copper doped manganese ferrite (Mn0.75Cu0.25Fe2O4) soft materials were synthesized through solid-state sintering method. The phase purity and quality were confirmed from x-ray diffraction patterns. Then the samples were subjected to neutron diffraction experiment and the diffraction data were analyzed using FullProf software package. The surface morphology of the soft material samples was studied using a scanning electron microscope (SEM). Crystal parameters, crystallite parameters, occupancy at A and B sites of the spinel structure, magnetic moments of the atoms at various locations, symmetries, oxygen position parameters, bond lengths etc. were measured and compared with the reference data. In MnFe2O4, both octahedral (A) and tetrahedral (B) positions are shared by Mn2+ and Fe2+/3+ cations, here A site is predominantly occupied by Fe2+ and B site is occupied by Mn at 0.825 occupancy. The Cu2+ ions in Cu0.25Mn0.75Fe2O4 mostly occupy the B site. Copper mostly occupy the Octahedral (16d) sites. The length of the cubic lattice decreases with the increasing Copper content. The magnetic properties, i.e. A or B site magnetic moments, net magnetic moment etc. were measured using neutron diffraction analysis and compared with the bulk magnetic properties measured with VSM studies.

cond-mat.mtrl-sci↗
arXiv2017

pp Elastic Scattering at LHC Proton Structure Outer Cloud - Inner Shell - Gluon Core

Our investigation of high energy $\rm{pp}$ and $\bar{\rm{p}}\rm{p}$ elastic scattering over the last two decades has led us to consider that the proton has three regions: i) an outer region consisting of a quark-antiquark ($\rm{q}\bar{\rm{q}}$) condensate ground state (also described as quark-antiquark outer cloud), ii) an inner shell of baryonic charge of size ~0.44 fm, and iii) a core of size ~0.2 fm, where the three valence quarks of a proton with baryonic charges are confined. The proton structure that has emerged leads to four main elastic scattering processes in $\rm{pp}$ scattering. The first process, which gives rise to diffraction scattering, is due to a glancing collision of the outer cloud of one proton with that of another proton. In a $\bar{\rm{p}}\rm{p}$ glancing collision the corresponding process occurs. The second process involves multiple ω-exchanges. The third process in $\rm{pp}$ scattering is quark-quark scattering via gluon-gluon interaction. The fourth process - which appears for the first time in our investigation of $\rm{pp}$ scattering - is a glancing collision at the boundary of a proton cloud with that of the other proton cloud. To describe quantitatively the four processes, their parameters have been determined. For this purpose, we investigated $\rm{pp}$ 7 TeV dσ/dt measured by the TOTEM Collaboration and $\bar{\rm{p}}\rm{p}$ 1.96 TeV dσ/dt measured by the D0 Collaboration. Our calculated $\rm{pp}$ elastic dσ/dt at 13 TeV has no oscillations in the large |t| region, in good agreement with the preliminary TOTEM measurements.

hep-ph↗
arXiv2013

High Energy pp Elastic Scattering in Condensate Enclosed Chiral Bag Model and TOTEM Elastic Measurements at LHC at 7 TeV

We study high energy $\small{\rm{pp}}$ and $\small{\rm{\bar {p}p}}$ elastic scattering in the TeV region based on an effective field theory model of the proton. We phenomenologically investigate the main processes underlying elastic scattering and quantitatively describe the measured elastic d$\smallσ$/dt at energies 7.0 TeV (LHC $\small{\rm{pp}}$), 1.96 TeV (Tevatron $\small{\rm{\bar {p}p}}$), and 0.630 TeV (SPS $\small{\rm{\bar {p}p}}$). Finally, we give our prediction for $\small{\rm{pp}}$ elastic d$\smallσ$/dt at 14 TeV that will be measured by the TOTEM Collaboration.

hep-ph↗
arXiv2013

Energy ordering of grain boundaries in Cr2O3: Insights from theory

The grain boundaries, GBs, of corundum Cr2O3 are known to play an important role in the diffusion of ions within the oxide, which is an important phenomenon for the corrosion of the stainless steels. The extent of the growth of oxide layers in stainless steel depends upon which interfaces are preferred within Cr2O3. Therefore, we have constructed four different grain boundary planes (rhombohedral, basal, prismatic and pyramidal) and their various associated interface symmetries known in literature for corundum Al2O3. Their structural, electronic, and energetic properties are investigated theoretically with periodic calculations using the DFT+U approach. We find that the prismatic screw GB with a Cr-O plane interface is the energetically preferred GB with the rhombohedral GB with screw symmetry and Cr vacancy termination being the second energetically preferred GB. The increase of the number of in-plane Cr atoms at the interface of prismatic GB enhances the stability which is also evident in the electronic density of states.

cond-mat.mtrl-sci↗
arXiv2010

Doping Dependence of Thermal Oxidation on n-type 4H-SiC

The doping dependence of dry thermal oxidation rates in n-type 4H-SiC was investigated. The oxidation was performed in the temperature range 1000C to 1200C for samples with nitrogen doping in the range of 6.5e15/cm3 to 9.3e18/cm3, showing a clear doping dependence. Samples with higher doping concentrations displayed higher oxidation rates. The results were interpreted using a modified Deal-Grove model. Linear and parabolic rate constants and activation energies were extracted. Increasing nitrogen led to an increase in linear rate constant pre-exponential factor from 10-6m/s to 10-2m/s and the parabolic rate constant pre-exponential factor from 10e9m2/s to 10e6m2/s. The increase in linear rate constant was attributed to defects from doping-induced lattice mismatch, which tend to be more reactive than bulk crystal regions. The increase in the diffusion-limited parabolic rate constant was attributed to degradation in oxide quality originating from the doping-induced lattice mismatch. This degradation was confirmed by the observation of a decrease in optical density of the grown oxide films from 1.4 to 1.24. The linear activation energy varied from 1.6eV to 2.8eV, while the parabolic activation energy varied from 2.7eV to 3.3eV, increasing with doping concentration. These increased activation energies were attributed to higher nitrogen content, leading to an increase in effective bond energy stemming from the difference in C-Si (2.82eV) and Si-N (4.26eV) binding energies. This work provides crucial information in the engineering of SiO2 dielectrics for SiC MOS structures, which typically involve regions of very different doping concentrations, and suggests that thermal oxidation at high doping concentrations in SiC may be defect mediated.

cond-mat.mtrl-sci↗
arXiv2009

Deep-Elastic pp Scattering at LHC from Low-x Gluons

Deep-elastic pp scattering at c.m. energy 14 TeV at LHC in the momentum transfer range 4 GeV*2 < |t| < 10 GeV*2 is planned to be measured by the TOTEM group. We study this process in a model where the deep-elastic scattering is due to a single hard collision of a valence quark from one proton with a valence quark from the other proton. The hard collision originates from the low-x gluon cloud around one valence quark interacting with that of the other. The low-x gluon cloud can be identified as color glass condensate and has size ~0.3 F. Our prediction is that pp differential cross section in the large |t| region decreases smoothly as momentum transfer increases. This is in contrast to the prediction of pp differential cross section with visible oscillations and smaller cross sections by a large number of other models.

hep-ph↗
arXiv2007

pp Elastic Scattering at LHC in a Nucleon-Structure Model

We predict pp elastic differential cross sections at LHC at c.m. energy 14 TeV and momentum transfer range |t| = 0 - 10 GeV*2 in a nucleon-structure model. In this model, the nucleon has an outer cloud of quark-antiquark condensed ground state, an inner shell of topological baryonic charge (r ~ 0.44F) probed by the vector meson omega, and a central quark-bag (r ~ 0.2F) containing valence quarks. We also predict elastic differential cross section in the Coulomb-hadronic interference region. Large |t| elastic scattering in this model arises from valence quark-quark scattering, which is taken to be due to the hard-pomeron (BFKL pomeron with next to leading order corrections). We present results of taking into account multiple hard-pomeron exchanges, i.e. unitarity corrections. Finally, we compare our prediction of pp elastic differential cross section at LHC with the predictions of various other models. Precise measurement of pp elastic differential cross section at LHC by the TOTEM group in the |t| region 0 - 5 GeV*2 will be able to distinguish between these models.

hep-ph↗
arXiv2005

pp Elastic Scattering in Near Forward Direction at LHC and Nucleon Structure

We predict pp elastic differential cross section at LHC at the c.m. energy 14 TeV and momentum transfer range |t| = 0-10 GeV*2, which is planned to be measured by the TOTEM group. The field theory model underlying our phenomenological investigation describes the nucleon as a composite object with an outer cloud of quark-antiquark condensate, an inner core of topological baryonic charge, and a still smaller quark-bag of valence quarks. The model satisfactorily describes the asymptotic behavior of sigma-total(s) and rho(s) as well as the measured antiproton-proton elastic differential cross section at c.m. energies 546 GeV, 630 GeV, and 1.8 TeV. The large |t| elastic amplitude of the model incorporates the QCD hard pomeron (BFKL Pomeron plus next to leading order approximations), the perturbative dimensional counting behavior, and the confinement of valence quarks in a small region within the nucleon. Our predicted pp elastic differential cross section at LHC is compared with those of Bourrely et al. and Desgrolard et al.

hep-ph↗
arXiv2005

Near Forward pp Elastic Scattering at LHC and Nucleon Structure

High energy proton-proton and antiproton-proton elastic scattering are studied first in a model where the nucleon has an outer cloud and an inner core. Elastic scattering is viewed as due to two processes: a) diffraction scattering originating from cloud-cloud interaction; b) a hard or large |t| scattering originating from one nucleon core scattering off the other via vector meson omega exchange, while their outer clouds interact independently. The omega-exchange amplitude shows that omega behaves like an elementary vector meson at high energy, contrary to a regge pole behavior. This behavior, however, can be understood in the nonlinear sigma-model where omega couples to a topological baryonic current like a gauge boson, and the nucleon is described as a topological soliton. Further investigation shows that the underlying effective field theory model is a gauged linear sigma-model that has not only the pion sector and the Wess-Zumino-Witten action of the nonlinear sigma-model, but also a quark-scalar sector. The nucleon structure that emerges is that the nucleon has an outer cloud of quark-antiquark condensed ground state, an inner core of topological baryonic charge probed by omega, and a still smaller quark-bag containing massless valence quarks. Large |t| pp elastic scattering is attributed to valence quark-quark elastic scattering, which is taken to be due to the hard pomeron. The model is applied to predict pp elastic differential cross section at LHC at c.m. energy 14 TeV and |t| = 0 - 10 GeV*2. If our predicted differential cross section is quantitatively confirmed by precise measurement at LHC by the TOTEM group, then it will indicate that various novel ideas developed over the last four decades to describe the nucleon combine and lead to a unique physical description of its structure.

hep-ph↗
arXiv2004

pp Elastic Scattering at LHC in Near Forward Direction

We predict pp elastic differential cross section at LHC at the c.m. energy sqrt(s) = 14 TeV and momentum transfer range |t| = 0 - 10 GeV^2, which is planned to be measured by the TOTEM group. The field theory model underlying our phenomenological investigation describes the nucleon as a composite object with an outer cloud of quark-antiquark condensate, an inner core of topological baryonic charge, and a still smaller quark-bag of valence quarks. The model satisfactorily describes the asymptotic behavior of total cross section as a function of s and the real to imaginary ratio of the forward scattering amplitude as a function of s. It also describes well the the measured antiproton-proton elastic differential cross sections at sqrt(s)= 546 GeV, 630 GeV, and 1.8 TeV. The large |t| elastic amplitude of the model incorporates the BFKL Pomeron in next to leading order approximation, the perturbative dimensional counting behavior, and the confinement of valence quarks in a small region within the nucleon.

hep-ph↗
arXiv2003

pp Elastic Scattering at LHC and Nucleon Structure (Conference Report)

High energy elastic pp differential cross section at LHC at the c.m. energy 14 TeV is predicted using the asymptotic behavior of sigma-tot(s) and rho(s), and the measured pbar-p differential cross section at sqrt{s}=546 GeV. The phenomenological investigation has progressively led to an effective field theory model that describes the nucleon as a chiral bag embedded in a quark-antiquark condensed ground state. The measurement of pp elastic scattering at LHC up to large |t| >~ 10 GeV^2 by the TOTEM group will be crucial to test this structure of the nucleon.

hep-ph↗
arXiv2003

p p Elastic Scattering at LHC and Nucleon Structure

High energy elastic $p p$ scattering at the Large Hadron Collider (LHC) at c.m. energy 14 TeV is predicted using the asymptotic behavior of $σ_{tot}(s)$ and $ρ(s)$ known from dispersion relation calculations and the measured elastic $\bar p p$ differential cross section at $\sqrt{s} = 546 {\rm GeV}$. The effective field theory model underlying the phenomenological analysis describes the nucleon as having an outer cloud of quark-antiquark condensed ground state, an inner core of topological baryonic charge of radius $\simeq 0.44F$ and a still smaller valence quark-bag of radius $\lesssim 0.1 {\rm F}$. The LHC experiment TOTEM (Total and Elastic Measurement), if carried out with sufficient precision from $|t| = 0$ to $|t| > 10 {\rm GeV^2}$, will be able to test this structure of the nucleon.

hep-ph↗
arXiv2000

pp Elastic Scattering at LHC and Signature of Chiral Phase Transition at Large |t|

A model of $pp$ and $\bar{p}p$ elastic scattering developed previously to analyze ISR and SPS Collider data is extended to predict $pp$ elastic differential cross section at LHC at c.m. energy of 14 TeV and momentum transfer range $|t|=0$ - 10 GeV$^2$. Role of the gauged linear $σ$-model as an underlying field theory model describing nucleon structure and elastic scattering is discussed. Possibility of finding evidence of a chiral phase transition at large $|t|$ in the proposed TOTEM project at LHC is pointed out.

hep-ph↗
arXiv1998

Describing Hot and Dense Nuclear Matter with Gauged Linear sigma-Model

To describe nuclear matter at high temperature and high baryon density appropriate for RHIC and LHC, an effective theory is proposed. Three developments underlie the effective theory: (1) relativistic mean field theory description of nuclear matter with mesons mediating interactions; (2) topological soliton description of the nucleon with hidden local symmetry; (3) phenomenological knowledge of nucleon-nucleon interaction and nucleon structure obtained from elastic NN scattering at c.m. energies of hundreds of GeV. When these developments are combined together, a gauged linear sigma-model with anomalous action and condensed quark-antiquark ground state emerges as the effective theory.

nucl-th↗
arXiv1996

Anomalous Chiral Action from the Path-Integral

By generalizing the Fujikawa approach, we show in the path-integral formalism: (1) how the infinitesimal variation of the fermion measure can be integrated to obtain the full anomalous chiral action; (2) how the action derived in this way can be identified as the Chern-Simons term in five dimensions, if the anomaly is consistent; (3) how the regularization can be carried out, so as to lead to the consistent anomaly and not to the covariant anomaly. Our method uses Schwinger's ``proper-time'' representation of the Green's function and the gauge invariant point-splitting technique. We find that the consistency requirement and the point-splitting technique allow both an anomalous and a non-anomalous action. In the end, the nature of the vacuum determines whether we have an anomalous theory, or, a non-anomalous theory

hep-th↗
arXiv1995

Probing Nucleon Structure via High Energy Elastic Scattering

Analyses of high energy elastic pp and $\bar pp$ scattering data from CERN ISR and SPS Collider seem to provide strong evidence in favor of the gauged nonlinear sigma-model of the nucleon. This model describes the nucleon as a topological soliton and introduces the vector mesons omega, rho, a1 as gauge bosons. The model, however, needs to be extended to include an explicit quark sector, where left and right quarks interact via a scalar field. A critical behavior of the scalar field results in a phase transition to a condensed quark-antiquark ground state. The latter can provide the outer cloud of the nucleon, which is responsible for diffraction scattering. If the nucleon is probed deeper via high energy elastic scattering, then evidence for the phase transition may emerge from a rapid change in the behavior of the differential cross-section.

hep-ph↗