13 research outputs found
Role of Te in the low dimensional multiferroic material FeTe2O5Br
Using first principles density functional calculations, we study the
electronic structure of the low-dimensional multiferroic compound FeTe2O5Br to
investigate the origin of the magnetoelectric (ME) effect and the role of Te
ions in this system. We find that without magnetism even in the presence of
Te-5s lone pairs, the system remains centrosymmetric due to the antipolar
orientation of the lone pairs. Our study shows that the exchange striction
within the Fe tetramers as well as between them is responsible for the ME
effect in FeTe2O5Br. We also find that the Te^4+ ions play an important role in
the inter-tetramer exchange striction as well as contribute to the electric
polarization in FeTe2O5Br, once the polarization is triggered by the magnetic
ordering.Comment: 8 pages, 8 figures, Journal version:
http://link.aps.org/doi/10.1103/PhysRevB.88.09440
ELECTRONIC STRUCTURE OF NOVEL MAGNETIC SYSTEMS
The present thesis is devoted to the study of low dimensional quantum spin systems and
low dimensional systems that exhibit multiferroic behavior.
Using ab initio density functional theory we have studied the electronic and magnetic properties
of a spin gap compound Sr2Cu(BO3)2. We have calculated the hopping and exchange
interactions between various Cu ions and derived the low energy spin model for the system.
The spin model turns out to be a system of decoupled spin ladders with strong rung coupling.
The validity of the model is checked by calculating the magnetic susceptibility as a function
of temperature and magnetization as a function of temperature as well as magnetic field using
Quantum Monte Carlo technique and comparison of the calculated results with the available
experimental data. Our results suggest that the above model is appropriate to describe the low
energy physics of Sr2Cu(BO3)2.
We have studied the electronic structure and magnetic properties of frustrated quantum
spin systems which include diamond chain antiferromagnets Ba3Cu3X4O12 (X = Sc, In) and
also the proposed staircase Kagome lattice system PbCu3TeO7. With the aid of first principles
calculations we have identified the dominant exchange paths of these systems which are not
obvious from structural considerations. Our estimation for the Curie-Wiess temperature from the computed exchange interactions compares well with experiments. The calculated exchange couplings lead to long range magnetic order, in contrast to the expectation from the structural considerations. Using first principles density functional calculations, we have studied the electronic structure of the low dimensional multiferroic compound FeTe2O5Br to investigate the origin of
magnetoelectric (ME) effect and the role of Te ions in this system. We find that without magnetism even in the presence of Te 5s lone pairs, the system remains centrosymmetric due to the antipolar orientation of the lone pairs. Our study shows that the exchange striction within the Fe tetramers as well as between them is responsible for the magnetoelectric (ME) effect in FeTe2O5Br. We also find that the Te4+ ions play an important role in the inter tetramer exchange striction as well as contribute to the electric polarization in FeTe2O5Br, once the polarization is triggered by the magnetic ordering. Finally we have studied the magnetic and ferroelectric properties of two dimensional triangular
lattice antiferromagnetic AgFeO2 and compared with the isostructural system CuFeO2. Our calculations reveal spin orbit coupling has a profound effect on the magnetic and ferroelectric
properties of AgFeO2. Calculations of ferroelectric polarization suggest that the spontaneous polarization arises from noncollinear spin arrangement via spin orbit coupling. Our calculations also indicate that in addition to electronic contribution, the lattice mediated contribution to the polarization are also important for AgFeO2.The research was conducted under the supervision of Prof. Indra Dasgupta of the Solid State Physics division under SPS [ School of Physical Sciences]The research was carried out under sponsorship Council of Scientific and Industrial Research (CSIR) (Grant No.09/080(0615)/2008-EMR -1) for research fellowship, financial support from MONAMI and infrastructural support from IACS
Simulation-Based Optimisation of Demand and Supply for Ridesourcing Services in an urban environment: A Case Study of Perth Metropolitan Area
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Probing the
An interaction at the tree level is a common feature of new physics models that feature scalar triplets. In this study, we aim to probe the strength of the aforementioned interaction in a model-agnostic fashion at the futuristic 27 TeV proton-proton collider. We assume that the couples dominantly to () and (t, b) and specifically study the processes that involve the vertex at the production level, that is, and . Moreover, we look into both decays for either production process. Our investigations reveal that the production process has a greater reach compared to . Moreover, the discovery potential of a charged Higgs improves markedly with respect to the earlier studies corresponding to lower centre-of-mass energies. Finally, we recast our results in the context of the popular Georgi–Machacek model
The Effect of Different Metal Electrodes on the Performance of ZnO/p-Si/Al Hetero-Structure for Hydrogen Detection
Channel-Assisted Proton Conduction Behavior in Hydroxyl-Rich Lanthanide-Based Magnetic Metal–Organic Frameworks
Two new lanthanide-based
3D metal–organic frameworks (MOFs), {[Ln(L)(Ox)(H<sub>2</sub>O)]<sub><i>n</i></sub>·<i>x</i>H<sub>2</sub>O} [Ln = Gd<sup>3+</sup> and <i>x</i> = 3 (<b>1</b>) and Dy<sup>3+</sup> and <i>x</i> = 1.5 (<b>2</b>); H<sub>2</sub>L = mucic acid; OxH<sub>2</sub> = oxalic acid] showing
interesting magnetic properties and channel-mediated proton conduction
behavior, are presented here. Single-crystal X-ray structure analysis
shows that, in complex <b>1</b>, the overall structure originates
from the mucate-bridged gadolinium-based rectangular metallocycles.
The packing view reveals the presence the two types of hydrophilic
1D channels filled with lattice water molecules, which are strongly
hydrogen-bonded with coordinated water along the <i>a</i> and <i>b</i> axes, whereas for complex <b>2</b>,
the 3D framework originates from a carboxylate-bridged dysprosium-based
criss-cross-type secondary building block. Magnetic studies reveal
that <b>1</b> exhibits a significant magnetic entropy change
(−Δ<i>S</i><sub>M</sub>) of 30.6 J kg<sup>–1</sup> K<sup>–1</sup> for Δ<i>H</i>= 7 T at 3 K.
Our electronic structure calculations under the framework of density
functional theory reveal that exchange interactions between Gd<sup>3+</sup> ions are weak and of the antiferromagnetic type. Complex <b>2</b> shows field-induced single-molecule-magnetic behavior. Impedance
analysis shows that the proton conductivity of both complexes reaches
up to the maximum value of 4.7 × 10<sup>–4</sup> S cm<sup>–1</sup> for <b>1</b> and 9.06 × 10<sup>–5</sup> S cm<sup>–1</sup> for <b>2</b> at high temperature
(>75 °C) and relative humidity (RH; 95%). The Monte Carlo
simulations confirm the exact location of the adsorbed water molecules
in the framework after humidification (RH = 95%) for <b>1</b>. Further, the results from computational simulation also reveal
that the presence of a more dense arrangement of adsorbed water molecules
through hydrogen bonding in a particular type of channel (along the <i>a</i> axis) contributes more to the proton migration compared
to the other channel (along the <i>b</i> axis) in the framework