arXiv subjects

Satadeep Bhattacharjee

Publications and source records attributed to Satadeep Bhattacharjee.

76 records · Page 5Linked to original sources

arXiv2010

Dielectric properties and spin-phonon coupling in multiferroic double perovskite Bi$_2$CoMnO$_6$

First-principles electronic structure calculations have been performed for the double perovskite Bi$_2$CoMnO$_6$ in its non-centrosymmetric polar state using generalized gradient approximation plus Hubbard U approach. We find that while Co is in a high spin state, Mn is in an intermediate spin state. The calculated dynamical charge tensors are anisotropic reflecting a low-symmetry structure of the compound. Magnetic structure dependent phonon frequencies indicate the presence of spin-phonon coupling. Using Berry phase method, we obtain a spontaneous electronic polarization of 5.88 $μC/cm^2$ which is close to the experimental value observed for a similar compound, Bi$_2$NiMnO$_6$.

cond-mat.mtrl-sci↗

arXiv2008

Engineering multiferroism in CaMnO$_3$

From first-principles calculations, we investigate the structural instabilities of CaMnO$_3$. We point out that, on top of a strong antiferrodistortive instability responsible for its orthorhombic ground-state, the cubic perovskite structure of CaMnO$_3$ also exhibit a weak ferroelectric instability. Although ferroelectricity is suppressed by antiferrodistortive oxygen motions, we show that it can be favored using strain or chemical engineering in order to make CaMnO$_3$ multiferroic. We finally highlight that the FE instability of CaMnO$_3$ is Mn-dominated. This illustrates that, contrary to the common believe, ferroelectricity and magnetism are not necessarily exclusive but can be driven by the same cation.

cond-mat.mtrl-sci↗

arXiv2008

First-principle calculation of the dielectric and dynamical properties of orthorhombic CaMnO$_{3}$

The structural, dielectric and dynamical properties of the low temperature antiferromagnetic orthorhombic phase of CaMnO$_3$ have been computed from first principles using a density functional theory approach within the local spin density approximation. The theoretical structural parameters are in good agreement with experiment. The full set of infrared and Raman zone-center phonons is reported and compared to experimental data. It is shown that coherently with the anomalous Born effective charges and the presence of low frequency polar modes, the static dielectric constant is very large and highly anisotropic.

cond-mat.mtrl-sci↗

arXiv2000

Scaling of transition temerature and CuO_2 plane buckling in the cuprate superconductors

Recently it is seen\cite{Nature},that both $\rm{T}_c$ and the buckling of the $CuO_2$ planes goes through a maximum at the same doping level. We show that only for optimal doping concentration the Fermi surface touches the M($0,π$) point in the BZ, where the matrix element for interlayer pair tunneling amplitude is largest, so that the gain in delocalization energy by tunneling(in pairs) along the $c$ axis is largest. Buckling of the planes on the other hand modulates the separation between the planes and thereby modulates the interlayer pair tunneling amplitude. That is why both $\rm{T}_c$ and buckling angle(Oxygen atom displacement out of the plane) scales the same way with doping concentration. We have calculated $\rm{T}_c$ and buckling angle for various doping concentration. The agreement with experiment is remarkably good. We also point out the possible reason for large(about 1 percent) change of the buckling mode phonon frequency, accross the transition temperature. scattering

cond-mat↗