arXiv subjects

Sathiyamoorthy Buvaneswaran

Publications and source records attributed to Sathiyamoorthy Buvaneswaran.

5 recordsLinked to original sources

arXiv2026

Polar Charge-Ordered States in BiFeO$_3$/CaFeO$_3$ Superlattice

Oxide superlattices represent a potent avenue for tailoring emergent electronic phases through sophisticated interfacial charge transfer and dynamic lattice distortions. This study systematically investigates the structural and electronic attributes of the BiFeO$_3$/CaFeO$_3$ superlattice, leveraging a comprehensive approach that integrates first-principles computations with detailed symmetry-mode analysis. The strategic integration of polar bismuth ferrite alongside charge-transfer calcium ferrite instigates profound lattice instabilities, notably manifest in octahedral rotations and cooperative FeO$_6$ breathing modes that might not necessarily be soft. However, their synergistic coupling stabilizes a non-centrosymmetric $Pc$ ground state that intrinsically features polar charge ordering of Fe ions. This resultant phase ingeniously unifies C-type antiferromagnetism with robust ferroelectric semiconductor characteristics, exhibiting a calculated indirect band gap of about 0.6 eV. Our discoveries firmly establish ferrite superlattices as an exceptionally versatile and tunable platform for the rational design of next-generation multifunctional materials, offering precise control over polarization, charge ordering phenomena, and electronic transport behavior via advanced interface and strain engineering techniques.

cond-mat.mtrl-sci↗

arXiv2025

Ferroelectric metal-organic frameworks as wide band gap materials

Wide band gap materials are particularly relevant at high temperatures. The band gap shrinkage at higher temperatures prevents device applications with narrow band gap semiconductors. Considering $α$-phase strontium cyanurate as a prototype structure, we identify a group of metal-organic frameworks (MOFs) that exhibit ultra-wide band gaps ranging from 5.5 to 5.7 eV. Recently, a strontium cyanurate compound was found to undergo a phase transition from a high-symmetry $β$-phase to a low-symmetry ferroelectric $α$-phase when the temperature was reduced. In the present study, utilizing group theory techniques, we unravel that a zone-center $Γ_2^-$ phonon mode modifies our structures from high-symmetry $β$-phase to a low-symmetry $α$-phase for A$_3$(O$_3$C$_3$N$_3$)$_2$ MOFs with A = Mg, Ca, Sr, and Ba. We implement first-principles calculations to investigate structural, ferroelectric, and optical properties of these compounds in $α$-phase. The switching barriers between bistable polar states are also estimated. Further, to realize their feasibility, we examine the dynamical and thermal stabilities for all of these MOFs.

cond-mat.mtrl-sci↗

arXiv2025

Intervention Strategies for Polarization Switching in Hybrid Improper Ferroelectrics

The potential of hybrid improper ferroelectrics (HIFs) in electronic and spintronic devices hinges on their ability to switch polarization. Although the coupling between octahedral rotation and tilt is well established, the factors that govern switching barriers remain elusive. In this study, we explore this area to demonstrate the critical role of causal reasoning in uncovering the mechanisms to control the ferroelectric switching barrier in HIFs. By combining causal discovery, causal interventions, and first-principles simulations, we identify tolerance factor, A-site cation radii mismatch, epitaxial strain, and octahedral rotation/tilt as key parameters and quantify how their interplay directly influences switching barrier. Three key insights emerge from our work: (a) the analysis identifies the structural descriptors controlling polarization reversal across a broad family of A-site-layered double perovskites and superlattices, (b) it uncovers non-trivial, material-specific rotation-tilt mechanisms, including a counterintuitive cooperative pathway where both rotation and tilt change while lowering the barrier, an effect mostly inaccessible to conventional Landau or first-principles-based approaches and (c) it maps these material-specific mechanisms to experimentally realizable parameters, showing that epitaxial strain from orthorhombic substrates (e.g., NdScO$_3$, NdGaO$_3$) selectively tunes octahedral distortions to achieve barrier reduction across varied compositions. These results establish actionable, materials-by-design principles linking composition, structure, and strain to polarization switching, while highlighting the potential of causal reasoning to guide intelligent, mechanism-driven strategies for engineering complex functional oxides.

cond-mat.mtrl-sci↗

arXiv2025

Polarization-Magnetization Coupling in Visible Light Ferroelectric Double Perovskites

The bulk photovoltaic effect (BPVE), arising from broken inversion symmetry in ferroelectrics, offers a distinct pathway toward high-efficiency next-generation photovoltaics. We propose and investigate A/A$^\prime$-ordered double perovskites KLaFeMoO$_6$ and NaLaFeMoO$_6$ as promising single-phase ferroelectric photovoltaic (FE-PV) materials. First-principles calculations reveal robust P2$_1$ symmetry with A-site layer and B-site rock-salt ordering, accompanied by hybrid improper ferroelectricity driven by $a^{-}a^{-}c^{+}$ octahedral tilts. Both compounds exhibit significant spontaneous polarization and indirect band gaps of $\sim$ 1.8 eV, well suited for visible-light absorption ($>$10$^5$ cm$^{-1}$). Low carrier effective masses along the polar axis indicate efficient charge transport. \textit{Ab initio} molecular dynamics simulations (AIMD) show that polarization-coupled magnetization switching is feasible above room temperature, making these materials suitable for room-temperature applications.

cond-mat.mtrl-sci↗

arXiv2025

Unveiling Insulating Ferro and Ferrimagnetism in Double-Double Perovskite Oxides

The emergence of ferro- and ferrimagnetic behavior in insulating materials is uncommon, largely due to Hund's rules. Utilizing symmetry analysis, first-principles methods, and classical Monte Carlo simulations, \textcolor{black}{we report technologically important insulating ferro and ferrimagnetic double-double perovskite oxides. Our study predicts LaA$^{\prime}$MnNiO$_6$ (A$^{\prime}$ = V, Cr, Mn, Co, and Ni) as promising candidates for spintronic and optical applications exhibiting band gaps between 1.3 eV and 1.9 eV. We explain the mechanisms driving band gap openings and magnetic exchange interactions in these ferro and ferrimagnetic compounds. Monte Carlo simulations, together with state-of-the-art orbital-decomposed exchange parameter analysis, reveal intriguing variations in magnetic transition temperatures (up to 242 K) and the corresponding exchange mechanisms in all LaA$^{\prime}$MnNiO$_6$ compounds.} In addition, we assess the thermodynamic and dynamic stability of these compounds to comment on the feasibility of these systems.

cond-mat.mtrl-sci↗