Condensed Matter Physics, Materials Science, Ceramics and Composites, Atomic and Molecular Physics, and Optics
19
Scopus Publications
Scopus Publications
Experimental and Theoretical Evidence of Weak Spin–Lattice Coupling in the Double Perovskite Sr2YRuO6 Hsiang‐Lin Liu, Bommareddy Poojitha, Yi‐Lin Lin, Hsiao‐Wen Chen, Chao‐Hung Du, Ting‐Hua Lu, Supratik Mukherjee, A. C. Garcia‐Castro, Ganapathy Vaitheeswaran Journal of Raman Spectroscopy, 2025 Sr2YRuO6 is a material that provides an ideal platform for studying magnetic frustration in three‐dimensional geometries. Herein, we combine Raman spectroscopy and density functional theory calculations to establish connections between the lattice dynamics and magnetic states in Sr2YRuO6 single crystals. The x‐ray diffraction profiles reveal that Sr2YRuO6 possesses an ordered double‐perovskite structure with distorted monoclinic symmetry. Three magnetic phase transitions are observed and linked to the presence of weak ferromagnetism at 135 K and short‐ and long‐range antiferromagnetic orderings at 32 and 26 K. The oxygen‐octahedron antistretching and stretching modes, observed at 570 and 766 cm−1, exhibit anomalies near the magnetic phase transition temperatures, indicating an intriguing interplay between the lattice and spin degrees of freedom. Their spin–phonon coupling constants of 0.7 cm−1 reflect the weak spin–lattice interactions in Sr2YRuO6.
Tuning the robust magnetic properties in M P S3 (M = Mn, Fe, and Ni) by proximity-induced Dzyaloshinskii-Moriya interactions Suvodeep Paul, Devesh Negi, Saswata Talukdar, Saheb Karak, Shalini Badola, Bommareddy Poojitha, Manasi Mandal, Sourav Marik, R. P. Singh, Nashra Pistawala, Luminita Harnagea, Aksa Thomas, Ajay Soni, Subhro Bhattacharjee, Surajit Saha Physical Review B, 2024 We have demonstrated the possibility to control the otherwise robust magnetic properties of transition-metal phosphorus trisulfides ($\text{Mn/Fe}\text{/}\mathrm{NiP}{\mathrm{S}}_{3}$) in their heterostructures with Weyl semimetallic $\mathrm{Mo}{\mathrm{Te}}_{2}$ which can be attributed to the Dzyaloshinskii-Moriya (DM) interactions at the interface of the two materials. While the DM interaction is known to scale with the strength of the spin-orbit coupling (SOC), we demonstrate using experiments on heterostructures with a variety of substrates (underlayers) hosting variable SOC and electronic density of states (DOS) that the effect of DM interaction strongly varies with the electronic DOS of the SOC-hosting layer as well as the spin orientation and degree of anisotropy associated with the magnetic layer.
Spin-phonon-charge coupling in the two-dimensional honeycomb lattice compound Ni2Te3 O8 Ajay Tiwari, D. Chandrasekhar Kakarla, Bommareddy Poojitha, Priyambada Sahoo, H. L. Liu, A. Dixit, C. W. Wang, T. W. Yen, M.-J. Hsieh, J.-Y. Lin, Jyothinagaram Krishnamurthy, Y. C. Lai, H. Chou, T. W. Kuo, Arkadeb Pal, H. D. Yang Physical Review B, 2023 A two-dimensional honeycomb-structured magnet ${\mathrm{Ni}}_{2}{\mathrm{Te}}_{3}{\mathrm{O}}_{8}$ was synthesized, characterized, and comprehensively investigated for its intriguing physical properties. DC magnetization, specific heat, and neutron diffraction revealed a long-range commensurate antiferromagnetic ordering at ${T}_{\mathrm{N}}\ensuremath{\sim}35\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ with a propagation vector $\mathbf{k}=(100)$. The magnetic sublattice comprises stacking distorted honeycomb layers along the $a$ axis. The ${\mathrm{Ni}}^{2+}$ spins on the honeycomb lattice are essentially pointing out of the layers and are antiferromagnetically coupled to the neighboring spins. Temperature ($T$) and magnetic field ($H$) dependent dielectric measurements indicated an apparent anomaly near ${T}_{\mathrm{N}}$, accompanied by a weak magnetodielectric effect. Raman mode renormalization and lattice anomalies near ${T}_{\mathrm{N}}$ demonstrated spin-lattice coupling through magnetoelastic and spin-phonon interactions. These findings highlight the fascinating interplay between spin, charge, and phonon degrees of freedom in ${\mathrm{Ni}}_{2}{\mathrm{Te}}_{3}{\mathrm{O}}_{8}$.
Spin-phonon coupling in ferrimagnet spinel CoMn2O4 Bommareddy Poojitha, Aswin Shaji, Shalini Badola, Surajit Saha Journal of Chemical Physics, 2022 Coupling of material properties provides new fundamental insights and possibilities toward multifunctional devices. The spinel structures display strong coupling between different order parameters, as a consequence, exhibiting many fascinating properties, such as multiferroicity and superconductivity. Here, we have investigated the structural, magnetic, and vibrational properties of mixed-spinel CoMn2O4 stabilized in distorted tetragonal structures as evidenced from x-ray diffraction measurements. Magnetization measurements reveal two ferrimagnetic phase transitions at 185 and 90 K. Raman scattering measurements reveal the renormalization of phonon parameters for a few phonon modes at low temperatures, arising from spin–phonon coupling. The obtained value for λS2 is ∼2 cm−1. The strength of spin–phonon coupling (λ) is estimated according to the spins involved in the corresponding lattice vibrations and discussed.
Electron–phonon coupling in APd3O4: A = Ca, Sr, and Sr0.85Li0.15 Bommareddy Poojitha, B H Reddy, Aprajita Joshi, Ankit Kumar, Asif Ali, R S Singh, Surajit Saha Journal of Physics Condensed Matter, 2021 Here we have investigated the role of electron phonon coupling on the Raman spectrum of narrow bandgap semiconductors APd3O4 (A = Ca, Sr) and hole-doped system Sr0.85Li0.15Pd3O4. Four Raman active phonons are observed at room temperature for all three compounds as predicted by factor group analysis. The lowest energy phonon (∼190/202 cm−1) associated with Pd vibrations is observed to exhibit an asymmetric Fano-like lineshape in all the three compounds, indicating the presence of an interaction between the phonon and the electronic continuum. The origin of the electronic continuum states and electron–phonon coupling are discussed based on our laser power- and temperature-dependent Raman results. We have observed an enhanced strength of electron–phonon coupling in Sr0.85Li0.15Pd3O4 at low temperatures which can be attributed to the metallicity in this doped compound.
Hexagonal Boron Nitride-Graphene Heterostructures with Enhanced Interfacial Thermal Conductance for Thermal Management Applications Saheb Karak, Suvodeep Paul, Devesh Negi, Bommareddy Poojitha, Saurabh Kumar Srivastav, Anindya Das, Surajit Saha ACS Applied Nano Materials, 2021 Atomically thin monolayers of graphene show excellent electronic properties which have led to a great deal of research on their use in nanoscale devices. However, heat management of such nanoscale devices is essential in order to improve their performance. Graphene supported on hexagonal boron nitride (h-BN) substrate has been reported to show enhanced (opto)electronic and thermal properties as compared to extensively used SiO2/Si supported graphene. Motivated by this, we have performed temperatureand power-dependent Raman Spectroscopic measurements on four different types of (hetero)structures: (a) h-BN (BN), (b) graphene (Gr), (c) h-BN on graphene (BG), and (d) graphene encapsulated by h-BN layers from both top and bottom (BGB), all supported on SiO2/Si substrate. We have estimated the values of thermal conductivity (κ) and interfacial thermal conductance per unit area (g) of these four (hetero)structures to demonstrate the structure-activity (thermal) relationship. We report here the values of κ and g for h-BN supported on SiO2/Si as 280.0±58.0 Wm -1 K -1 and 25.6±0.4 MWm -2 K -1 , respectively. More importantly, we have observed an improvement in both thermal conductivity and interfacial thermal conductance per unit area in the heterostructures which ensures a better heat dissipation in devices. The κ and g of h-BN encapsulated graphene on SiO2/Si (BGB) sample was observed to be 850.0±81.0 Wm -1 K -1 and 105±1 MWm -2 K -1 , respectively, as opposed to 600.0±93.0 Wm -1 K -1 and 1.15±0.40 MWm -2 K -1 , respectively, for graphene on SiO2/Si substrate. Therefore, we propose that for graphene-based nanoscale devices, encapsulation with h-BN is a better alternative to address heat management issues.
