Browsing by Author "Satya Vijay Kumar"

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Anharmonic phonon interactions and the Kondo effect in a FeSe/Sb2Te3/FeSe heterostructure: a proximity effect between ferromagnetic chalcogenide and di-chalcogenide
(Royal Society of Chemistry, 2022) Labanya Ghosh; Mohd Alam; Mahima Singh; Srishti Dixit; Satya Vijay Kumar; Abhineet Verma; Prashant Shahi; Yoshiya Uwatoko; Satyen Saha; Archana Tiwari; Ajay Tripathi; Sandip Chatterjee
In this report, we have introduced magnetic ordering into the nontrivial system of conventional topological insulators (TIs) by creating magnetic interfaces. In this context, antimony di-chalcogenide Sb2Te3 sandwiched between two thin layers of FeSe was prepared using the pulsed laser deposition (PLD) technique. The prepared heterostructure demonstrated good crystallinity along with homogeneous morphology displaying pyramid-shaped characteristic triangular islands. To comprehend the temperature and magnetic field modulated inter-layer properties of the prepared hetero-structure, transport, magneto-transport and magnetic properties were investigated. These properties establish the signature of the Kondo effect below 15 K, which has been attributed to the antiferromagnetic spin alignment in that temperature range. At around 150 K, longitudinal and transverse resistivity shows the metal-semiconductor transition, which was further elucidated through the anharmonic decay model in vibration phonon modes using Raman spectroscopy. Furthermore, a significant local spin evolution was explored at around 475 K by studying the magnetic properties of the system. The temperature dependency of the Raman modes confirmed the spin-phonon coupling initiated by local charge ordering at the proximity of the interface in the prepared hetero-structure. © 2022 The Royal Society of Chemistry.
Existence of exotic magnetic phases along with exchange bias and memory effect in frustrated beta-Mn Heusler alloy
(American Institute of Physics Inc., 2023) Srishti Dixit; Labanya Ghosh; Mohd Alam; Satya Vijay Kumar; Neha Patel; Swayangsiddha Ghosh; Nisha Shahi; Sanjay Singh; Sandip Chatterjee
Generally, Co-based Heusler alloys are the center of interest because of their properties such as high Curie temperature, spin polarization, and high value of exchange bias. Herein, we have used the macroscopic technique to probe the low-temperature exotic properties of M1.5Co0.5FeAl. First, we have analyzed the dc magnetization data, and it unfolds the presence of a glassy phase at 33 K. The cluster spin glass phase is authenticated by measuring ac susceptibility. Furthermore, using empirical models like power law and Vogel-Fulcher fitting, the relaxation time for the spin is of the order of τ ∼10-9 s, confirming the presence of a cluster spin glass in Mn1.5Co0.5FeAl below an irreversible temperature. The H-T phase space diagram ensures that it follows the Ising spin model. Furthermore, the glassy phase of the system is confirmed by magnetic relaxation, memory effect, and the presence of an exchange bias instead of a minor loop below spin-freezing temperature (TTf ~33 K). © 2023 Author(s).
Giant dielectric constant, magnetocaloric effect and spin-phonon coupling in EuTbCoMnO6 semiconductor
(Elsevier B.V., 2023) Mohd Alam; Labanya Ghosh; Srishti Dixit; Madhusmita Jena; Seema Kumari; Satya Vijay Kumar; Dheeraj Kumar; Abhineet Verma; A.K. Ghosh; Satyen Saha; R.J. Choudhary; Sandip Chatterjee
Transport, dielectric, magnetic and Raman studies of polycrystalline double perovskite EuTbCoMnO6 have been performed. Temperature-dependent resistivity follows the variable range and small polaron hopping mechanism. The temperature-dependent dielectric study shows the usual frequency-dependent step-like behavior. It also shows thermally activated relaxor peak in loss curves with giant dielectric constant near room temperature. The temperature-dependent magnetization demonstrates a second-order phase transition around 113 K. The critical behavior near the magnetic transition has been systematically investigated. The Widom scaling relation and magnetic entropy change calculation have verified the reliability of critical parameters. Maximum magnetic entropy change around the magnetic transition temperature shows the magnetocaloric effect. The estimated values of critical parameters are close to the value of the theoretical mean-field model. Temperature-dependent Raman study shows spin-phonon coupling in the system. The appearance of the magnetocaloric effect and colossal dielectric constant shows that these materials are interesting for real-life applications. © 2023 Elsevier B.V.
Lattice Dynamics of Bi1.9Dy0.1Te3 Topological Insulator
(Elsevier B.V., 2022) Labanya Ghosh; Vinod K. Gangwar; Mahima Singh; Satya Vijay Kumar; Srishti Dixit; Abhineet Verma; Durgesh Kumar Sharma; Sudhir Kumar; S. Saha; A.K. Ghosh; Sandip Chatterjee
In this report, we have investigated the Density functional theory (DFT) calculation, temperature-dependent thermoelectric power and Raman spectroscopy of Bi1.9Dy0.1Te3 topological insulator (TI). In this system, discrepancy due to the rare earth ion Dy initiates a Red-shift in Raman active modes in the Bi2Te3 TI. Here, the lattice thermal conductivity (κL) was evaluated in the Umklapp scattering limit using the temperature dependency of the vibrational phonon modes and was used to evaluate the Figure of merit (ZT) of the system. It has been demonstrated that the estimated Power factor and ZT is very large, confirming the efficiency of Bi1.9Dy0.1Te3 for better thermoelectric and electronic applications. Such immense thermoelectric power value of the corresponding system was further supported by the DFT calculation. © 2022
Multifunctional behaviour in B-site disordered double perovskite EuPrCoMnO6
(IOP Publishing Ltd, 2022) Mohd Alam; Labanya Ghosh; Supriyo Majumder; Prajyoti Singh; Satya Vijay Kumar; Srishti Dixit; Dheeraj Kumar; Khyati Anand; Seema Kumari; A.K. Ghosh; R.J. Choudhary; Sandip Chatterjee
We report magnetic, transport, dielectric, and complex impedance of polycrystalline double perovskite EuPrCoMnO6 which crystallizes in disordered orthorhombic phase with space group Pnma. The DC magnetization shows two successive ferromagnetic transitions around 146 K and 138 K. The temperature and magnetic field variation of DC-susceptibility suggest the existence of Griffith phase and spontaneous exchange bias. AC susceptibility measurement shows a glassy dynamic behaviour near ferromagnetic transition. Further, a re-entrant glassy dynamic state is seen at a low temperature around 40 K. Temperature-dependent resistivity shows semiconducting/insulating nature, which gets increased under the application of magnetic field, showing positive magnetoresistance. The dielectric study shows usual frequency-dependent step-like behaviour with a colossal dielectric constant near room temperature. The complex impedance study shows both grain and grain boundary contribute to the electrical properties. The observed properties suggest the material can be used for spintronic devices and high dielectric applications. © 2022 IOP Publishing Ltd.
Observation of the multiple magnetic phases in double perovskite Pr1.8La0.2CoFeO6
(Elsevier B.V., 2024) Dheeraj Kumar; Prajyoti Singh; Mohd Alam; Satya Vijay Kumar; Srishti Dixit; Krishanu Bandyopadhyay; G.D. Dwivedi; Satyen Saha; A.K. Ghosh; Sandip Chatterjee
The structural and magnetic properties of the double perovskite Pr1.8La0.2CoFeO6 have been investigated. The X-ray diffraction study shows that the system acquires room-temperature orthorhombic phase with the Pnma space group. The X-ray photoemission spectroscopy (XPS) measurement confirmed that the B-site ions are present in mixed valence states i.e. Co has been found in Co2+ and Co3+ valance states whereas Fe has been found in Fe3+/Fe4+. Magnetic measurements of the system confirm the existence of several fascinating magnetic behaviors, such as long-range canted antiferromagnetism withTN ∼ 271 K, giant exchange bias, and re-entrant cluster glass phase (TG ∼ 33 K). Field-dependent magnetization shows a large spontaneous exchange bias; HSEB∼ 1.8 kOe and giant conventional exchange bias, HCEB∼ 2.4 kOe at 5 K. Antiferromagnetic materials with large exchange bias can be utilized in high-density spintronic devices. Temperature-dependent Raman study demonstrates that the observed phonon mode exhibits anomalous behavior close to the magnetic transition temperature. Analysis of anomalous softening of phonon mode below TN, clarifies the presence of significant spin-phonon coupling while the magnetostriction effect does not play any significant role in the observed phonon anomaly. © 2024