Browsing by Author "Swayangsiddha Ghosh"

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Coexistence of Kondo effect and non trivial Berry phase in Gd doped Bi2Se3: an ARPES and magneto-transport study
(Institute of Physics, 2025) Swayangsiddha Ghosh; Rahul Kunwar Singh; Srishti Dixit; Shiv Kumar; Yogendra Kumar; Kenya Shimada; Anup Kumar Ghosh; Archana Lakhani; Sandip Chatterjee
The presence of magnetic impurities in topological insulators can disrupt their time reversal symmetry and lead to the emergence of an energy gap. This study delves into the energy band structure and the Kondo effect through the introduction of Gadolinium (Gd) magnetic perturbations (at levels of x = 0.1 , 0.16 ) into a pure Bi2Se3 single crystal. In the case of the Bi1.9Gd0.1Se3 (5%) single crystal, the Kondo effect becomes observable at temperatures below 50 K. However, the unaltered parent and Bi1.84Gd0.16Se3 (8%) exhibit typical metallic behavior. The pure sample displays the highest magnetoresistance (MR) of around 225% and demonstrates quantum oscillations driven by a nontrivial berry phase. The sample doped with 5% Gd undergoes a transition from negative MR to positive MR due to a presence of mixed magnetic state resulting from the opening of a gap at the Dirac point. This gap opening is confirmed through angle-resolved photoemission spectroscopy (ARPES) measurements. The comparison of the parameters obtained from the SdH and ARPES measurements, the reduction in the k F values in the magnetotransport measurements is likely due to the band bending induced by the Schottky barrier. Thermoelectric properties are assessed across all prepared samples. The undoped sample displays the highest Seebeck coefficient and power factor values of − 398.02 μ V K − 1 and 6.83 mW mK − 2 , respectively, at room temperature. These values are notably high for thermoelectric applications at room temperature. © 2025 IOP Publishing Ltd. All rights, including for text and data mining, AI training, and similar technologies, are reserved.
Coexistence of Kondo effect and Weak anti-localization in Topological insulator/Ferromagnetic heterostructure
(Elsevier B.V., 2024) Labanya Ghosh; Swayangsiddha Ghosh; Srishti Dixit; Mohd Alam; Neha Patel; Archana Tiwari; Prashant Shahi; Yoshiya Uwatoko; Sandip Chatterjee
The presence of a magnetic impurity in a topological insulator weakens the time-reversal symmetry by creating a limited gap at the Dirac point, and could result in the creation of new quantum states. On the other hand, causing magnetization in a topological insulator through the interlayer proximity effect to a magnetically ordered system is a better choice, as magnetic doping may have negative effects. In this report, the magnetic and magneto-transport properties of FeSe intercalated Bi2Se3 crystals and FeSe/Bi2Se3/FeSe hetero-structure have been investigated. The XPS depth profile was studied to confirm the layered structure of the hetero-structure. The weak anti-localization state in the multilayer system has been seen to coexist with the Kondo effect, which may have caused by the interfacial magnetic domains modifying the electronic characteristics at interfaces. Such magnetic spin-induced inter-layer coupling can be a pathway to room-temperature spintronic applications. © 2024
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).
Raman effect and unusual transport properties of Co-doped Mn2FeAl Heusler alloy
(Institute of Physics, 2023) Srishti Dixit; Swayangsiddha Ghosh; Neha Patel; Mohd Alam; Krishanu Bandyopadhyay; Nisha Shahi; Yogendra Kumar; M. Sawada; K. Shimada; Satyen Saha; Sanjay Singh; Sandip Chatterjee
Semiconducting materials with a distinctive blend of high electrical and low thermal conductivity are required for efficient thermoelectric devices. In this aspect, Heusler alloys are potential candidates for thermoelectric materials. It has been observed that Co doping in Mn2FeAl enhances the electrical conductivity as well as reduces the thermal conductivity of the system leading to an improvement in figure of merit. The Seebeck coefficient suggested the p-type behavior over the whole temperature range, followed by a maximum at 150 K. Additionally, the electronic properties of the suggest that the observed Raman mode is due to the electronic excitations in the system. Interestingly, this system shows a decoupling between the Seebeck coefficient and electrical conductivity, suggesting the promising potential of as a thermoelectric material and offering valuable insights into its electronic properties. Copyright © 2024 EPLA.
Spontaneous exchange bias and large dielectric constant in Bi0.8Tb0.2Fe0.8Mn0.2O3multiferroic
(American Institute of Physics Inc., 2022) Seema Kumari; Khyati Anand; Mohd Alam; Labanya Ghosh; Swayangsiddha Ghosh; Prince Gupta; Rahul Singh; A.K. Jain; S.M. Yusuf; Anup K. Ghosh; Anita Mohan; Sandip Chatterjee
The structural, dielectric, and magnetic properties of Bi0.8Tb0.2Fe0.8Mn0.2O3 have been studied in detail. A structural shift from rhombohedral (space group R3c) to orthorhombic (space group Pn21a + Pnma) phase is observed with doping. The substitution of Mn and Tb gives a very large value of the dielectric constant. It has been demonstrated that the observed spontaneous exchange bias is larger than the conventional exchange bias at room temperature. Moreover, doping reduces the Neel temperature from 643 to 521 K and magnetization increases. Thermoremanent magnetization studies at room temperature show that the system is composed of an interfacial layer of an antiferromagnetic core and a two-dimensional diluted antiferromagnet shell with a net magnetization under the field. Furthermore, the system's reasonable HEB and HC values at room temperature make it intriguing and appealing for a variety of multifunctional devices. © 2022 Author(s).