Browsing by Author "Mahima Singh"

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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.
Anomalous Hall effect in Cu doped Bi2Te3 topological insulator
(Institute of Physics Publishing, 2020) Abhishek Singh; Shiv Kumar; Mahima Singh; Prajyoti Singh; Rahul Singh; Vinod K Gangwar; Archana Lakhani; Swapnil Patil; Eike F Schwier; Takeshi Matsumura; K. Shimada; A.K. Ghosh; Sandip Chatterjee
The angle resolved photo-emission spectroscopy (ARPES) study and magneto-transport properties of Bi2CuxTe3-x have been investigated. ARPES study indicates the clear existence of surface states in the as-prepared samples. The estimated bandgap from ARPES is found to be ∼5 meV and 16 meV respectively for x = 0.03 and x = 0.15 samples. Presence of larger Cu concentration (x = 0.15) introduces magnetic ordering. Observed non-linearity in the Hall data is due to the existence of anomalous Hall effect which can be attributed to the 2D transport. The observed magneto-transport features might be related to the surface carriers which is confirmed by ARPES study. © 2020 IOP Publishing Ltd.
Correlation between changeover from weak antilocalization (WAL) to weak localization (WL) and positive to negative magnetoresistance in S-doped Bi1.5Sb0.5Te1.3Se1.7
(American Institute of Physics Inc., 2022) Mahima Singh; Labanya Ghosh; Vinod K. Gangwar; Yogendra Kumar; Debarati Pal; P. Shahi; Shiv Kumar; Sudip Mukherjee; K. Shimada; Sandip Chatterjee
The magneto-transport and angle-resolved photoelectron spectroscopy (ARPES) of the S-doped Bi1.5Sb0.5Te1.3Se1.7 system have been investigated. Both the positive magnetoresistance (pMR) and negative magnetoresistance (nMR) under a perpendicular magnetic field as well as a changeover from weak antilocalization (WAL) to weak localization (WL) are observed. The interplay between pMR and nMR is elucidated in terms of the dephasing and spin-orbit scattering time scales. The topological surface state bands have been explored using ARPES. © 2022 Author(s).
Defect induced ferromagnetic ordering and room temperature negative magnetoresistance in MoTeP
(NLM (Medline), 2021) Debarati Pal; Shiv Kumar; Prashant Shahi; Sambhab Dan; Abhineet Verma; Vinod K. Gangwar; Mahima Singh; Sujoy Chakravarty; Yoshiya Uwatoko; Satyen Saha; Swapnil Patil; Sandip Chatterjee
The magneto-transport, magnetization and theoretical electronic-structure have been investigated on type-II Weyl semimetallic MoTeP. The ferromagnetic ordering is observed in the studied sample and it has been shown that the observed magnetic ordering is due to the defect states. It has also been demonstrated that the presence of ferromagnetic ordering in effect suppresses the magnetoresistance (MR) significantly. Interestingly, a change-over from positive to negative MR is observed at higher temperature which has been attributed to the dominance of spin scattering suppression.
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
Reentrant double glassy states and simultaneous presence of short- and long-range ordering in metamagnetic Co-doped Bi0·5La0·5Fe0·5Mn0·5O3 multiferroic
(Elsevier Masson s.r.l., 2022) Prince K. Gupta; Khyati Anand; Mohd Alam; Surajit Ghosh; Seema Kumari; Arkadeb Pal; Mahima Singh; K.K. Shukla; Peter Tsung-Wen Yen; Shin-Ming Huang; A.K. Ghosh; Sandip Chatterjee
A study of the structural and magnetic properties of Bi0·5La0·5Fe0·45Co0·05Mn0·5O3 is presented in the article. We report the rare observations of two glassy transitions below the long-range ordering temperature along with the metamagnetic transitions at low temperatures. Frequency and DC field dependence of AC susceptibility and isothermal relaxation of remnant magnetization studies have all shown the slow spin dynamics for the compound. Interestingly, in the glass phase of the materials, metamagnetic transitions of the antiferromagnetic spins were found which indicate the coexistence of the long-range ordered phase along with the short-range ordered glassy phase. The double cluster glass phases can be comprehended, from the relaxations of the spin clusters arising from the competing magnetic interactions present in the system. Moreover, the roles of additional exchange interactions which are brought to the system by Co doping are also considered in explaining the observed double cluster glass transitions. © 2022 Elsevier Masson SAS
Roles of surface and bulk states in giant magnetoresistance and anomalous hall effect in antiferromagnetically ordered Bi1.9Dy0.1Te3 topological insulators
(Royal Society of Chemistry, 2022) Vinod K. Gangwar; Shiv Kumar; Mahima Singh; Debarati Pal; Labanya Ghosh; Prajyoti Singh; Zhang Yufeng; Chaoyu Chen; Eike F. Schwier; Kenya Shimada; Prashant Shahi; Yoshiya Uwatoko; Swapnil Patil; Anup K. Ghosh; Sandip Chatterjee
A wide variety of emerging spintronic device concepts will greatly benefit from the use of materials with an anomalous Hall effect and large magnetoresistance. In this regard, a magnetic topological insulator is a potential candidate, leading to a better way to manipulate spin. The different roles of surface and bulk states in Bi1.9Dy0.1Te3 topological insulators are determined by investigating electronic states, magnetotransport properties, Seebeck coefficient and magnetization. Magnetoresistance attains a huge value ∼1500% at a magnetic field of 7 T, which is attributed to the surface state. The magnetization behavior clearly suggests the existence of an antiferromagnetic state. The observed anomalous Hall effect is established as the contribution from the bulk state. Furthermore, it is demonstrated that there is no appreciable energy gap at the Dirac point of the topological surface. © 2022 The Royal Society of Chemistry.