Browsing by Author "Yoshiya Uwatoko"

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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.
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
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.
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.