http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/205 2025-11-04T06:45:46Z 2025-11-04T06:45:46Z Debnath, Anup http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/1109 2025-10-21T09:30:19Z 2021-02-04T00:00:00Z

Title: Ferromagnetic ordering in a THAB exfoliated WS2 nanosheet Authors: Debnath, Anup Abstract: Because of the important role of two-dimensional (2D) magnetic semiconductors in low-dimensional spintronic devices, the generation of ferromagnetism within an ultrathin semiconducting sheet of a transition metal dichalcogenide is highly desirable. A pristine WS2 sheet is a diamagnetic semiconducting transition metal dichalcogenide with superior electronic properties. In this study, we synthesised a free-standing WS2 sheet by a chemical route followed by electrochemical exfoliation by a giant molecule. During exfoliation of the WS2 crystal, atomic vacancies were created in the sheet with a lower number of layers. To understand the mechanism of exfoliation, we carried out x-ray diffraction, transmission electron microscopy, atomic force microscopy and Raman measurements. The types of atomic vacancies were realised by energy-dispersive x-ray spectroscopy, high-resolution transmission electron microscopy (fast Fourier transform), and x-ray photoelectron spectroscopy studies. We also observed a ferromagnetic ordering within the exfoliated WS2 sheet, which is explained on the basis of the generation of an atomic vacancy induced spin-moment. The transport study of the exfoliated WS2 sheet suggests that the electro-transport behaviour still remains as a semiconductor even after exfoliation. This ferromagnetic semiconducting system will be applicable in spintronic devices and this technique will enrich the literature, particularly for the preparation of a 2D semiconducting ferromagnet in a facile fashion.

2021-02-04T00:00:00Z Debnath, Anup http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/1108 2025-10-21T09:27:32Z 2024-05-29T00:00:00Z

Title: Giant enhancement of coercivity in β-Ni(OH)2 decorated Ti3C2Tx MXene nanosheets Authors: Debnath, Anup Abstract: Ti3C2Tx MXenes are of great interest due to their high conductivity, easy synthesis and unique functional properties. Functionalisation and structural engineering are essential for various applications because of their dramatic influences on different chemical and physical properties. Therefore, understanding the mechanism of the etching reaction of Ti3C2Tx from its parent MAX phase is crucial. The structural details also need to be understood for application in different practical devices. In this study, 2D Ti3C2Tx sheets with an average thickness of 3.48 nm and lateral dimension of 5.5 μm were synthesised by removing Al layers from the Ti3AlC2 MAX phase. The step-by-step etching mechanism was analysed with the help of Rietveld refinement of the powder x-ray diffraction data. The structural details and influence of different functional groups on the surface were also studied using transmission electron microscopy, x-ray photoelectron spectroscopy, and Raman spectroscopy. The magnetic behaviour and magnetic interaction of bare 2D Ti3C2Tx decorated with β-Ni(OH)2 nanosheets on its surface was studied. For the bare 2D Ti3C2Tx MXene sheets, a weak ferrimagnetic ordering with negligible coercivity was found. However, the β-Ni(OH)2-decorated Ti3C2Tx MXene sheets exhibit strong ferrimagnetic ordering with a sufficiently large coercivity of 0.2 T at 2 K and a transition temperature of 246 K. The generation of this interfacial ferrimagnetism is discussed in light of the interfacial charge transfer originating from d-p mixing. These 2D magnets generated at the interface could be useful for application in different spintronic devices.

2024-05-29T00:00:00Z Debnath, Anup http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/1107 2025-10-21T09:23:36Z 2017-12-26T00:00:00Z

Title: Observation of ferromagnetic ordering in a stable α-Co(OH)2 phase grown on a MoS2 surface Authors: Debnath, Anup Abstract: Because of the potential application of Co(OH)2 in a magnetic cooling system as a result of its superior magnetocaloric effect many people have investigated magnetic properties of Co(OH)2. Unfortunately, most of the works have been carried out on the β-Co(OH)2 phase due to the fact that the α-Co(OH)2 phase is very unstable and continuously transformed into the stable β-Co(OH)2 phase. However, in the present work, using a MoS2 sheet as a two-dimensional template, we have been able to synthesize a stable α-Co(OH)2 phase in addition to a β-Co(OH)2 phase by varying the layer thickness. It is seen that for thinner samples the β phase, while for thicker samples α phase, is grown on the MoS2 surface. Magnetic measurements are carried out for the samples over the temperature range from 2 to 300 K and it is seen that for the β phase, ferromagnetic ordering with fairly large coercivity (1271 Oe) at 2 K is obtained instead of the usual antiferromagnetism. The most interesting result is the observation of ferromagnetic ordering with a transition temperature (Curie temperature) more than 100 K in the α-Co(OH)2 phase. Complete saturation in the hysteresis curve under application of very low field having coercivity of ∼162 Oe at 2 K and 60 Oe at 50 K is obtained. A thin stable α-Co(OH)2 phase grown on MoS2 surface with very soft ferromagnetic ordering will be very useful as the core material in electromagnets.

2017-12-26T00:00:00Z Rai, Dibya Prakash http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/1048 2025-10-21T06:00:08Z 2021-08-12T00:00:00Z

Title: Enhanced H2 Storage Capacity of Bilayer Hexagonal Boron Nitride (h-BN) Incorporating van der Waals Interaction under an Applied External Electric Field Authors: Rai, Dibya Prakash Abstract: Lightweight two-dimensional materials are being studied for hydrogen storage applications due to their large surface area. The characteristics of hydrogen adsorption on the h-BN bilayer under the applied electric field were investigated. The overall storage capacity of the bilayer is 6.7 wt % from our theoretical calculation with Eads of 0.223 eV/H2. The desorption temperature to remove the adsorbed H2 molecules from the surface of the h-BN bilayer system in the absence of an external electric field is found to be ∼176 K. With the introduction of an external electric field, the Eads lies in the range of 0.223−0.846 eV/H2 and the desorption temperature is from 176 to 668 K. Our results show that the external electric field enhances the average adsorption energy as well as the desorption temperature and thus makes the h-BN bilayer a promising candidate for hydrogen storage.

2021-08-12T00:00:00Z