Browsing by Author "S. Rastogi"

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Preparation of Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O superconducting films by conventional techniques
(Springer India, 1991) K.K. Verma; A.K. Saxena; S. Rastogi; R.S. Tiwari; O.N. Srivastava
High temperature superconducting films of Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O have been deposited on different substrates using conventional techniques, like flash evaporation and spray pyrolysis. The microstructural investigation of the films by SEM technique reveals the partially oriented nature of the crystallites. In the case of spray-deposited Bi-Sr-Ca-Cu-O HTSC films it has been found that film/substrate mismatch is not the decisive factor for the superconducting transition temperature T c. © 1991 Indian Academy of Sciences.
Pressure driven iso-structural phase transition and its implication on the Néel skyrmion host hexagonal PtMnGa
(American Physical Society, 2024) K.K. Dubey; S. Rastogi; Ajit K. Jena; Gaurav K. Shukla; Parul Devi; Seung-Cheol Lee; Satadeep Bhattacharjee; R. Rawat; Boby Joseph; Sanjay Singh
Magnetic skyrmions are nanometer-sized whirling spin textures in the magnetic material, which have the potential to revolutionize the field of spintronics. This study explores the influence of pressure on the structural properties of the PtMnGa hexagonal system, recognized for hosting Néel skyrmions. By employing pressure-dependent synchrotron x-ray powder diffraction (SXRPD), we reveal an isostructural phase transition in this system at approximately 6 GPa. The isostructural transition is evidenced by a deviation of the lattice parameter from the linear dependence, change of trend in the in-plane to out-of-plane lattice parameter ratio, and a description of the pressure-unit cell volume data by two distinct second-order Birch-Muraghan equation of states. The PtMnGa system, however, exhibits reversible structural behavior when pressure is released. Analysis of combined pressure and temperature-dependent SXRPD data provides indirect evidence that the application of moderate pressure (0.8-1.09 GPa) shifts the thermodynamically stable skyrmion regime near to room temperature in the Néel skyrmion-host PtMnGa system. Theoretical calculations on band structure, magnetic moment, and density of states (DOS) under pressure further corroborate the experimental findings, offering a comprehensive understanding of the material's response to pressure changes. The combination of experimental findings and theoretical calculations demonstrates the potential for engineering materials supporting stable skyrmions even at elevated temperatures and nominal pressures, which can be attained in the materials using chemical substitution or epitaxial thin films by strain controlling of the substrate-film lattice parameter mismatch. © 2024 American Physical Society.