Browsing by Author "Manoranjan Kumar"

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Anomalous Hall effect from gapped nodal line in the Co2FeGe Heusler compound
(American Physical Society, 2021) Gaurav K. Shukla; Jyotirmoy Sau; Nisha Shahi; Anupam K. Singh; Manoranjan Kumar; Sanjay Singh
Full Heusler compounds with cobalt as a primary element show anomalous transport properties owing to the Weyl fermions and broken time-reversal symmetry. We present here the study of anomalous Hall effect (AHE) in the Co2FeGe Heusler compound. The experiment reveals anomalous Hall conductivity (AHC) ∼100 S/cm at room temperature with an intrinsic contribution of ∼78 S/cm. The analysis of anomalous Hall resistivity suggests the scattering independent intrinsic mechanism dominates the overall behavior of anomalous Hall resistivity. The first principles calculation reveals that the Berry curvature originated by a gapped nodal line near EF is the main source of AHE in the Co2FeGe Heusler compound. The theoretically calculated AHC is in agreement with the experiment. © 2021 American Physical Society.
B-site disorder driven multiple-magnetic phases: Griffiths phase, re-entrant cluster glass, and exchange bias in Pr2CoFeO6
(American Institute of Physics Inc., 2019) Arkadeb Pal; Prajyoti Singh; V.K. Gangwar; Surajit Ghosh; P. Prakash; S.K. Saha; Amitabh Das; Manoranjan Kumar; A.K. Ghosh; Sandip Chatterjee
The magnetic spin ordering and the magnetization dynamics of a double perovskite Pr2CoFeO6 have been investigated by employing the (dc and ac) magnetization and neutron powder diffraction techniques. The study revealed that Pr2CoFeO6 adopted a B-site disordered orthorhombic structure (Pnma). Furthermore, ab initio band structure calculations suggested an insulating antiferromagnetic ground state. Magnetization measurements revealed that the system possesses a spectrum of competing magnetic phases, viz., long range canted antiferromagnetic (AFM) spin ordering (TN ∼269 K), Griffiths-like phase, re-entrant cluster glass (TG ∼34 K), and exchange bias effects. The neutron diffraction study divulged the exhibition of a long range G-type of canted AFM spin ordering. The random nonmagnetic dilution of magnetic Fe3+ (high spin) ions by Co3+ (low spin) ions due to B-site disorder essentially played a crucial role in manifesting such magnetic properties of the system. © 2019 Author(s).
Hydrostatic pressure-induced anomalous hall effect in Co2FeSi semimetal
(Institute of Physics, 2024) Jyotirmoy Sau; Debanand Sa; Manoranjan Kumar
The Weyl points and nodal line emerge in the momentum space due to symmetry protected state in topological semimetal materials and these materials hold significance due to their unusual anomalous transport properties. In this manuscript, we study the topological properties of the electronic band structure of a half-metallic ferromagnet Co2FeSi employing the ab-initio density functional theory method and show that it is a strongly correlated material. The experimentally observed magnetic properties can be explained in terms of the Slater-Pauling (SP) rule and our calculations are consistent with it. We also investigate the band topology of Co2FeSi and find that there are three topological nodal lines at 380 meV above Fermi Energy (E F ). The degeneracy of these nodal lines is perturbed upon introducing spin-orbit coupling with magnetization along [001] direction. However, some points still preserve degeneracy and are identified as Weyl points, each associated with a specific Chern number. At the ambient pressure, the AHC properties of this material have only extrinsic contribution which is consistent with the experimental results. To make the AHC intrinsic, we tune the position of the nodal line close to the Fermi energy by applying the hydrostatic pressure up to 26 GPa. We also discuss crystal symmetries and their relation with nodal lines and Weyl points. © 2024 IOP Publishing Ltd.
Modelling water levels of northwestern India in response to improved irrigation use efficiency
(Nature Research, 2020) Shashank Shekhar; Suman Kumar; A.L. Densmore; W.M. van Dijk; Rajiv Sinha; Manoranjan Kumar; Suneel Kumar Joshi; Shive Prakash Rai; Dewashish Kumar
The groundwater crisis in northwestern India is the result of over-exploitation of groundwater resources for irrigation. The Government of India has targeted a 20 percent improvement in irrigation groundwater use efficiency. In this perspective, and using a regional-scale calibrated and validated three-dimensional groundwater flow model, this article provides the first forecasts of water levels in the study area up to the year 2028, both with and without this improvement in use efficiency. Future water levels without any mitigation efforts are anticipated to decline by up to 2.8 m/year in some areas. A simulation with a 20 percent reduction in groundwater abstraction shows spatially varied aquifer responses. Tangible results are visible in a decade, and the water-level decline rates decrease by 36–67 percent in over-exploited areas. Although increasing irrigation use efficiency provides tangible benefits, an integrated approach to agricultural water management practice that incorporates use efficiency along with other measures like water-efficient cropping patterns and rainwater harvesting may yield better results in a shorter period. © 2020, The Author(s).
Unusual negative magnetoresistance in Bi2Se3-ySy topological insulator under perpendicular magnetic field
(American Institute of Physics Inc., 2018) Rahul Singh; Vinod K. Gangwar; D.D. Daga; Abhishek Singh; A.K. Ghosh; Manoranjan Kumar; A. Lakhani; Rajeev Singh; Sandip Chatterjee
The magneto-transport properties of Bi2Se3-ySy were investigated. Magnetoresistance (MR) decreases with an increase in the S content, and finally, for 7% (i.e., y = 0.21) S doping, the magnetoresistance becomes negative. This negative MR is unusual as it is observed when a magnetic field is applied in the perpendicular direction to the plane of the sample. The magneto-transport behavior shows the Shubnikov-de Haas (SdH) oscillation, indicating the coexistence of surface and bulk states. The negative MR has been attributed to the non-trivial bulk conduction. © 2018 Author(s).