Browsing by Author "K. Mukherjee"

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Atomic disorder and Berry phase driven anomalous Hall effect in a Co2FeAl Heusler compound
(American Physical Society, 2022) Gaurav K. Shukla; Ajit K. Jena; Nisha Shahi; K.K. Dubey; Indu Rajput; Sonali Baral; Kavita Yadav; K. Mukherjee; Archana Lakhani; Karel Carva; Seung-Cheol Lee; Satadeep Bhattacharjee; Sanjay Singh
Co2-based Heusler compounds are promising materials for spintronics applications due to their high Curie temperature, large spin polarization, large magnetization density, and exotic transport properties. In the present paper, we report the anomalous Hall effect (AHE) in a polycrystalline Co2FeAl Heusler compound using combined experimental and theoretical studies. The Rietveld analysis of high-resolution synchrotron x-ray diffraction data reveals a large degree (∼50%) of antisite disorder between Fe and Al atoms. The analysis of anomalous transport data provides the experimental anomalous Hall conductivity (AHC) about 227 S/cm at 2 K with an intrinsic contribution of 155 S/cm, which has nearly constant variation with temperature. The detailed scaling analysis of anomalous Hall resistivity suggests that the AHE in Co2FeAl is governed by the Berry phase driven intrinsic mechanism. Our theoretical calculations reveal that the disorder present in the Co2FeAl compound enhances the Berry curvature induced intrinsic AHC. © 2022 American Physical Society.
Emergence of a partially disordered magnetic state driven by structural distortion in P d2DySn
(American Physical Society, 2025) P. Koushik; Manisha Choudhary; Vishal Kumar; Sanjay Singh; K. Mukherjee
Frustrated magnetism, driven by competing exchange interactions, remains a pivotal topic in modern condensed-matter physics. In frustrated systems, observation of a partially disordered (PD) state where long-range magnetic order coexists with disorder is a unique phenomenon. Here, we focus on the emergence of a PD state and its underlying mechanism in a Heusler alloy, Pd2DySn. Our findings reveal that this alloy crystallizes in a cubic structure and undergoes a partial transformation to tetragonal phase at low temperatures. The static magnetization and heat capacity studies reveal three successive long-ranged antiferromagnetic transitions at ∼16, 12, and 6 K, respectively, while dynamic magnetization studies provide clear evidence for multiple cluster glass transitions, concomitant with the long-range ordering temperatures. This study demonstrates the coexistence between antiferromagnetic and glassy magnetic states, which is a relatively rare phenomenon in Heusler alloys. We propose that the emergence of the PD state stems from magnetic frustration induced by the structural distortion rather than geometrical frustration associated with triangular networks of magnetic ions as observed in other PD magnetic systems. © 2025 American Physical Society.
Investigation of lymphocyte subpopulations and hypersensitivity skin tests during the menstrual cycle and pregnancy
(1982) S. Agarwal; H.S. Shukla; M. Verma; S.C. Gupta; K. Mukherjee
Cell-mediated immune responses were examined during the menstrual cycle of 10 healthy females and in 90 pregnant females, 10 for each month of gestation, and in 10 females 2-4 weeks after normal delivery. Lymphocytes and their subpopulations and PPD hypersensitivity skin tests were investigated. The lymphocyte subpopulation T-cells showed statistically significant depression at the time of ovulation (P < 0.01) and during the entire period of gestation (P < 0.001) with recovery in the post-partum period. There was borderline PPD skin response during pregnancy which became positive after parturition. These changes were demonstrated to be specific to conception but the exact mechanism of the T-cell depression is not known. There was a corresponding rise in the B-cell count.
Sequential radiation changes in cytology of vaginal smears in carcinoma of cervix uteri during radiotherapy
(1987) S. Gupta; K. Mukherjee; Y.N. Gupta; M. Kumar
The study deals with acute/immediate radiation changes in 2020 sequential vaginal smears in 101 patients of carcinoma of the cervix uteri, 97 were of squamous cell carcinoma and 4 of adenocarcinoma. The smears were collected after 12-14 days, 15-24 days and 25 days to 6 weeks following radiotherapy. The pretreatment vaginal smears were collected and examined for percentage of cancer cells. Subsequent smears were studied for radiation changes in benign and malignant cells, such as cell size, vacuolation of cytoplasm, multinucleation and nuclear changes, etc. A gradual and linear decline in cancer cells was observed until the end of therapy; 41.6% of patients had less than 10% cancer cells within 12-14 days of therapy, 63.4% of patients between 15 and 24 days and 74.6% after 25 days to 6 weeks following radiation. Eighty three percent of the patients attained zero level at the end of therapy. © 1987.