Anomalous Weak Ferromagnetism in Electron-doped Nd1−x Srx MnO3 (0.50 ≤ x ≤ 0.62) Thin Films

In the present work, we demonstrate that an anomalous weak ferromagnetism occurs in the composition range 0.50 <= x <= 0.62 in nanostructured thin films of Nd1-xSrxMnO3 (NSMO). Nanocrystalline thin films of overdoped manganite Nd1-xSrxMnO3 (x similar to 0.50, 0.55, 0.60, and 0.62) are grown on single-crystal LaAlO3 (001) substrates by using a nebulized chemical spray pyrolysis technique. These single phase films possess an average crystallite size similar to 15 nm, and the width of the grain boundaries is similar to 1 - 2 nm. In the composition range 0.50 <= x <= 0.62, the ground state of NSMO is an A-type antiferromagnetic (AFM) metallic state. However, in the present films, a broad paramagnetic (PM)-to-ferromagnetic (FM) transition is observed in all the compositions, at T-C similar to 226 K for x = 0.50 and at 235 K for rest of the samples. All the films show a well-defined M-H hysteresis loop at 5 K. The coercivity (H-C) of these films is much larger than those having compositions in the range 0.35 < x < 0.45. For x = 0.50 (0.62), the films H-C = -1210 (-1484) Oe and +1162 (+1476) Oe. The asymmetry in the coercivity suggests the presence of a weak exchange bias effect in these films. The FM ground state in these films is observed to have a smaller magnetic moment per Mn atom than the expected full moment from the rigid model; we term this as a weak ferromagnetic (WFM) state arising due to the destabilization of the AFM ordering. We propose a possible scenario based on the combined effect of spin reorganization and enhanced orbital disordering in nanosized manganites to explain the observed anomalous weak ferromagnetism in the A-type AFM spin ordered region

Prevalence of Hepatitis A Virus and Hepatitis E Virus Infection in the Patients Presenting with Acute Viral Hepatitis in Eastern India: A Cross-sectional Study

Introduction: Enterically transmitted Hepatitis A Virus (HAV) and Hepatitis E Virus (HEV) are the most common cause of Acute Viral Hepatitis (AVH) and a major health concern in developing nations like India. Both viruses cause AVH and are spread predominantly through the faecal-oral pathway, most commonly through contaminated water. Aim: To estimate the prevalence of HAV and HEV infection in patients presenting with AVH. Materials and Methods: An analytical cross-sectional study was undertaken in Indira Gandhi Institute of Medical Sciences, Bihar. The study was conducted over a period of 24 months from November 2019 to October 2021. All patients presenting with AVH were included as study participants. The blood samples were subjected to test anti-HAV and anti-HEV positivity. Prevalence of HAV and HEV was calculated taking total cases of AVH as denominator. Patients with confirmed infection with HCV, HBV and any other cause of hepatitis were excluded from the study. Templates were generated in an Microsoft Excel spreadsheet and analysis of data was done using Statistical Package of the Social Sciences software (SPSS) version 20.0. Quantitative data were presented as frequency and percentages. Results: A total of 682 patients presented with acute hepatitis. The AVH patients comprised 467 males (68.5%) and 215 (31.5%) females with the mean age 39.6±18.87 years. The current study reports the seroprevalence of 9.18% HAV and 8.35% of HEV. A total of 4 patients tested positive for coinfection with HAV and HEV. Most of the HAV patients belonged to an age group less than or equal to 12 years (25,58.1%) and none were more than 60 years. However, none of the HEV patients were children and most of them were aged between 13 to 60 years (46,92%). A male preponderance among HAV (28,65.1%), and HEV (38,76%) was noted. Conclusion: Low seroprevalence was noted, with infection more common in younger age group and male patients. Further studies and vaccination along with surveillance system strengthening are warranted

Impact of size mismatch induced quenched disorder on phase fluctuation and low field magnetotransport in polycrystalline Nd0.58−xGdxSr0.42MnO3

We report the magnetic and transport properties of polycrystalline Nd0.58−xGdxSr0.42MnO3 (x ∼ 0.0, 0.04, 0.08, 0.12, 0.16, 0.20, 0.25, 0.30, 0.35, and 0.42). All the samples are single phase and have grain size ∼ 1–2 μm. As the variance σ2 increases, the paramagnetic-ferromagnetic transition shows a gradual decrease and broadening, while the decrease in insulator metal transition is sharpened. However, near equality of TC and TIM at intermediate values of σ2 could be understood in terms of the competing quenched and the grain boundary disorder. The variation in peak magnetoresistance (MR) (maximum MR around TC/TIM) with σ2 shows that maximum low field MR ≈ 35% at H = 3 kOe (68% at H = 10 kOe) is centered around σ2 = 0.009 857 Å2 (x = 0.25). This shows that huge intrinsic MR can be obtained at relatively higher temperatures and lower magnetic fields in the region of enhanced phase fluctuations

Thickness dependent transport properties of compressively strained La0.88Sr0.12MnO3 ultrathin films

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Thickness dependent transport properties of compressively strained La0.88Sr0.12MnO3 ultrathin films

Thickness dependent magnetic and transport properties of compressively strained La0.88Sr0.12MnO3 thin films grown on single crystalline SrTiO3 (100) substrates have been studied. All films exhibit a large enhancement of ∼130 K in TC/TIM as compared to that of the bulk target (TC∼175 K). This has been explained in terms of suppression of the cooperative Jahn–Teller distortion due to in-plane compressive strain. The TC/TIM of the 5 nm film is 315 K/318 K and slightly increases for film thicknesses ≤25 nm. At higher film thicknesses, ∼60 nm, the TC/TIM starts decreasing. At T>TIM, the electrical transport is due to thermally activated hopping of small polarons. The activation energy is found to be sensitive to film thickness and shows a minimum at around L∼15–25 nm, which corresponds to the maximum of TC/TIM. All films possess large magnetoresistances (MRs) in the vicinity of room temperature. Low as well as high field MRs are observed to nearly double as the film thickness increases from 5 nm (MR∼28%/3 T) to 60 nm (MR%∼50%/3 T). Thicker films (L≥25 nm) are found to exhibit sufficiently large temperature coefficients of resistivities, ∼4%–5%/K, which could be suitable for bolometric applications

Comparative study of transport properties of compressively strained epitaxial and polycrystalline La0.88Sr0.12MnO3 thin films

We report a comparative study of the magnetoelectrical properties of epitaxial and polycrystalline thin films of lightly doped manganite La0.88Sr0.12MnO3 (LSMO). The LSMO thin films are deposited on single-crystal LaAlO3 (LAO/(100)) and yttria-stabilized ZrO2 (ZO/(100)) substrates by on-axis DC magnetron sputtering from high-density targets prepared by a wet chemical route. Films deposited on LAO (6 nm and 35 nm thick) are epitaxial and AFM investigations show clean surface morphology. In contrast, films on ZO (20 nm and 35 nm) are polycrystalline. Small variation in grain size is seen in the surface morphology of films on ZO. Both 6 nm and 35 nm thick films on LAO show sharp I–M transitions around the TC with TIM being 275 K and 285 K, respectively. The TIM of films on ZO is drastically suppressed as compared to the same for films on LAO. The large enhancement in TC and hence TIM of LSMO films on LAO has been explained in terms of the compressive strain arising due to the mismatch between the lattice parameters of LAO and LSMO. The absence of such strain in LSMO films on ZO accounts for the lower TIM values. The LSMO/LAO films also show large magnetoresistance only in the vicinity of the TIM and it decreases strongly on lowering and increasing the temperature. In contrast, the LSMO/ ZO films show relatively lower MR spreading over a wider temperature range. The electrical transport of all the films, both in the PM as well as the FM regions have been analyzed in the framework of several models and the suitability of each model has been discussed. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Comparative study of transport properties of compressively strained epitaxial and polycrystalline La 0.88 Sr 0.12 MnO 3 thin films

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Enhanced magneto-electrical properties and room temperature magnetoresistance in lightly doped manganite thin films

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