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Coexistence of superconductivity and ferromagnetism in Sr_0.5Ce_0.5FBiS_2-xSe_x (x = 0.5 and 1.0), a non-U material with T_c < T_FM.

ABSTRACT: We have carried out detailed magnetic and transport studies of the new Sr_0.5Ce_0.5FBiS_2-xSe_x (0.0 ≤ x ≤ 1.0) superconductors derived by doping Se in Sr_0.5Ce_0.5FBiS₂. Se-doping produces several effects: it suppresses semiconducting-like behavior observed in the undoped Sr_0.5Ce_0.5FBiS₂, the ferromagnetic ordering temperature, T_FM, decreases considerably from 7.5 K (in Sr_0.5Ce_0.5FBiS₂) to 3.5 K and the superconducting transition temperature, T_c, gets enhanced slightly to 2.9-3.3 K. Thus in these Se-doped materials, T_FM is marginally higher than T_c. Magnetization studies provide evidence of bulk superconductivity in Sr_0.5Ce_0.5FBiS_2-xSe_x at x ≥ 0.5 in contrast to the undoped Sr_0.5Ce_0.5FBiS₂ (x = 0) where magnetization measurements indicate a small superconducting volume fraction. Quite remarkably, as compared with the effective paramagnetic Ce-moment (~2.2 μ_B), the ferromagnetically ordered Ce-moment in the superconducting state is rather small (~0.1 μ_B) suggesting itinerant ferromagnetism. To the best of our knowledge, Sr_0.5Ce_0.5FBiS_2-x Se_x (_x = 0.5 and 1.0) are distinctive Ce-based bulk superconducting itinerant ferromagnetic materials with T_c < T_FM. Furthermore, a novel feature of these materials is that they exhibit a dual and quite unusual hysteresis loop corresponding to both the ferromagnetism and the coexisting bulk superconductivity.

SUBMITTER: Thakur GS

PROVIDER: S-EPMC5124956 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The antioxidant therapy to preserve residual hearing is relatively recent, and the search for effective antioxidants is still ongoing. Though nanoceria has shown promising radical-scavenging capability, improving its antioxidant ability and the dispersion stability of its nanofluid, which is critical to the desired site, i.e., cochlea, still remains a major challenge. The objective of the present work is to study the radical-scavenging capability of poly(ethylene glycol) (PEG)-coated CeO2 and Ce0.5Zr0.5O2 nanoparticles in water and the biologically relevant fluid (PBS buffer). Nanoparticles in the size range of 4.0-9.0 nm are synthesized using the coprecipitation method and characterized using suitable techniques. The scavenging and dispersion stability of the synthesized nanofluid are analyzed using a UV-vis spectrophotometer. It is found that the addition of PEG during the synthesis process promoted the generation of finer nanoparticles with a narrow size distribution and the doping of zirconium produced a large number of defects in the crystallite structure. The PEG coating over the nanoparticles improved the dispersion stability of nanofluids without affecting their surface reactivity, and it is found to be 94 and 80% in water and PBS, respectively, at 500 μM and 60 min, which is maintained till 90 min. The highest scavenging of hydroxyl radicals by PEG-coated Ce0.5Zr0.5O2 is found to be 60%, which is significantly superior to that of CeO2. The scavenging capability is found to be increased with the concentration of nanoparticles, showing the best scavenging activity at 190 and 150 μM for PEG-coated CeO2 and Ce0.5Zr0.5O2, respectively, and the scavenging in water is at par with that of PBS, indicating that these nanoparticles are suitable to be used in sites where a biologically relevant fluid is present, e.g., the cochlea. It is proposed that PEG-coated Ce0.5Zr0.5O2 having an average size of ∼ 4 nm can be a potential antioxidant in relevant biomedical applications.

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Coexistence of superconductivity and ferromagnetism in Sr_0.5Ce_0.5FBiS_2-xSe_x (x = 0.5 and 1.0), a non-U material with T_c < T_FM.

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Coexistence of superconductivity and ferromagnetism in Sr0.5Ce0.5FBiS2-xSex (x = 0.5 and 1.0), a non-U material with Tc < TFM.

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Coexistence of superconductivity and ferromagnetism in Sr_0.5Ce_0.5FBiS_2-xSe_x (x = 0.5 and 1.0), a non-U material with T_c < T_FM.