Charge order suppression and antiferromagnetic to ferromagnetic switch over in Pr_0.5Ca_0.5MnO_3 nanowires

We have prepared crystalline nanowires (diameter ~ 50 nm, length ~ a few microns) of the charge ordering manganite Pr_0.5Ca_0.5Mn_O3 using a low reaction temperature hydrothermal method and characterized them using X-ray diffraction, transmission electron microscopy, SQUID magnetometry and electron magnetic resonance measurements. While the bulk sample shows a charge ordering transition at 245 K and an antiferromagnetic transition at 175 K, SQUID magnetometry and electron magnetic resonance experiments reveal that in the nanowires phase, a ferromagnetic transition occurs at ~ 105 K. Further, the antiferromagnetic transition disappears and the charge ordering transition is suppressed. This result is particularly significant since the charge order in Pr_0.5Ca_0.5MnO_3 is known to be very robust, magnetic fields as high as 27 T being needed to melt it.Comment: 12 pages including 4 figures. submitted to Applied Physics Letter

An anomalous magnetic phase transition at 10 K in Nd7Rh3

The compound, Nd7Rh3, crystallizing in Th7Fe3-type hexagonal structure, has been shown recently by us to exhibit a signature of magnetic phase-coexistence phenomenon below 10 K after a field cycling, uncharacteristic of stoichiometric intermetallic compounds, bearing a relevance to the trends in the field of electronic phase-separation. In order to characterize this compound further, we have carried out dc magnetic susceptibility (chi), electrical resistivity, magnetoresistance and heat-capacity measurements as a function temperature (T= 1.8 to 300 K). The results reveal that this compound exhibits another unusual finding at the 10K-transition in the sense that the plot of chi(T) shows a sharp increase in the field-cooled cycle, whereas the zero-field-cooled curve shows a downturn below the transition. In addition, the sign of magnetoresistance is negative and the magnitude is large over a wide temperature range in the vicinity of magnetic ordering temperature, with a sharp variation at 10 K. The results indicate that the transition below 10 K is first-order in its character.Comment: Appeared in JPCM (Letters) 18 (2006) L40

Catalytic activity of nickel ferrite nanoparticles in synthesis of 4-aryl benzelidene-2- ((5-fluoro-1H-indol-1-yl)methyl)oxazol-5(4H)-one and its evalute the biological activity

ABSTRACT. Seven 4-arylbenzelidene-2-((5-fluoro-1H-indol-1-yl)methyl)oxazol-5(4H)-one derivatives were synthesized by the condensation of 2-(2-(5-fluoro-1H-indol-1-yl) acetoamide) acetic acid, substituted aromatic aldehydes with acetic anhydride and sodium acetate in the presence of MgO/Al2O3 under reflux using nickel ferrite nanoparticles. Seven of the compounds are new derivatives. 2-(2-(5-fluoro-1H-indol-1-yl)acetoamide) acetic acid was obtained from 2-(5-fluoro-1H-indol-1-yl)acetyl chloride with lysine in the presence of NaOH and HCl in the ice cold solution. 2-(5-fluoro-1H-indol-1-yl)acetyl chloride can be prepared from 5-fluoro indole with chloroacetyl chloride in triethylamine and dichloromethane. The structures of the compounds were evaluated based on 1H-NMR, 13C-NMR and LC-MS and by elemental analysis. These compounds were screened by anti-oxidant as well as anti-microbial activity.               KEY WORDS: 2-(5-Fluoro-1H-indol-1-yl)acetyl chloride, 2-(2-(5-Fluoro-1H-indol-1-yl)acetoamide) acetic acid, 4-Aryl Benzelidene-2-((5-fluoro-1H-indol-1-yl)methyl)oxazol-5(4H)-one, Anti-oxidant, Anti-microbial activity, Nickel ferrite Bull. Chem. Soc. Ethiop. 2019, 33(3), 517-526.  DOI: https://dx.doi.org/10.4314/bcse.v33i3.1