The structures and magnetic properties of Cr/Fe and Mn/Fe thin films

Cr_1-x Fe _x and Mn_1-x Fe _x films were prepared at room temperature by thermal coevaporation at a deposition rate of about 25 Å/min. It was found that an amorphous phase can be obtained for Cr_1-x Fe _x (0.25<x<0.60) films, while a metastable-Mn-type phase was observed for Mn_1-x Fe _x (x<0.70) films. The influence of the structure on the magnetic properties has been studied. The amorphization ability of the two systems was discussed in terms of thermodynamic considerations.     

Synthesis,structure, characterization and biological evaluation of 3‐substituted 1‐pyridin‐2‐ylimidazo[1,5‐a]pyridine‐based copper(I)–phosphine complexes for anticancer drug screening

Copper(I) complexes of the types [Cu(N–N)(PPh₃)₂]NO₃ (LC41–LC44) and [Cu(N–N)(PPh₃)(NO₃)] (LC45) carrying 3‐substituted 1‐pyridine‐2‐ylimidazo[1,5‐a]pyridine (N–N) derivatives and triphenylphosphine (PPh₃) ligands have been prepared. The synthesized copper(I)–phosphine complexes were fully characterized by NMR, IR, ESI‐MS and UV–visible spectroscopy as well as by cyclic voltammetry. Selected structures such as LC42, LC43 and LC45 were additionally analysed by single‐crystal X‐ray method, which show that copper(I) centre adopts a highly distorted tetrahedral geometry. The ¹H and ¹³C NMR spectral data of the complexes throw light on the nature of metal–ligand bonding. They display dπ–π* metal‐to‐ligand charge transfer (MLCT) transition and show quasireversible Cu^I/Cu^II metal oxidation. Among the copper(I)–phosphine complexes, LC41–LC44 exhibit moderate cytotoxicity (IC₅₀: 24 h, 67–74 μM; 48 h, 58–70 μM) against human lung epithelial adenocarcinoma A549 cells, whereas LC45 displays the best activity (IC₅₀: 24 h, 42 μM; 48 h, 34 μM) for A549 cancer cell line, which is better than that of the commercial antitumor drug cisplatin. All the complexes also displayed excellent selectivity by being relatively inactive against the human lung epithelial L132 normal cell line with selectivity index (SI) values ranging from 3.4 to 7.4. The complexes block cell cycle progression of A549 cells in G₀/G₁ phase. FACSVerse analyses are suggestive of reactive oxygen species (ROS) generation and apoptotic cell death induced by the LC41, LC43 and LC45. The induction of apoptosis in A549 cells was shown by Annexin V with propidium iodide (PI) and 4′,6‐diamidino‐2‐phenylindole (DAPI) staining methods and established the ability of LC41, LC43 and LC45 to accumulate in the cell nuclei.     

Pb1−x Fe x films prepared by vapor condensation

ZF, LF and TF SR experiments with antiferromagnetic (AF) ceramical samples La_2–x Sr _x CuO_4–y have been performed in the temperature range 10–300 K. Zero field muon spin polarization functions obtained below the Neel temperature clearly show a nonzero initial precession phase-–0.35 rad. We propose an explanation based on existence of the dynamical magnetic fields on the muon.We thank Drs. A.G. Chistov and A.M. Brjazkalo from RSC Kurchatov Institute for the preparation the #2 La₂CuO_4–y sample.     

Mössbauer study of aging and annealing effects of Ag50Fe50 film

Aging at room temperature (RT) and thermal annealing of Ag₅₀Fe₅₀ films prepared by coevaporation method have been studied by in situ Mössbauer spectroscopy. Coherently precipitated fcc-Fe due to the segregation of Fe has been observed after aging and annealing at temperatures below 157°C, and α-Fe precipitation occurs at higher annealing temperatures.     

In situ Mössbauer studies of vapor quenched Ag/Fe and Au/Fe films

Metastable alloys of Ag_1-xFe_x (x=0.17, 0.30, 0.50, 0.54, 0.56 and 1.0) and the stable Au_1-yFe_y (y=0.18 and 0.25) alloy were prepared as thin films by vapor quenching method on low temperature kapton substrate. The X-ray diffraction spectra of all Ag/Fe samples. withx<-0.56, have indication of fee structure with very small grain size. The present work reports in-situ Mössbauer results on Ag/Fe and Au/Fe films. The spectra obtained are characteristic of homogeneous disordered alloy with broad magnetic hyperfine field distribution. Aging effect inducing cluster formation was observed in Ag/Fe films after they were heated to room temperature, but this behavior was not detected in Au/Fe samples.     

Preparation and Mössbauer studies of iron-mercury mixed isocyanide-carbonyl complexes

The reactions of [Fe(t-BuNC)3(CO)2] with HgX2 (X= Cl, Br or I) give two different types of iron-mercury halide complex, depending on the molar ratio of reactants used. An equimolar ratio of the reactants produces the neutral adducts [Fe(t- BuNC)3(CO)2(HgX2)],whereas two equivalents of HgX2 generate the electrolytes [Fe(t- BuNC)3(CO)2(HgX)]HgX3. The Mössbauer, i.r. data, and conductivity measurements of these complexes are presented and discussed in terms of their chemical structures and bonding.     

Mechanical alloying of Fe and Cr: Structural and magnetic studies

Mechanical milling of a mixture of pure iron and chromium powders with a nominal composition of 28 at. % of Fe and 72 at. % of Cr was performed using two kinds of tools. The alloying process was followed by X ray diffraction and⁵⁷Fe Mössbauer spectroscopy. The room temperature Mössbauer spectra revealed the formation of a broad single line at the expense of the area of α-Fe sextet. At 4.2 °K most of the singlet still remains unsplit. This behavior may be due to some metastable structure induced by the preparation method.     

Comparison of ball milling of Fe/Cr powders and Fe-Cr crystalline alloy

Using the mechanical attrition technique (MA), we have prepared a Fe-Cr alloy starting with a mixture of elemental iron and chromium powders with a nominal composition of 28 at% of Fe and 72 at% of Cr. MA was also performed on solid solutions of Fe₂₈Cr₇₂ crystalline alloy. The Mössbauer effect of the mechanically alloyed powder from Cr and Fe metals has been compared with that from crystalline alloy.     

Exchange bias and anomalous vertical shift of the hysteresis loops in milled Fe/MnO2 material

The present article reports studies on structural and magnetic properties of nanostructured Fe/MnO₂ materials prepared by mechanosynthesis method, with Fe to MnO₂ ratios of 20/80, 50/50 and 60/40. X-ray diffraction patterns indicate that the milled materials have crystalline grain size in the nanoscale region. Mössbauer spectra of the milled materials suggest the presence of two Fe phases for each sample: a nanocrystalline α$\mathrm{\alpha }$-Fe phase with a high degree of disorder/defects and small Fe-oxide particles. The magnetic hysteresis (M(H)$M(H)$) loops, measured at 4.2 K, after the samples were cooled from 300 K in ±10 kOe fields, show unexpected large shifts in both horizontal and vertical directions for the 20/80 sample, while only horizontal shift was detected in the samples with higher Fe concentration. The anomalous vertical shift of the M(H)$M(H)$ loop for the 20/80 sample, observed at low cooling field (10 kOe), is being associated with a large contribution from non-collinear magnetic structure of the particles surface. This surface magnetic contribution is strongly influenced by the field cooling magnitude. A simple model is proposed to interpret this result.