Layered ferromagnet-superconductor structures: the π\pi state and proximity effects

We investigate clean mutilayered structures of the SFS and SFSFS type, (where the S layer is intrinsically superconducting and the F layer is ferromagnetic) through numerical solution of the self-consistent Bogoliubov-de Gennes equations for these systems. We obtain results for the pair amplitude, the local density of states, and the local magnetic moment. We find that as a function of the thickness $d_F$ of the magnetic layers separating adjacent superconductors, the ground state energy varies periodically between two stable states. The first state is an ordinary "0-state", in which the order parameter has a phase difference of zero between consecutive S layers, and the second is a "$\pi$-state", where the sign alternates, corresponding to a phase difference of $\pi$ between adjacent S layers. This behavior can be understood from simple arguments. The density of states and the local magnetic moment reflect also this periodicity.Comment: 12 pages, 10 Figure

[Features of pathological changes in patients with different types of pancreatic pseudocyst]

Background. A growing number of patients with pancreatic pseudocyst on the background of acute or chronic pancreatitis or due to injury of the pancreas encourages scientists to study the etiology and pathogenesis of this disease. Objective. Тo study morphological features of various types of wall structure and adjacent parenchyma of pseudocyst using histochemical techniques. Methods. Resected pancreatic specimens taken intraoperative from 47 patients were used as a material. Results. Patients of the first group with forming acute pseudocyst on the background of acute destructive pancreatitis, characterized by severe circulatory disorders in pancreas, destructive changes of all structural components of the gland with subsequent development of reactive inflammatory response to injury in the form of diffuse or focal leukocyte infiltration of the stroma and the parenchyma and signs of original reparative process. In all patients of the second group with postnecrotic chronic pseudocyst the wall of pseudocyst was represented by granulation tissue and fibrous layer. In the surrounding pancreatic tissues it was revealed morphological signs of chronic pancreatitis with fibrotic stromal changes and chronic inflammatory infiltration, parenchymal atrophy and restructuring of false acinar lobules, metaplasia of their cell. All patients of the third group demonstrated a pronounced fibrosis of the stroma with atrophy of parenchyma and restructuring of all components of the pancreas: the formation of false acinar lobules, compensatory hypertrophy of islet apparatus,restructuring of ductal system of pancreas, formation of retention pseudocyst with a fibrous wall lined with epithelium with signs of hyperplasia and metaplasia. Conclusion. Morphological changes that occur during formation of pseudocyst lead to organ dysfunction and should be considered as an adverse pathological process that requires surgical correction. Citation: Krivoruchko IA, Goncharova NМ, Sorokina IV. [Features of pathological changes in patients with different types of pancreatic pseudocyst]. Morphologia. 2015;9(3):31-41. Ukrainian

Surface segregation and charge state of La₀.₇Sr₀.₃MnO₃

Nuclear magnetic resonance and secondary ion mass-spectroscopy have been used to study the surface charge and surface chemical compositions of La₀.₇Sr₀.₃MnO₃ nanoparticles of 12 and 50-100 nm size. It is found that the surface of particles is characterized by an increased content of Sr and Mn ions than the bulk, while the difference depends on particle size. The surface segregation process is considered to be a possible mechanism for cation rearrangement. Thus, the observed magnetically dead layer on a particle surface may be formed due to increase in the Sr and Mn ions concentrations up to values corresponding to an antiferromagnetic state.Методами ядерного магнитного резонанса и вторичной ионной масс-спектроскопии проведены исследования зарядового состояния и химического состава поверхности наночастиц La₀.₇Sr₀.₃MnO₃ с размерами 12 и 50-100 нм. Обнаружено, что для поверхности частиц характерно повышенное содержание ионов Sr и Mn по сравнению с объемом, причем это различие зависит от размера частиц. В качестве возможного механизма перераспределения катионов рассматривается процесс поверхностной сегрегации. Таким образом, наблюдаемый немагнитный слой па поверхности частиц может быть сформирован в результате увеличения концентрации ионов Sr и Mn в поверхностном слое до величин, соответствующих антиферромагнитному состоянию.Методами ядерного магнітного резонансу і вторинної іонної мас-спектроскопії проведено дослідження зарядового етапу та хімічного складу поверхні наночастинок La₀.₇Sr₀.₃MnO₃ з розмірами 12 і 50-100 нм. Виявлено, що для поверхні частинок характерний підвищений склад іонів Sr і Mn, а їхня концентрація залежить від розміру частинок. Як можливий механізм перерозподілу катіонів розглядається процес поверхневої сегрегації. Таким чином, немагнітний шар, що спостерігається на поверхні частинок, може бути сформований в результаті збільшення концентрації іонів Sr і Mn у поверхневому шарі до величин, що відповідають антиферомагнітному етапу

Peculiarities of electromagnetic waves absorption in polymer magnetic nanocomposites (La,Sr)MnO₃

The results of research of the nonresonant and magnetic resonance absorption of electromagnetic waves in polymer magnetic nanocomposites (La₀.₇Sr₀.₃Mn₀.₃) in 10-40 GHz and 60-78 GHz frequency bands are presented. The absorption magnitude up to -7.5 dB at 32-35 GHz has been detected for the composite with 60 % filling and a layer thickness of 0.53 mm. The analysis of results obtained proves a high level homogeneity of magnetic nanoparticles distribution in the polymer matrix. The most probable reasons of unusually large value of the spectroscopic splitting factor, obtained by Electron Spin Resonance technique, are under discussion. The results of design of the technology and the manufacturing technique of ferromagnetic composites together with epoxy-polysiloxane polymer matrix are presented