Kinetic equation for hydrogen-induced direct phase transformations in Y2Fe17 magnetic alloy

Model for evolution of the hydrogen-induced direct phase transformation in Y2Fe17 magnetic alloy has been proposed. It is shown that evolution process of hydrogen-induced direct phase transformation in Y2Fe17 type hard magnetic alloy is controlled by diffusion process of Fe atoms in low temperatures interval of 330–750 oC. On the base of Kolmogorov and Lyubov kinetic theory has been obtained kinetic equation that well described the isothermal kinetic diagram for this type transformation in Y2Fe17 alloy.Предложена модель для развития индуцированного водородом прямого фазового превращения в магнитотвердом сплаве типа Y2Fe17. Показано что процесс развития индуцированного водородом прямого фазового превращения в магнитотвердом сплаве типа Y2Fe17 в низкотемпературном интервале 330–750 oC контролируется процессами диффузии атомов Fe. На основе кинетической теории фазовых превращений Колмогорова и Любова получено кинетическое уравнение, хорошо описывающее изотермическую кинетическую диаграмму для превращения такого типа в сплаве типа Y2Fe17

Isotope effects in high-Tc cuprate superconductors: Ultimate proof for bipolaron theory of superconductivity

Developing a theory of high-temperature superconductivity in copper oxides is one of the outstanding problems in physics. Twenty-five years after its discovery, no consensus on the microscopic theory has been reached despite tremendous theoretical and experimental efforts. Attempts to understand this problem are hindered by the subtle interplay among a few mechanisms and the presence of several nearly degenerate and competing phases in these systems. Here we provide unified parameter-free explanation of the observed oxygen-isotope effects on the critical temperature, the magnetic-field penetration depth, and on the normal-state pseudogap for underdoped cuprate superconductors within the framework of the bipolaron theory compatible with the strong Coulomb and Froehlich interactions, and with many other independent observations in these highly polarizable doped insulators. Remarkably, we also quantitatively explain measured critical temperatures and magnitudes of the magnetic-field penetration depth. The present work thus represents an ultimate proof of the bipolaron theory of high-temperature superconductivity, which takes into account essential Coulomb and electron-phonon interactions.Comment: 8 pages, 2 figure