This review provides a theoretical basis for understanding the current-phase relation (C⌽R) for the stationary (dc) Josephson effect in various types of superconducting junctions. The authors summarize recent theoretical developments with an emphasis on the fundamental physical mechanisms of the deviations of the C⌽R from the standard sinusoidal form. A new experimental tool for measuring the C⌽R is described and its practical applications are discussed. The method allows one to measure the electrical currents in Josephson junctions with a small coupling energy as compared to the thermal energy. A number of examples illustrate the importance of the C⌽R measurements for both fundamental physics and applications.

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We study the critical temperature T_c of SFF trilayers (S is a singlet superconductor, F is a ferromagnetic metal), where the long-range triplet superconducting component is generated at noncollinear magnetizations of the F layers. We demonstrate that T_c can be a nonmonotonic function of the angle \alpha between the magnetizations of the two F layers. The minimum is achieved at an intermediate \alpha, lying between the parallel (P, \alpha=0) and antiparallel (AP, \alpha=\pi) cases. This implies a possibility of a "triplet" spin-valve effect: at temperatures above the minimum T_c^{Tr} but below T_c^{P} and T_c^{AP}, the system is superconducting only in the vicinity of the collinear orientations. At certain parameters, we predict a reentrant T_c(\alpha) behavior. At the same time, considering only the P and AP orientations, we find that both the "standard" (T_c^{P} < T_c^{AP}) and "inverse" (T_c^{P} > T_c^{AP}) switching effects are possible depending on parameters of the system.Comment: 5 pages (including 4 EPS figures

Quantitative theory of the Josephson effect in SFIFS junctions (S denotes bulk superconductor, F - metallic ferromagnet, I - insulating barrier) is presented in the dirty limit. Fully self-consistent numerical procedure is employed to solve the Usadel equations at arbitrary values of the F-layers thicknesses, magnetizations, and interface parameters. In the case of antiparallel ferromagnets' magnetizations the effect of the critical current enhancement by the exchange field is observed, while in the case of parallel magnetizations the junction exhibits the transition to the pi-state. In the limit of thin F layers, we study these peculiarities of the critical current analytically and explain them qualitatively; the scenario of the 0-pi transition in our case differs from those studied before. The effect of switching between 0 and pi states by changing the F-layers' mutual orientation is demonstrated.Comment: 5 pages, 4 EPS figures; the style file jetpl.cls is included. Version 2: minor correction