Focus on hybrid magnetic/superconducting systems

Abstract

Like antagonistic cousins from a common heritage, the competition between superconductivity and magnetism for correlated electron states, and coexistence in some rare cases, produces a rich variety of physical behavior, useful materials, and technologically important properties. Many pages of Superconductor Science and Technology are devoted to cuprates, pnictides, and other compounds where the mechanism of superconductivity itself is intertwined with magnetism. This focus issue explores another area, in which superconductivity and magnetism are combined as a hybrid system to create new properties not possible with either system alone, or to improve upon the properties of either system in dramatic ways.In recent years, great progress has been made in this exciting, relatively new field, followed by many workshops and special sessions in major international conferences. A concise and up-to-date focus issue of Superconductor Science and Technology is timely to summarize the latest developments. We, the Guest Editors, would like to thank those colleagues who contributed their most recent and interesting findings to this focus issue: Silhanek and co-workers reported both theoretical and experimental investigations of the dynamics of vortex chains for different arrangements of magnetic moments. Their approach of time-dependent Ginzburg–Landau formalism now replaces the previously proposed empirical models to explain the most relevant properties of the dynamics of these S/F hybrid systems. Hikino and co-workers presented a new route to observe the spin-wave excitation by the Josephson effect, through a theoretical investigation of the resistively shunted junction model, extended by considering the gauge invariance including magnetization. When the magnetization is driven by the microwave adjusted to the ferromagnetic resonance frequency, the dc supercurrent is induced in the junction, and the current-voltage curve shows step structures as a function of applied voltage. The magnitudes of step-height can be controlled by tuning the shape of interface. Nevirkovets and Belogolovskii demonstrated theoretically and experimentally that an ultra thin ferromagnetic layer, nearly transparent for non-superconducting charge transport, can block the transport of charge-carrier superconducting correlations as a cut-off filter in some device applications, for instance, a few nanometer thick ferromagnetic layer in a double barrier S1IS2FIS3 multi-terminal devices (S, I, and F are superconductor, insulator, and ferromagnetic metal, respectively) considerably improves the device's input-output isolation in comparison with the symmetric S1IS2IS3 devices. These are just a few examples among many exciting works published in this focus issue.Last but not the least, we owe many thanks to Tom Miller, the publisher of Superconductor Science and Technology, who not only agreed to publish this focus issue, but also was an inspirational driver that made the Guest Editors' work a lot easier and rewarding.