Josephson effect device

Low-magnetic-field applications. These applications include Josephson-effect devices, magnetic-flux shields, transmission fines, and resonant cavities, all of which require superconducting materials having a high critical temperature and a high critical magnetic field. 

Superconducting electronic devices are in a different class. They rely on two phenomena the Josephson effect and the quantisation of magnetic flux, which are described in a simple way in ref. [46], while a more complete account is given in ref. [47],... 

In 1962 a postgraduate student, Brian Josephson, working in the University of Cambridge, and later to win a Nobel Prize, predicted that Cooper pairs should be able to tunnel through a thin (approximately 1 nm) insulating barrier from one superconductor to another with no electrical resistance [46]. This quantum tunnelling was confirmed by experiment and is known as the Josephson effect . The superconducting electronic devices exploit Josephson junctions. 

In 1962, B. D. Josephson predicted that Cooper pairs in superconductors could tunnel through an insulating barrier without encountering electrical resistance, the Josephson effect. A Josephson junction allows current to flow with no resistance with no apphed field. However, at a critical voltage level, the Cooper pairs split up and normal quantum-mechanical tunneling occurs with resistive losses. The Josephson effect allows the fabrication of microelectronic switches and transistors that operate faster and with lower power loss than semiconductor devices. 

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The current status of investigations of spin valve effects in structures composed of superconducting and ferromagnet layers is briefly reviewed. The main difficulties on the way of realization of SF spin valve devices are outlined. It is demonstrated that some of them can be effectively overcome by the use of trilayer femomagnetic - normal metal -ferromagnet structures as a weak link of Josephson junctions. 

Thus, we can conclude that in order to fabricate practical Josephson spin valve devices one should solve at least two problems. The first is to find a way for increasing the scale of the decay lengths 2- The second is to propose a structure providing effective exchange of electrons between F layers. 

In conclusions, we believe that a use of FNF multilayer as a building block of SF spin valves opens an opportunity for effective control of magnitude and sign of Josephson junction critical current. Utilization of FNF multilayers also opens a way to engineering non Josephson spin valve devices. 

An important potential use is in logic components in high-speed computers. Josephson Junctions can switch states very quickly (as low as 6 picoseconds). Moreover they have very low power consumption and can be packed closely without generating too much heat. It is possible that computers based on such devices could operate 50 times faster than the best existing machines. The effects are named after Brian Josephson (1940- ), who predicted them theoretically in 1962. 

Superconductors exhibit a number of properties such as zero resistance, the Meissner effect, Josephson tunneling, the proximity effect, and persistent currents (12 ) that make them well suited for use in electronic devices and sensors. Accordingly, superconducting electronic devices are particularly attractive due to the ultra-low power dissipation and ultra-fast response times that can be achieved from such substances (13). 

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