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Spin Filter Tunneling
Published in Evgeny Y. Tsymbal, Žutić Igor, Spintronics Handbook: Spin Transport and Magnetism, Second Edition, 2019
Tiffany S. Santos, Jagadeesh S. Moodera
Transport experiments of EuS and EuSe films by Esaki et al. [26], performed previous to the field-emission experiments, showed indirect evidence of the spin filter effect. The EuS and EuSe films in this study were 20 and 60 nm thick, between either Al or Au electrodes. With this trilayer structure, they observed tunneling across the potential barrier between the metal and the EuX layer, as shown in Figure 14.3a. This potential barrier was formed by the energy difference between the Fermi level of the metal electrode and the bottom of the conduction band in the EuX. When measuring the temperature dependence of the I–V behavior of these structures, a significant drop in voltage (measured with constant current) occurred below the TC for both EuS and EuSe junctions, shown in Figure 14.3b. This drop resulted from the exchange splitting of the conduction band, thereby lowering the barrier height. Applying a magnetic field shifted the drop to a temperature slightly higher than the TC. However, the 20% decrease in voltage below ~10 K in zero field for EuSe is surprising given that it is an antiferromagnet at zero field and thus no exchange splitting was expected (see below the discussion for EuSe). Spin polarization of the current was not quantified in this early experiment, whereas it showed indirect evidence of the spin filter effect. Similar behavior of tunnel junction resistance can be seen for all Eu chalcogenide junctions described later. A few years after Esaki’s work, Thompson et al. [27] also measured an increase in conductance at low temperature due to conduction band splitting in a Schottky barrier contact between a EuS single crystal and indium metal.
Superconducting Devices
Published in R. D. Parks, Superconductivity, 2018
Double junction coherence effects were reported by Jaklevic et al. (105) using evaporated film junctions. They were able to exploit the phenomenon for flux measurement, using a junction loop area of 7 × 10−4 cm2, which had an applied field periodicity of ϕ0/7 × 10−4 = 3 × 10−4 G. The effect has been used in a superconducting ammeter by Clarke (106) using the structure shown in Fig. 38 and named SLUG (Superconducting Low Inductance Undulating Galvanometer). This consisted of a Sn–Pb solder bead formed on a niobium wire, and behaved like a Josephson junction pair when subjected to magnetic fields produced by passing current through the wire. The structure behaved as though Josephson tunneling took place at the edges of the bead, and as though the loop area consisted of the penetration depth regions in the solder and Nb which are shown dashed in the figure. For increased sensitivity Clarke used an insulated Nb wire with the solder bead formed over a region in which a narrow slot had been scraped through the insulation along the wire. This had the result of concentrating the wire current in the slot region,‡ thus increasing the junction field per unit modulating current. This device exhibited a modulation current period of 200 μA. By use of a special circuit to monitor the critical current, the modulation current could be controlled to within 12% so that the device could detect current changes of 1 μA. With an effective input inductance of 10−8 H, it could sense 5 × 10−14 V with a time constant of 15 sec.
Potentiometry: pH and Ion-Selective Electrodes
Published in Grinberg Nelu, Rodriguez Sonia, Ewing’s Analytical Instrumentation Handbook, Fourth Edition, 2019
Ronita L. Marple, William R. LaCourse
A double junction reference electrode has two junctions. The first junction separates the reference electrode from an intermediate solution, and the second isolates the intermediate solution from the test solution. This reference electrode can be used to minimize contamination of the test solution.
Examining the factors effecting severity of two-wheeler crashes at intersections
Published in International Journal of Crashworthiness, 2022
Ankit Choudhary, Rahul Dev Garg, Sukhvir Singh Jain
The types of junctions consisted of three categories, 4-leged junction, T- junction and Y-junction. The junction control measures were divided into four categories, i.e. traffic signals, stop-sign or sign-boards, un-controlled and others [51]. Others include the speed breakers and barricading near junctions.