A new spintronic theory has been developed for the magnetic tunnel junction (MTJ) with single-crystal barrier. The barrier will be treated as a diffraction grating with intralayer periodicity, the diffracted waves of tunneling electrons thus contain strong coherence, both in charge and especially in spin. The theory can answer the two basic problems present in MgO-based MTJs: (1) Why does the tunneling magnetoresistance (TMR) oscillate with the barrier thickness? (2) Why is the TMR still far away from infinity when the two electrodes are both half-metallic? Other principal features of TMR can also be explained and reproduced by the present work. It also provides possible ways to modulate the oscillation of TMR, and to enhance TMR so that it can tend to infinity. Within the theory, the barrier, as a periodic diffraction grating, can get rid of the confinement in width, it can vary from nanoscale to microscale. Based on those results, a future-generation MTJ is proposed where the three pieces can be fabricated separately and then assembled together, it is especially appropriate for the layered materials, e.g., MoS2 and graphite, and most feasible for industries.

The upgrade of the LHC to the High-Luminosity LHC (HL-LHC) is expected to increase the LHC design luminosity by an order of magnitude. This will require silicon tracking detectors with a significantly higher radiation hardness. The CMS Tracker Collaboration has conducted an irradiation and measurement campaign to identify suitable silicon sensor materials and strip designs for the future outer tracker at the CMS experiment. Based on these results, the collaboration has chosen to use n-in-p type silicon sensors and focus further investigations on the optimization of that sensor type. This paper describes the main measurement results and conclusions that motivated this decision.

We have developed a tunneling theory to describe the temperature dependence of tunneling magnetoresistance (TMR) of the magnetic tunnel junctions (MTJs) with periodic grating barrier.Through the Patterson function approach, the theory can handle easily the influence of the lattice distortion of the barrier on the tunneling process of the electrons. The lattice distortion of the barrier is sensible to the temperature and can be quite easily weakened by the thermal relaxation of the strain, and thus the tunneling process of the electrons gets changed highly with the variation of the temperature of the system. That is just the physical mechanism for the temperature dependence of the TMR. From it, we find that the decrease of TMR with rising temperature is mostly carried by a change in the antiparallel resistance (R AP ), and the parallel resistance (R P ) changes so little that it seems roughly constant, if compared to the R AP , and that, for the annealed MTJ, the R AP is significantly more sensitive to the strain than the R P , and for non-annealed MTJ, both the R P and R AP are not sensitive to the strain. They are both in agreement with the experiments of the MgO-based MTJs. Other relevant properties are also discussed.

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We have developed a spintronic theory for magnetic tunnel junctions consisting of a single-crystal barrier and two half-metallic ferromagnetic electrodes. Radically different from the conventional theories, the barrier is now regarded as an optical diffraction grating, and treated by the traditional optical scattering method, i.e. Bethe theory and two-beam approximation. After tunneling, the electrons can thus possess high coherence. In the case that the electrodes are both half-metallic, the conventional theories give an infinite tunneling magnetoresistance (TMR). By contrast, in the Bethe theory and two-beam approximation, there can exist the scattering channels of nonconservation of energy. Therefore, the TMR can still be far away from infinity, which is in accordance with experiments. Also, we find that, due to the half-metallicity of the electrodes, the parallel conductance oscillates with temperature whereas the antiparallel conductance will increase other than oscillate with temperature. That is in agreement with experiments, too. Finally, two applications of the present theory are discussed with regard to the material design and engineering: one is how to choose appropriate materials for the barrier to realize infinite TMR; the other is a criterion for judging whether a material is half-metallic or not.