Electrical spin injection into semiconductors [1] is a pre-requisite for semiconductor spintronics, where the spin (in addition to the charge) of the carriers would carry information. A possible way to perform an efficient electrical spin injection is to use ferromagnetic metals (Co, CoFeB…) as spin injectors, and to cross the metal/semiconductor interface through a tunnel barrier (MgO, SiO2…). Among the possible systems, spin optoelectronic devices (spin light-emitting diodes [1], spin lasers and spin photodiodes), where the carrier spin can be converted into photon helicity (and vice-versa), have gained intensive interest in the last decade. The potential applications are optical free-space communication, 3D displays, biomedical analyses…. However, according to the optical selection rules for surface emitting devices, it is usually necessary to apply a strong external magnetic field in the range of a few Teslas on the conventional magnetic electrodes with in-plane magnetization in order to rotate it out-of-plane and inject spins oriented perpendicularly to the interface. A magnetic field of the same amplitude is also necessary to switch the magnetization and thus the light helicity.Using such large magnetic field is impossible for the practical applications. In this talk, progress on SpinLEDs based on Perpendicular Magnetic Anisotropy (PMA) CoFeB/MgO spin injectors will be presented, where spin injection occurs without the need of any external magnetic field. In particular, electrical spin injection into a single InAs/GaAs quantum dot will be evidenced at zero magnetic field [2], as well as electrical initialization of nuclear spins in the dot. Finally, we will present very recent advances concerning the switching of the magnetic electrode, that can be performed by electrical means. The switching relies on the Spin Transfer Torque (STT) effect using an auxiliary spin current generated by charge/spin conversion(by Spin Hall Effect SHE) of a lateral auxiliary charge current propagating in the Ta/CoFeB electrode. Large circular polarization of the light (>30%) emitted by the spinLED, and robust electrical switching of the photon helicity have been demonstrated at room temperature [3].

[1] R. Fiederling et al., Nature 402, 787 (1999)

[2] F. Cadiz et al., Nanolett. 18, 2381 (2018)

[3] Y. Lu et al., March Meeting, Las Vegas (2023)

This project receives funding in the European Commission’s Horizon 2020 Research Programme under Grant Agreement Number 818087.

The operation of a lithium-ion battery (LIB) cell is governed by the much desirable periodicity and reversibility of lithium ions extraction and insertion mechanisms, as they are transported between the electrodes, keeping the capacity retention high. Unavoidably, there is an irreversible part manifested as capacity loss due to solid electrolyte interphase (SllEI) growth, contact loss, active material deterioration and lithium inventory loss, factors that are extensively documented and studied, mainly through the electric parameters of current, voltage and charge from cell level to commercial operating battery packs. Only recently the interest towards probing the mechanical behavior has grown and the criticality of such information, in understanding the inner workings of secondary battery cells, has been appreciated. Parameters such as the mechanical stress, volume expansion and pressure are gaining ground in State of Charge (SoC) and State of Health (SoH) monitoring. From the comparison of stored charge, incremental capacity peak intensity and position and state of health against pressure it was revealed that there is a strong connection between pressure and peak intensity.