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Magnetic memory cells associated with the stress-mediated magnetoelectric effect promise extremely low bit-writing energies. Most investigations have focused on the process of writing information in memory cells, and very few on readout schemes. The usual assumption is that the readout will be achieved using magnetoresistive structures such as Giant Magneto-Resistive stacks or Magnetic Tunnel Junctions. Since the writing energy is very low in the magnetoelectric systems, the readout energy using magnetoresistive approaches becomes non negligible. Incidentally, the magneto-electric interaction itself contains the potentiality of the readout of the information encoded in the magnetic subsystem. In this letter, the principle of magnetoelectric readout of the information by an electric field in a composite multiferroic heterostructure is considered theoretically and demonstrated experimentally using [N×(TbCo2/FeCo)]/[Pb(Mg1/3Nb2/3)O3](1−x)−[PbTiO3]x stress-mediated ME heterostructures.

We present here the demonstration of magnetoelectric switching of magnetization between two stable positions defined by a combination of anisotropy and magnetic field. A magnetoelastic nanostructured multilayer with the required uni-axial characteristic was deposited onto a commercial piezoelectric actuator. Thanks to the inverse magnetostrictive effect, the effective anisotropy of the magnetic element is controlled by the applied voltage and used to switch magnetization from one state to the other. Both vibrating sample magnetometer and magneto-optical Kerr effect measurements have been performed and demonstrate the magnetoelectric switching.

We present here the implementation of a magnetoelectric memory with a voltage driven writing method using a ferroelectric relaxor substrate. The memory point consists of a magnetoelastic element in which two orthogonal stable magnetic states are defined by combining uni-axial anisotropy together with a magnetic polarization in the hard axis direction. Using a ferroelectric relaxor substrate, an anisotropic stress is created in the magnetic element when applying a voltage across electrodes. Because of the inverse magnetostrictive effect, the effective anisotropy of the magnetic element is controlled by the applied voltage and used to switch magnetization from one state to the other.

Polarization of electromagnetic waves plays an extremely important role in interaction of radiation with matter. In particular, interaction of polarized waves with ordered matter strongly depends on orientation and symmetry of vibrations of chemical bonds in crystals. In quantum technologies, the polarization of photons is considered as a “degree of freedom”, which is one of the main parameters that ensure efficient quantum computing. However, even for visible light, polarization control is in most cases separated from light emission. In this paper, we report on a new type of polarization control, implemented directly in a spintronic terahertz emitter. The principle of control, realized by a weak magnetic field at room temperature, is based on a spin-reorientation transition (SRT) in an intermetallic heterostructure TbCo2/FeCo with uniaxial in-plane magnetic anisotropy. SRT is implemented under magnetic field of variable strength but of a fixed direction, orthogonal to the easy magnetization axis. Variation of the magnetic field strength in the angular (canted) phase of the SRT causes magnetization rotation without changing its magnitude. The charge current excited by the spin-to-charge conversion is orthogonal to the magnetization. As a result, THz polarization rotates synchronously with magnetization when magnetic field strength changes. Importantly, the radiation intensity does not change in this case. Control of polarization by SRT is applicable regardless of the spintronic mechanism of the THz emission, provided that the polarization direction is determined by the magnetic moment orientation. The results obtained open the prospect for the development of the SRT approach for THz emission control.

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We investigated the terahertz (THz)-frequency resonances of two-dimensional electron conductivity under the streaming transport in a GaN quantum well at the nitrogen temperature. The calculation results found that the negative microwave mobility can occur in the narrow windows near the optical-phonon transit-time resonance frequencies, which can be tuned electrically in the 0.2–2.5THz range with the static electric fields of 1–10kV∕cm. The estimated magnitude of the negative mobility reaches hundreds of cm2∕Vs. These effects suggest that the nitride-based heterostructure may enable the development of an electrically pumped, tunable THz source operating at or above 77K.