Weiping Zhou

Electric field manipulation of nonvolatile magnetization in Au/NiO/Pt heterostructure with resistive switching effect

The electrical field manipulation of magnetization is investigated in an Au/NiO/Pt heterostructure, which is fully compatible with the standard complementary metal-oxide semiconductor process. Reversible and stable unipolar resistive switching effects as well as a significant nonvolatile change of the magnetization are observed in this device during the set and reset processes at room temperature. Further analysis indicates that the formation and rupture of metallic Ni conducting filaments caused by the electric field would be responsible for the changes of resistivity and magnetization. The coexistence of the electric field control of magnetization change and resistive switching makes Au/NiO/Pt heterostructure a promising candidate for the multifunctional memory devices.

Multilevel Resistance Switching Memory in La2/3Ba1/3MnO3/0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (011) Heterostructure by Combined Straintronics-Spintronics

We demonstrate a memory device with multifield switchable multilevel states at room temperature based on the integration of straintronics and spintronics in a La2/3Ba1/3MnO3/0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) (011) heterostructure. By precisely controlling the electric field applied on the PMN-PT substrate, multiple nonvolatile resistance states can be generated in La2/3Ba1/3MnO3 films, which can be ascribed to the strain-modulated metal-insulator transition and phase separation of Manganite. Furthermore, because of the strong coupling between spin and charge degrees of freedom, the resistance of the La2/3Ba1/3MnO3 film can be readily modulated by magnetic field over a broad temperature range. Therefore, by combining electroresistance and magnetoresistance effects, multilevel resistance states with excellent retention and endurance properties can be achieved at room temperature with the coactions of electric and magnetic fields. The incorporation of ferroelastic strain and magnetic and resistive properties in memory cells suggests a promising approach for multistate, high-density, and low-power consumption electronic memory devices.

Manipulation of anisotropic magnetoresistance and domain configuration in Co/PMN-PT (011) multiferroic heterostructures by electric field

The electric field manipulation of magnetic anisotropy and domain configuration has been investigated in the artificial multiferroic Co/PMN-PT (011) heterostructure at room temperature. A uniaxial magnetic anisotropy is induced with the application of an electric field, which leads to an electrically switched anisotropic magnetoresistance with tunability as large as ∼29%. Furthermore, the magnetic domain structures of Co films are investigated by magnetic force microscopy under an in situ electric field, which exhibits direct evidence for electric field control of magnetism at the mesoscale. The converse magnetoelectric effect demonstrated in this multiferroic heterostructure has potential to be utilized in magnetoelectric devices with low power consumption.

The influence of Nd3+ ions doping on structural, dielectric and magnetic properties of Ni–Zn ferrites

The impact of neodymium substitution on structural, dielectric and magnetic properties of polycrystalline Ni0.5Zn0.5NdxFe2−xO4 (0.002 ≤ x ≤ 0.010) ferrites have been investigated. XRD results demonstrate that all the samples crystallize in single-phase cubic spinel structure except with x = 0.010. The substitution of neodymium monotonously expands the lattice parameter. The compositional variation of dielectric constant and dielectric loss tangent is abnormal, displaying a peak at x = 0.008. Typical soft ferromagnetic characteristics of M-H curves are observed at room temperature and the saturation magnetization decreases linearly with increasing Nd3+ content. The mechanism of doping induced modulation on structural, dielectric and magnetic properties is discussed.

Visualization of deep ultraviolet photons based on Förster resonance energy transfer and cascade photon reabsorption in diphenylalanine-carbon nitrides composite film

A diphenylalanine (L-Phe-L-Phe, FF)-carbon nitride composite film is designed and fabricated to visualize the deep ultraviolet (DUV, 245–290 nm) photons. The FF film, composed of diphenylalanine molecules, doped with carbon nitrides shows blue emission under excitation of DUV light, which makes the DUV beam observable. Both Forster resonance energy transfer and cascade photon reabsorption contribute to the conversion of photon energy. First, the FF is excited by the DUV photons. On one hand, the energy transfers to the embedded carbon nitrides through nonradiative dipole–dipole couplings. On the other hand, the 284 nm photons emitted from the FF would further excite the carbon nitrides, which will finally convert to blue fluorescence. Herein, the experimental demonstration of a simple device for the visualization of high DUV fluxes is reported.

Point defects and magnetic properties of neutron irradiated MgO single crystal

(100)-oriented MgO single crystals were irradiated to introduce point defects with different neutron doses ranging from 1.0×1016 to 1.0×1020 cm-2. The point defect configurations were studied with X-ray diffuse scattering and UV-Vis absorption spectra. The isointensity profiles of X-ray diffuse scattering caused by the cubic and double-force point defects in MgO were theoretically calculated based on the Huang scattering theory. The magnetic properties at different temperature were measured with superconducting quantum interference device (SQUID). The reciprocal space mappings (RSMs) of irradiated MgO revealed notable diffuse scattering. The UV-Vis spectra indicated the presence of O Frenkel defects in irradiated MgO. Neutron-irradiated MgO was diamagnetic at room temperature and became ferromagnetic at low temperature due to O Frenkel defects induced by neutron-irradiation.