Yongchao Li

The toxicity of cadmium to three aquatic organisms (Photobacterium phosphoreum, Daphnia magna and Carassius auratus) under different pH levels

This study investigated the effect of pH on cadmium toxicity to three aquatic organisms: Photobacterium phosphoreum, Daphnia magna and Carassius auratus. The acute toxicity of Cd(2+) to P. phosphoreum and D. magna at five pH values (5.0, 6.0, 7.0, 8.0, and 9.0) was assessed by calculating EC50 values. We determined that Cd(2+) was least toxic under acidic conditions, and D. magna was more sensitive to the toxicity of Cd than P. phosphoreum. To evaluate Cd(2+)-induced hepatic oxidative stress in C. auratus at three pH levels (5.0, 7.25, 9.0), the activity of antioxidant enzymes (superoxide dismutase, catalase and glutathione peroxidase), the level of glutathione and the malondialdehyde content in the liver were measured. Oxidative damage was observed after 7d Cd exposure at pH 9.0. An important finding of the current research was that Cd(2+) was generally more toxic to the three test organisms in alkaline environments than in acidic environments.

Electric field control of magnetism without magnetic bias field in the Ni/Pb(Mg1/3Nb2/3)O3-PbTiO3/Ni composite

This paper reports on the electric field control of magnetism without magnetic bias field in a Ni/Pb(Mg1/3Nb2/3)O3-PbTiO3/Ni composite prepared by electrochemical deposition. The converse magnetoelectric effect, which was measured by an induction method, shows a peak value of 0.45 G/V at the resonance frequency of 102 kHz. Without magnetic bias field, the magnetization of the Ni layers can be controlled by an applied dc electric field in a reversible and reproducible way and shows an analogous on-off behavior with the electric field switching on and off alternatively.

Magnetization switching in the BiFe0.9Mn0.1O3 thin films modulated by resistive switching process

Polycrystalline BiFe0.9Mn0.1O3 thin films have been prepared on Pt/Ti/SiO2/Si wafers by a sol-gel process. The film exhibits typical resistive switching (RS) effect. Moreover, accompanied with the RS process, remarkable magnetization switching (MS) behaviors happen, i.e., at low resistance state the film shows high saturation magnetization, while showing low saturation magnetization at high resistance state. We revealed that such a MS effect mainly originates from the conversion of Fe ion valence state between Fe2+ and Fe3+ during the RS process, which was confirmed by the x-ray photoelectron spectroscopy measurements. The further first-principle calculations showed that the doping of Mn into the BiFeO3 could induce an impurity energy level which makes it facile to achieve the conversion of Fe ion valence state. Based on the conductive filament model, a possible mechanism of tuning the MS effect by RS process is proposed, which is closely related to the conversion of Fe ion valence state along with the fo...

Transition of recollision trajectories from linear to elliptical polarization.

Using a classical ensemble method, we revisit the topic of recollision and nonsequential double ionization with elliptically polarized laser fields. We focus on how the recollision mechanism transitions from short trajectories with linear polarization to long trajectories with elliptical polarization. We propose how this transition can be observed by meansuring the carrier-envelop-phase dependence of the correlated electron momentum spectra using currently available few-cycle laser pulses.

Anisotropic manipulation of ferroelectric polarization in SrTiO3/(Co0.9Zn0.1)Fe2O4 heterostructural films by magnetic field

Multiferroic SrTiO3/(Co0.9Zn0.1)Fe2O4 (STO/CZFO) films with preferential crystallographic orientations were prepared by a sol-gel process. The films exhibited evident ferroelectricity and well-defined ferromagnetic characteristics with certain magnetic anisotropy. Remarkable suppression of ferroelectric polarization by in-plane magnetic field and great enhancement under out-of-plane magnetic field were realized, and large anisotropic magnetodielectric effect was observed. We showed that the ferroelectric polarization of the whole film was closely related to the defect dipoles in the STO layer. Based on the model where the dissociation or formation of defect dipoles is associated with the volume change of STO unit cells, we elucidated the mechanism of anisotropic magnetic-manipulation of ferroelectric polarization for the films, and attributed it to the rearrangement of oxygen vacancies in the STO layer, which was controlled by the ferromagnetic CZFO layer through interface coupling under external magnetic...

Manipulating the exchange bias effect of Pb(Zr0.52Ti0.48)O3/CoFe2O4/NiO heterostructural films by electric fields

The Pb(Zr0.52Ti0.48)O3/CoFe2O4/NiO heterostructural films with exchange bias (EB) effect have been prepared on Pt/Ti/SiO2/Si wafers using a sol-gel process, and reversible manipulation of EB effect by electric fields has been realized. Compared with the exchange bias field (Heb = −75 Oe) at as-grown state, the modulation gain of Heb by electric fields can reach 83% (Heb = −12.5 Oe) in the case of +5.0 V and 283% (Heb = −287.5 Oe) in the case of −5.0 V, respectively. Moreover, such electrically tunable EB effect is repeatable and has good endurance and retention. Through analyzing the energy band structures in different electric treatment states, we discuss the mechanism of such electric-field-tunable EB effect. Two factors, i.e., the filling (or releasing) of electrons into (or from) the defect levels produced by oxygen vacancies at positive (or negative) electric voltages, and the redistribution of electrons due to the ferroelectric polarization, both of which give rise to the variation of the strength of exchange interaction in the CFO layer, have been revealed to be responsible for the electric modulation of EB effect. This work provides a promising avenue for electrically manipulating the EB effect and developing high-performance memory and storage devices with low power consumption.

Preparation of YBa sub 2 Cu sub 3 O sub 7 minus. delta. thin films by magnetron sputtering with in situ plasma oxidation

Superconducting YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} thin films with surface roughness Ra{similar to}20 A have been successfully prepared by either rf or dc magnetron sputtering. The substrate temperature was kept at 600--670 {degree}C during deposition and a subsequent {ital in} {ital situ} plasma oxidation treatment was performed at 480--520 {degree}C. The films deposited on single-crystal SrTiO{sub 3} (100) exhibited zero resistance at 91 K and had the critical current density of 3{times}10{sup 6} A/cm{sup 2}. In this paper we describe the influences of fabrication conditions on film superconductivity.

Manipulating the magnetism and resistance state of Mn:ZnO/Pb(Zr0.52Ti0.48)O3 heterostructured films through electric fields

Mn:ZnO/Pb(Zr0.52Ti0.48)O3 (PZT) heterostructured films have been prepared on Pt/Ti/SiO2/Si wafers by a sol-gel process. Nonvolatile and reversible manipulation of the magnetism and resistance by electric fields has been realized. Compared with the saturation magnetic moment (Ms) in the +3.0 V case, the modulation gain of Ms can reach 270% in the −3.0 V case at room temperature. The resistance change is attributed to the interfacial potential barrier height variation and the formation of an accumulation (or depletion) layer at the Mn:ZnO/PZT interface, which can be regulated by the ferroelectric polarization direction. The magnetism of Mn:ZnO originates from bound magnetic polarons. The mobile carrier variation in Mn:ZnO, owing to interfacial polarization coupling and the ferroelectric field effect, enables the electric manipulation of the magnetism in the Mn:ZnO/PZT heterostructured films. This work presents an effective method for modulating the magnetism of magnetic semiconductors and provides a promising avenue for multifunctional devices with both electric and magnetic functionalities.Mn:ZnO/Pb(Zr0.52Ti0.48)O3 (PZT) heterostructured films have been prepared on Pt/Ti/SiO2/Si wafers by a sol-gel process. Nonvolatile and reversible manipulation of the magnetism and resistance by electric fields has been realized. Compared with the saturation magnetic moment (Ms) in the +3.0 V case, the modulation gain of Ms can reach 270% in the −3.0 V case at room temperature. The resistance change is attributed to the interfacial potential barrier height variation and the formation of an accumulation (or depletion) layer at the Mn:ZnO/PZT interface, which can be regulated by the ferroelectric polarization direction. The magnetism of Mn:ZnO originates from bound magnetic polarons. The mobile carrier variation in Mn:ZnO, owing to interfacial polarization coupling and the ferroelectric field effect, enables the electric manipulation of the magnetism in the Mn:ZnO/PZT heterostructured films. This work presents an effective method for modulating the magnetism of magnetic semiconductors and provides a promisi...