Jinshuai Wang

Temperature dependence of polarization switching properties of Bi3.15Nd0.85Ti3O12 ferroelectric thin film

The temperature dependences of the polarization switching properties of Bi3.15Nd0.85Ti3O12 (BNT) ferroelectric thin film in the range from 25 to 150°C have been investigated. With increasing temperature, the switchable polarization and switching time decrease. Meanwhile, the depolarization field due to the interfacial layer between the electrode and the BNT film increases with increasing temperature, which induces more domain back-switching. In addition, the local switching properties of BNT film have been studied using piezoresponse force microscopy, and it is found that the prepared BNT film has good local switching behaviors.

Effects of space charge distribution on ferroelectric hysteresis loops considering the inhomogeneous built-in electric field: A phase field simulation

A phase field model based on the time-dependent Ginsburg-Landau equation is developed to investigate the space charge distribution effects on the ferroelectric hysteresis characteristics of the ferroelectric thin film, in which the inhomogeneity of the built-in electric field (Eib) distribution along the vertical direction of ferroelectric thin film and the corresponding effect on the domain kinetics are taken into account. The hysteresis loops of the ferroelectric thin films with different space charge distributions are calculated by using this model. The results indicate that symmetrically (including homogeneously) distributed space charges lead to the hysteresis loop constriction because the Eib weakens the total electric field to make the ferroelectric film form a stable monodomain structure or the 180° strip domain. However, asymmetrically distributed space charges cause not only the shift but also the distortion of the hysteresis loop which is pinched in one head and loses its centrosymmetry. This i...

Effect of surface tension on electrocaloric effects in the ferroelectric nanomaterial with vortex domain structures

The influence of intrinsic surface tension on the electrocaloric effect (ECE) in the ferroelectric nanomaterial with vortex domain structures is studied by using the phase field method. The calculation results show that a giant adiabatic temperature change (ΔTu2009=u20095.8u2009K) related to the toroidal moment change appears in the PbTiO3 (PTO) ferroelectric nanoparticle with the surface tension coefficient μu2009=u20095u2009N/m under the vorticity vector of curled electric field (Q1u2009=u20090u2009mV/A2, ΔQ1u2009=u20090.9u2009mV/A2) at room temperature. The magnitude of the adiabatic temperature change decreases with the increase in surface tension. The decrease in size is found to enhance the ECE of PTO nanoparticle with vortex domain structures when the surface tension is not considered.

Topological trajectories of a magnetic skyrmion with an in-plane microwave magnetic field

Magnetic skyrmions are stable and topologically protected spin textures which have been observed in several chiral magnetic materials, and the resonant excitations of magnetic skyrmions have become a hot research topic for potential applications in future microwave devices. In this work, we investigate in-plane microwave-induced topological dynamics of a magnetic skyrmion in a nanodisk by using micromagnetic simulations. It is found that the resonant excitations of the skyrmion are elliptical dynamics which contain counterclockwise and clockwise modes by applying different frequencies of the microwave field. The conversion between these two elliptical modes is achieved by a transition to linear vibration. In addition, we demonstrate that the off-centered process of the skyrmion can be controlled by applying different phases of the microwave field. Finally, we discuss the different topological excitations of four types of skyrmions. Our results present the understanding of topological skyrmion dynamics and...

Influence of 90° charged domain walls on the electrocaloric effect in PbTiO3 ferroelectric thin films

The electrocaloric (EC) effect in PbTiO3 ferroelectric thin films (FETFs) with an array of partially compensated head-to-head (HH) and tail-to-tail (TT) 90° charged domain walls (CDWs) has been studied by using a phase field method. The calculation results indicate that the magnitude of the adiabatic temperature change ΔT increases with the diminution of the charge density (ρ*), in which ρ* is provided by charged defects or band bending. In particular, a negative EC effect caused by the direction difference between the applied electric field and the dipole is found near the HH and TT domain walls when ρ*u2009>u20092.0. The EC strength | ΔT |/| ΔE | is 0.020u2009Ku2009cmu2009kV−1 with the positive ΔTu2009=u20092.03u2009K at the external dimensionless electric field Eb*=0.08 (ΔEu2009=u2009104u2009kVu2009cm−1). These results indicate that the CDWs can provide an efficient way to adjust the EC effect of FETFs for refrigeration applications at room temperature.

Giant negative electrocaloric effect in PbZrO3/0.88BaTiO3–0.12Bi(Mg1/2,Ti1/2)O3 multilayered composite ferroelectric thin film for solid-state refrigeration

A giant negative electrocaloric (EC) effect in a PbZrO3/(0.88BaTiO3–0.12u2009Bi(Mg1/2,Ti1/2)O3) (PZ/(BT-BMT)) multilayered composite ferroelectric (MCFE) thin film which is grown on Pt(111)/Ti/SiO2/Si(100) substrates by the sol-gel method is investigated in this work. The negative EC effect in the PZ/(BMT-BT) MCFE thin film is greatly higher than that in the PZ AFE thin film with an adiabatic temperature change (ATC) ΔTu2009=u20091.5u2009K. The ATC ΔT of the PZ/(BMT-BT) MCFE thin film is −32u2009K under the applied electric field change ΔEu2009=u20091151u2009kV/cm. The result is conducive to enhance the EC refrigeration efficiency greatly.A giant negative electrocaloric (EC) effect in a PbZrO3/(0.88BaTiO3–0.12u2009Bi(Mg1/2,Ti1/2)O3) (PZ/(BT-BMT)) multilayered composite ferroelectric (MCFE) thin film which is grown on Pt(111)/Ti/SiO2/Si(100) substrates by the sol-gel method is investigated in this work. The negative EC effect in the PZ/(BMT-BT) MCFE thin film is greatly higher than that in the PZ AFE thin film with an adiabatic temperature change (ATC) ΔTu2009=u20091.5u2009K. The ATC ΔT of the PZ/(BMT-BT) MCFE thin film is −32u2009K under the applied electric field change ΔEu2009=u20091151u2009kV/cm. The result is conducive to enhance the EC refrigeration efficiency greatly.

Skyrmion-based multi-channel racetrack

Magnetic skyrmions are promising for the application of racetrack memories, logic gates, and other nano-devices, owing to their topologically protected stability, small size, and low driving current. In this work, we propose a skyrmion-based multi-channel racetrack memory where the skyrmion moves in the selected channel by applying voltage-controlled magnetic anisotropy gates. It is demonstrated numerically that a current-dependent skyrmion Hall effect can be restrained by the additional potential of the voltage-controlled region, and the skyrmion velocity and moving channel in the racetrack can be operated by tuning the voltage-controlled magnetic anisotropy, gate position, and current density. Our results offer a potential application of racetrack memory based on skyrmions.