L.J. Ding

Half-metallic ferromagnetism in wurtzite ScM (M=C, Si, Ge, and Sn): Ab initio calculations

Using the full potential linearized augment plane wave method with the modified Becke and Johnson (mBJ) potential, the half-metallicity and electronic structure for the wurtzite ScM (M = C, Si, Ge, and Sn) compounds are investigated. The ScM series compounds are found to be excellent half-metallic ferromagnets (HMFs) with large half-metallic gaps (0.76–0.33 eV). The magnetic moments are 2.00 μB per cell, and p-d hybridization mechanism plays crucial role in forming the half-metallic ferromagnetism. The ferromagnetic ground states, larger half metallic gaps, the robust half-metallicity with respect to the lattice compression, negative cohesive energy, and heat of formation indicate ScM compounds would be promising HMFs.

Electronic structure and ferromagnetism of boron doped bulk and surface CdSe: By generalized gradient approximation and generalized gradient approximation plus modified Becke and Johnson calculations

Using the full potential linearized augment plane wave method with the generalized gradient approximation (GGA) and GGA plus modified Becke and Johnson (GGA+mBJ) potential, the electronic structures and ferromagnetism for the boron doped bulk and surface CdSe are investigated. Calculations show that the substitutional boron for selenium in CdSe could induce spin polarized localized states in the gap and generate local magnetic moments 3.00 μB with one dopant atom. Energy difference between the antiferromagnetic and ferromagnetic phase suggests that BSe favors the ferromagnetic ground state. Electronic structures indicate the magnetic moments mainly provided by the doped boron atoms, and carriers mediated double exchange mechanism plays crucial role in forming the ferromagnetism. Ferromagnetic boron doped CdSe (100) films could be realized by using the high energy boron ions injection to form the non-surface doped configurations. The cadmium vacancy would reduce the ferromagnetism and lead the boron doped ...

A theoretical model for anisotropic multiferroics

We propose a theoretical model for anisotropic multiferroics, which are one-dimensional charge transfer magnets. By means of Greens function theory, ferroelectric and magnetic properties are studied. It is found that the anisotropy not only plays an important role on the ferroelectric phase transition but also enhances the ferroelectric polarization. Under different anisotropy, the phase diagram and temperature dependence of the magnetic susceptibility and dielectric constant are also presented. It reveals that the transition temperature increases as anisotropy ascends, which is attributed to the energy gap. These results put forward a way to enhance the ferroelectric phase transition temperature.

Enhanced electrocaloric effect in displacive-type organic ferroelectrics

We explore the intrinsic feature of electrocaloric effect (ECE) accompanied by ferroelectric (FE)-paraelectric (PE) transition for displacive-type organic ferroelectrics using Greens function theory. It is demonstrated that decreasing elastic constant K or increasing spin-lattice coupling λ can enhance the ECE, as well as polarization P and transition temperature TC. Indeed, one expects that the optimal operating temperature for solid-state refrigeration is around room temperature, at which the ECE achieves its maximum. As TC is tuned to ∼310 K, it presents larger ECE response and remanent polarization with lower coercive field for smaller K value, suggesting that well flexible displacive-type organic ferroelectrics are excellent candidates both for electric cooling and data storage in the design of nonvolatile FE random-access memories. Furthermore, in an electric field, it provides a bridge between a Widom line that denotes FE-PE crossover above TC and a metaelectric transition line below TC that demon...

Approach to control polarization and magnetic properties for multiferroics with Dzyaloshinskii-Moriya interaction

We propose a theoretical model for one-dimensional (charge transfer magnets with Dzyaloshinskii-Moriya (DM) interaction. By using Greens function theory, we have studied the effect of DM interaction on ferroelectric and magnetic properties, where ferroelectricity is induced through symmetric mechanism. It is shown that the uniform DM interaction reduces the polarization and makes the magnetization plateau narrow down. Moreover, the transition temperature descends as the uniform DM interaction ascends, which is attributed to the decrease of the energy gap. In addition, the staggered DM interaction, which is related to intersite distance, is also discussed. It is also found that there exists a critical point, above or below which the staggered DM interaction plays different roles on the polarization, transition temperature, and magnetic behavior. As the staggered DM interaction is larger, it enhances the polarization and transition temperature and meanwhile widens the magnetization plateau, otherwise it re...