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Electromechanical coupling factor, k, of piezoelectric materials determines the conversion efficiency of mechanical to electrical energy or electrical to mechanical energy. Here, we provide an fundamental approach to design piezoelectric materials that provide near-ideal magnitude of k, via exploiting the electrocrystalline anisotropy through fabrication of grain-oriented or textured ceramics. Coupled phase field simulation and experimental investigation on <001> textured Pb(Mg1/3Nb2/3)O3-Pb(Zr,Ti)O3 ceramics illustrate that k can reach same magnitude as that for a single crystal, far beyond the average value of traditional ceramics. To provide atomistic-scale understanding of our approach, we employ a theoretical model to determine the physical origin of k in perovskite ferroelectrics and find that strong covalent bonding between B-site cation and oxygen via d-p hybridization contributes most towards the magnitude of k. This demonstration of near-ideal k value in textured ceramics will have tremendous impact on design of ultra-wide bandwidth, high efficiency, high power density, and high stability piezoelectric devices. "k" is the electromechanical coupling factor, and determines the efficiency of conversion between electrical and mechanical energy or vice-versa in piezoelectric materials. Here, Yan et al. present an optimization strategy for "k" via texturing and covalency tuning that results in "k" values comparable to that of single crystals. [ABSTRACT FROM AUTHOR]

Interfaces often exhibit unique electronic and magnetic properties that are not present in their bulk constituents. Understanding the atomic-level structure and properties of the interface is crucial for their technological applications. In this article, we report a first-principles study of the γ-FeSi2/Si(001) interface to unravel the atomic-level structure property relationship. An external electric field is included in our model to tune the properties of the interface. Based on our calculations, we found a modest application of an electric field (> 0.15 eV/Å) could stabilize a sixfold and sevenfold coordinated, spin-active interface over a nonmagnetic (eightfold coordinated) interface-providing direct evidence of electric field control of magnetism at the interface. The sixfold as well as sevenfold coordinated structures are shown to favor antiferromagnetic spin ordering arising from the Fe(d)-Si(p)-Fe(d) super-exchange interaction. The distinct non-linear response of the interface structure to the applied electric field can be attributed to the different electronic and magnetic structures at the interface; the sixfold exhibits the highest polarizability over the other coordinated structures. [ABSTRACT FROM AUTHOR]

The electrical modulation of magnetization through the magnetoelectric effect provides a great opportunity for developing a new generation of tunable electrical components. Magnetoelectric voltage tunable inductors (VTIs) are designed to maximize the electric field control of permeability. In order to meet the need for power electronics, VTIs operating at high frequency with large tunability and low loss are required. Here we demonstrate magnetoelectric VTIs that exhibit remarkable high inductance tunability of over 750% up to 10 MHz, completely covering the frequency range of state-of-the-art power electronics. This breakthrough is achieved based on a concept of magnetocrystalline anisotropy (MCA) cancellation, predicted in a solid solution of nickel ferrite and cobalt ferrite through first-principles calculations. Phase field model simulations are employed to observe the domain-level strain-mediated coupling between magnetization and polarization. The model reveals small MCA facilitates the magnetic domain rotation, resulting in larger permeability sensitivity and inductance tunability. Voltage tunable inductors (VTIs) with high working frequency and tunability are desired for new design of energy efficient electronics. Here the authors demonstrate magnetoelectric VTIs operating up to 10 MHz with tunability over 750% via strain mediated magnetoelectric effect and magnetocrystalline anisotropy cancellation strategy. [ABSTRACT FROM AUTHOR]