The mutual controls of ferroelectricity and magnetism are stepping towards practical applications proposed for quite a few promising devices in which multiferroic thin films are involved. Although ferroelectricity stemming from specific spiral spin ordering has been reported in highly distorted bulk perovskite manganites, the existence of magnetically induced ferroelectricity in the correspondi...

Molecular ferroelectrics are currently an active research topic in the field of ferroelectric materials. As complements or alternatives of conventional inorganic ferroelectrics, they have been designed to realize various novel properties, ranging from multiferroicity and semiconductive ferroelectricity to ferroelectric photovoltaics and ferroelectric luminescence. The stabilizing of ferroelectr...

An universal microscopic mechanism to understand the interplay between the electric and magnetic degrees of freedom in noncollinear multiferroics is developed. In a system with a strong spin-orbit coupling, we show that there is a pure electric mechanism that the ferroelectricity is generated by noncollinear magnetism through an electric current cancellation process, which saves the pure electr...

We present a theoretical investigation of the anomalous ferroelectricity of mixed-stack charge transfer molecular crystals, based on the Peierls-Hubbard model, and rst principles calculations for its parameterization. This approach is rst validated by reproducing the temperature-induced transition and the electronic polarization of TTF-CA, and then applied to a novel series of hydrogenbonded cr...

Multiferroics, where two or more ferroic order parameters coexist, is one of the hottest fields in condensed matter physics and materials science. To search multiferroics, currently most researches are focused on frustrated magnets, which usually have complicated magnetic structure and low magnetic ordering temperature. Here, we argue that actually simple interatomic magnetic exchange interacti...

First-principles calculations are presented for the layered perovskite Ca3Mn2O7. The results reveal a rich set of coupled structural, magnetic, and polar domains in which oxygen octahedron rotations induce ferroelectricity, magnetoelectricity, and weak ferromagnetism. The key point is that the rotation distortion is a combination of two nonpolar modes with different symmetries. We use the term ...

Doping a "parent" antiferromagnetic Mott insulator in cuprates leads to short-range electronic correlations and eventually to high-Tc superconductivity. However, the nature of charge correlations in the lightly doped cuprates remains unclear. Understanding the intermediate electronic phase in the phase diagram (between the parent insulator and the high-Tc superconductor) is expected to elucidat...

Materials that combine coupled electric and magnetic dipole order are termed 'magnetoelectric multiferroics'. In the past few years, a new class of such materials, 'induced-multiferroics', has been discovered, wherein non-collinear spiral magnetic order breaks inversion symmetry, thus inducing ferroelectricity. Spiral magnetic order often arises from the existence of competing magnetic interact...

We report scanned probe characterizations of the ferroelectric phase transition in individual barium titanate (BaTiO3) nanowires. Variable-temperature electrostatic force microscopy is used to manipulate, image, and evaluate the diameter-dependent stability of ferroelectric polarizations. These measurements show that the ferroelectric phase transition temperature (TC) is depressed as the nanowi...

Flexible organic materials possessing useful electrical properties, such as ferroelectricity, are of crucial importance in the engineering of electronic devices. Up until now, however, only ferroelectric polymers have intrinsically met this flexibility requirement, leaving small-molecule organic ferroelectrics with room for improvement. Since both flexibility and ferroelectricity are rare prope...