Coexistence of ferroelectricity and ferromagnetism in hex-GeS nanowires.

The existence of one-dimensional (1D) ferroelectricity and ferromagnetism provides an opportunity to expand the field of research in low-dimensional magnetoelectric and multiferroics and explore the future development of high-performance nanometer devices. Here, we predict a novel 1D ferroelectric hex-GeS nanowire with coexisting ferromagnetism. The electric polarization comes from the atomic displacements between Ge and S atoms, and it exhibits a far-higher than room temperature ferroelectric Curie temperature T Ec = 830 K. The ferromagnetism, stemming from the Stoner instability, can be tuned by hole doping and maintained over a wide range of hole concentrations. Additionally, an indirect-direct-indirect band gap transition can be achieved via strain engineering and the bonding nature of the near-band-edge electronic orbitals revealed this transition mechanism. These results offer a platform to investigate 1D ferroelectric and ferromagnetic systems, and the presented hex-GeS nanowire demonstrates the potential for high-performance electronic and spintronic applications.