Teoria do funcional de densidade aplicada a materiais multiferróicos de estrutura R3c para investigação das suas propriedades estruturais, vibracionais, elásticas, eletrônicas, ópticas, magnéticas e ferroelétricas

Abstract

The development of materials aiming technological applications has been the focus of several scientific manuscripts and, among investigated materials stands out the multiferroics, which are considered as the next generation of materials to smart devices development. The multiferroism consists on the simultaneous existence of a magnetic ordering and ferroelectric or ferroelastic properties in a same crystalline phase, being the most common kind of multiferroism observed between the ferroelectricity and the magnetics ordering and also known as magnetoelectric coupling. In this work, new multiferroic materials were proposed from A and B cations replacement in R3c structures by magnetic and non-magnetic atoms; the materials were evaluated by computational simulations based on Density Functional Theory. The investigated materials presents high stability under room condition and high pressures in R3c structures, as well as electronic and optical properties suggesting then as viable alternatives to development of electronic devices and photocatalytic process, such as water splitting and photodegradation. Moreover, the ferroelectric and magnetic properties are oriented on [111] and x ([100]) directions, respectively, showing an anisotropic behavior in the material. Thus, such properties are tangent each other indicating the control possibility from an electric field applied along [111] direction resulting on a magnetic response or from a magnetic field applied along x direction to obtain a ferroelectric response. Therefore, the obtained results clarify the molecular origin of the magnetoelectric coupling for R3c materials and any other crystalline structures since the coupling arises from the fact that the magnetism and ferroelectricity are tangent each other and, consequently, dependents, indicating the coupling between both properties. This work represents the first deep description of how the multiferroism can be affected by chemical modification and also the first report about the general properties of evaluated materials, indicating these materials as potential alternative to development of electronic devices and any application based on multiferroism or smart materials.