Magnetism and multiferroic properties at MnTiO3 surfaces: A DFT study

Abstract

The present study illustrates how density functional theory calculations can rationalize the surface structure and magnetism for the low-index (1 1 0), (1 0 1), (1 0 0), (0 0 1), (1 1 1), and (0 1 2) surfaces of MnTiO 3. A simple procedure, without surface reconstructions or chemical adsorptions in which the stability, magnetism and the morphological transformations is presented in detail to clarify the control of their multiferroic nature. The surface stability was found to be controlled by the octahedral [MnO 6 ] and [TiO 6 ] clusters formed by the Mn 2+ and Ti 4+ cations-i.e., their local coordination at the surfaces, respectively-with nonpolar (1 1 0) being the most stable. Enhanced superficial magnetism was found for (0 1 2), (0 0 1), and (1 1 1) surfaces in agreement with the more undercoordinated [TiO n ]′ and [MnO n ] • complex clusters at the surface plane. Our calculation suggests the existence of magnetic [TiO n ]′ species for unstable (0 0 1) and (1 1 1) surfaces, explained by the unusual crystal-field associated with the surface environment. The crystal morphology has been predicted to determine the most likely terminations to be present as well as the intrinsic magnetization density associated with morphologies. Moreover, the (0 0 1) surface plane plays a key role in the enhancement of the magnetic properties for shape-oriented MnTiO 3 nanoparticles, suggesting a superior magnetoelectric coupling due to the presence of uncompensated spins and polar distortions perpendicular to the surface plane.

A broad theoretical investigation of R‐3, R3c, and R‐3c polymorphs of FeCrO3

“…However, our results have evidenced that the ilmenite bulk presented an AFM overall magnetism, being the same ordering observed for (001) surface; thus, the residual magnetism observed was caused by a morphology magnetization. Our morphology magnetization hypothesis has been based on other theoretical results for similar materials 54,64,65 . Consequently, an AFM order is expected for the same surface of R 3 c polymorphs.…”

“…Hence, the cleavage energy for relaxed surfaces ( ) was obtained from Equations and . This methodology is very representative and has been successfully applied to investigate the surface properties of several materials 54,55,63‐66 . Thus, the obtained surfaces for LNO‐, ilmenite‐ and corundum‐type are Cr–O 3 –Pb–Ni–O 3 –Fe [18 layers], Fe–O 3 ‐Cr 2 –O 3 –Fe [6 layers], and Fe–O 3 –Cr–Fe–O 3 – Cr [4 layers] respectively. …”

“…This methodology is very representative and has been successfully applied to investigate the surface properties of several materials. 54,55,[63][64][65][66] Thus, the obtained surfaces for LNO-, ilmenite-and corundum-type The magnetic properties of each surface were evaluated by a similar approach to that applied top the bulk magnetism. However, the Ising Hamiltonian limitation prevents their application to study of materials with a high number of non-equivalent positions, as observed on solid-state surfaces cut.…”

Reading at exposed surfaces: theoretical insights into photocatalytic activity of ZnWO4

“…Therefore, theoretical models and computer simulations must be developed to investigate the surface energy at the nanoscale. Because of the Wulff construction, the equilibrium morphology of a given material can be obtained using ab initio calculations [131][132][133][134][137][138][139][140][141][142] . The procedure to obtain the complete set of morphologies, based on the Wulff construction and the surface energy, has been previously presented and employed as guide to match with experimental morphologies obtained for different binary oxides such as: Co 3 80 .…”

Ab initio Calculations of YAlO3 and ABO3 Perovskite (001), (011) and (111) Surfaces, Interfaces and Defects

“…Surface and interface phenomena, taking place in the ABO 3 perovskites as well as their nanostructures, the complex nature of their surface and interface states, the novel mechanisms of surface electronic processes are the key topics in nowadays solid state physics [1][2][3][4][5][6][7]. CaTiO 3 (CTO), SrTiO 3 (STO), PbTiO 3 (PTO), BaTiO 3 (BTO), SrZrO 3 (SZO) and PbZrO 3 (PZO) materials are so-called ABO 3 perovskites, and they have a large amount of technologically important applications, such as, for example, capacitors, actuators, and charge storage devices, and many others [8], for which the surface quality and structure are essential.…”