Comparative Study of the Electronic Properties of Hexagonal and Orthorhombic Structures of RMnO₃-Type Perovskites (R=Tb, Dy, Ho and Er) by DFT Calculations

The electronic properties of perovskite RMnO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>(R=Tb, Dy, Ho and Er) were studied using the density-functional theory (DFT). For each perovskite RMn O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>, the ferromagnetic (FM) and antiferromagnetic (AFM) structural parameters in the spin-up and spin-down configurations are optimized. The band structures, the density of states (DOS) and the partial density of states (PDOS) of the hexagonal (h-RMO) and orthorhombic (o-RMO) are also investigated. As results, a relationship between the crystal structures and their electrical behavior has been established: the orthorhombic structure exhibits semiconducting behavior with bandgap ranging from 0.5 to 0.7 eV; the hexagonal structure in the spin-down configuration exhibits semiconducting behavior with a bandgap ranging from 2.4 to 2.7 eV; the hexagonal structure with an earth rare element having a small ionic radius (Tb and Dy in the present case) in the spin-up state exhibits semiconducting behavior with a bandgap of about 0.6 e V; the hexagonal structure with an earth rare element having a high ionic radius (Ho and Er in the present case) in the spin-up state exhibits metallic behavior.