Structure, half-metallic and magnetic properties of bulk and (001) surface of Rb₂XMoO₆ (X = Cr, Sc) double perovskites: a DFT + U study

Abstract

Half-metallic (HM) ferromagnets (HM-FMs) with large HM gap and high Curie temperature (TC) have a great importance in the field of spintronics. In this study, the geometric features, electronic structure and magnetism of two new double perovskites (DPs) represented by Rb2XMoO6 (X=Cr, Sc) were explored in bulk phase and (001) surface using quantum mechanical total energy calculations based on density functional theory (DFT). The results showed that Rb2CrMoO6 (RCMO) and Rb2ScMoO6 (RSMO) has an optimized lattice constant of 7.96Å and 8.26 Å, respectively, in the cubic phase (Fm-3m, #225). The cohesive energy Ecoh, formation energy Efor and elastic constants (mechanical) calculations proved that materials are stable. The magnetic properties explored in terms of ground state magnetic coupling, total magnetic moment (M) and atomic magnetic moment (m), exchange energy (J), and Curie temperature. It was found that both materials have ferromagnetic coupling in the ground state, with M of integer value of 8.0 µB (4.0 µB), J value of 47 meV(72 meV) and TC of 365 K (557 K) in Rb2CrMoO6 (Rb2ScMoO6). The electronic properties computed with electronic band structure and density of states demonstrated both DPs to be half-metal with HM gap of 1.61 eV (2.1 eV) in Rb2Cr-based (Rb2Sc-based) system. Finally the electronic and magnetic properties of (001) surfaces were investigated and compared with that of bulk phase. Interestingly, bulk HM property was retained in RSMO, but disappeared in RCMO due the emergence of defect states at Fermi level (EF). The reported results suggest that Rb-based DPs carry some fascinating properties for spin-based devices.

First-principles investigation of the structural stability, electronic, and thermodynamic properties of Ba2NaHaO6 (Ha = Cl, Br, I) periodate double perovskites

“…Cohesive and formation energies are useful chemical properties for analyzing the strength of atomic forces that hold solids together and revealing the phase stability of any material. 66–70 The formation energy of a material is calculated by subtracting the sum of energies of the individual constituent atoms from the equilibrium energy of the primitive cell of that material divided by the total number of atoms in the primitive cell as described in eqn (18).Here, E b x ( x = Ba, Na, O, Cl, Br, I) are the bulk elemental energies calculated as per atom from the stable bulk phase of each element; 71 e.g. , we have used cubic Ba, cubic Na, trigonal O, orthorhombic Cl, cubic Br, and cubic I bulk structures, which have 4, 1, 6, 8, 3, and 2 atoms per cell, respectively.…”

“…Mebed et al calculated the cohesive and formation energies for Rb 2 CrMoO 6 as +4.531 and −1.887 in eV per atom, and for the Rb 2 ScMoO 6 DP structure as +5.065, and −1.826 in eV per atom, respectively. 71 Mir et al reported the cohesive energies of Ca 2 MgWO 6 and Sr 2 MgWO 6 DP oxides as 6.18 and 5.74 eV per atom, respectively. 75 Manzoor et al calculated the formation energies for the Sr 2 SbTaO 6 DP structure as −2.886 eV per atom and for Sr 2 BiTaO 6 DP oxide as −2.798 eV per atom.…”

“…Moreover, this implies that the reaction will be exothermic. 67,68,[71][72][73] When the cohesive energy of a structure is higher, it is generally more stable. A more negative formation energy indicates a more stable structure.…”

Investigation of ultra wide bandgap Flouro-perovskite materials RBeF3 (R K and Li) for smart window applications: A DFT study

“…Unique fluoro-perovskites keep showing a wide range of remarkable properties, such as ongoing advanced technology applications and the ability to incorporate almost all elements of the periodic table K 2 CuBiCl 6 [ 19 ], Rb 2 CrMoO 6 [ 20 ], and Rb 2 GeSnI 6 [ 21 ], which makes their study fascinating. Highly mobile fluoro-perovskite RBeF 3 (R K and Li) layers are of particular interest as they reflect solar UV radiation and provide new layer components and broad bandgap substances for light reflection.…”