Q.F. Li

First-principles investigations of disorder effects on electronic structure and magnetic properties in Sr2CrMoO6

The electronic structures and magnetic properties are reported for ordered and disordered Sr2CrMoO6 presenting oxygen vacancies or/and antisite defects (ASs). We investigate the stability of an antiparallel (AP) magnetic moment on Cr antisites and the calculations show that these solutions are more stable relative to the parallel solution for AS defects with or without oxygen vacancies. Electronic band structure calculations indicate that the perfect Sr2CrMoO6 is half-metallic, and the half-metallic character is preserved for Sr2CrMoO6 containing only oxygen vacancies, while the half-metallic nature is destroyed when 25% ASs (50% ASs) with or without oxygen vacancies is present. For 25% ASs with two oxygen vacancies, the system possibly shows nonmetallic behavior. The experimentally observed reduction of the magnetic moment mainly arises from an antiferromagnetic coupling of Cr–O–Cr (Cr–Cr) bonds in a disordered sample.

First-principles study of the electronic and magnetic properties of Sr2Fe1+xMo1−xO6

We have investigated the electronic and magnetic properties of Sr2Fe1+xMo1−xO6 (−1≤x≤0.25), the composition x = 0 corresponding to the well-known double perovskite system Sr2FeMoO6, using first-principles density functional theory within the generalized gradient approximation (GGA)+U schemes. The crystal structure of the compounds has a cubic lattice for x = −1 and 0.25 while the structure of the compounds has a tetragonal lattice from x = −0.75 to 0.0. The lattice parameters decrease slightly as the Fe content increases and the variation of unit cell volume is linear with the composition x. Our spin-polarized calculations give a metallic ground state for the x<0 regime and a half-metallic ground state for the x≥0 regime. The magnetic structures for x≤0 are found to be the ferromagnetic state while the magnetic structure for x = 0.25 is the ferrimagnetic state where any Fe at the Mo crystallographic site is coupled antiparallel to the Fe moments at the correct site.

ELECTRON DOPING EFFECTS ON ELECTRONIC AND MAGNETIC PROPERTIES IN Sr2FeReO6

We have investigated the electronic and magnetic properties of electron-doped Sr2-xLaxFeReO6 (x = 0.0, 0.25, 0.5) using first-principles density functional theory within the generalized gradient approximation (GGA) and GGA + U schemes. Our results reveal that the symmetry of the La-doped compounds is decreased from tetragonal I4/m for perfect sample to monoclinic P21/n. With increasing La content the absolute magnetic moment of the Re site increases distinctly and the doped electrons are considered to occupy mainly the down-spin Re 5d band from the band calculation. Electronic doping is found to enhance the Curie temperature (Tc) and stabilize the ferromagnetic half-metallic ground states of Sr2FeReO6. And it is found that the increase of Tc is mainly caused by the increase of ferromagnetic interaction between the Fe–O–Fe.