Effect of oxygen vacancies on the magnetic structure of the La0.6Sr0.4FeO3-δ perovskite:: A neutron diffraction study

Magnetic interactions in perovskite compounds of the type La1-xSrxMO3-delta (M=3d transition such as Mn and Fe) are presumed to arise through a super exchange between 3d electrons of the magnetic ions via oxygen orbitals. The magnetic structure of La0.6Sr0.4FeO3-delta has been studied with neutron diffraction. Oxygen vacancies were created by annealing samples under various gases including N-2, air and mixtures of CO/CO2. All La0.6Sr0.4FeO3-delta compounds maintain the rhombohedral structure (space group R (3) over barc). The air- or oxygen-annealed samples have almost no oxygen vacancies while those made in the reducing atmosphere show 7%-11% oxygen vacancies. The rhombohedral distortion decreases in the reduced samples. All the samples exhibit antiferromagnetic ordering at room temperature, although a small ferromagnetic moment may also be present. The samples with little or no oxygen vacancies show a room temperature magnetic moment of similar to1.4 mu(B) at the Fe site while those having >7% oxygen vacancies show a moment of similar to4.0 mu(B). Magnetization measurements reveal a much higher magnetic ordering temperature in samples with oxygen vacancies. (C) 2002 American Institute of Physics.