Synthesis, structure and magnetic properties of a novel double layered brownmillerite Ca2LaFe1.75Cr0.25GaO8

Abstract We report the structural and magnetic properties of a novel double layered Brownmillerite Ca2LaFe1.75Cr0.25GaO8. Synchrotron X-ray diffraction and neutron powder diffraction data confirms orthorhombic structure having Pbma space group with tetrahedral chain ordering and ∼ 25 % of cation (Fe/Ga) disorder between octahedral and tetrahedral sites. Ca2LaFe1.75Cr0.25GaO8 exhibits antiferromagnetic transition at TN∼630 K. The magnetic structure is determined as canted G-type antiferromagnetic with weak ferromagnetic component along a direction. The ordered magnetic moments obtained at 4 K are 2.24 (4) µB (Fe3+/Cr3+) for octahedral sites and 2.34 (4) µB (Fe3+) for tetrahedral sites.