Magnetic properties and Mossbauer studies of Gd1-xSrxFeO3-y (x=0.25, 0.75)

Perovskite Gd1-xSrxFeO3-y (x = 0.25 and 0.75) powders have been studied by X-ray diffraction, Mohr's salt analysis, vibrating sample magnetometer, and Mossbauer spectroscopy. X-ray diffraction patterns show that their crystal structures are orthorhombic for x = 0.75 and cubic for x = 0.75. Fe-57 Mos sbauer spectra of the Gd1-xSrxFeO3-y have been taken at various temperature s ranging from 4.2 to 850 K. It is found that Neel temperatures for x = 0.2 5 and 0.75 are 685 and 270 K. respectively. Mossbauer spectra of Gd0.75Sr0. 25FeO3-y powders have been taken at various temperatures ranging from 13 to 620 K. The Neel temperature decreases with the increase of the Sr concentr ation, which suggests that the superexchange interaction for Gd-Fe-O-Fe is stronger than that for Sr-Fe-O-Fe. Mossbauer spectrum at 13 K consists of m agnetic sextet components arising from different charge states of iron ions . In the orthorhombic phases (x = 0.25), the charge states coexist Fe3+ and Fe4+(high spin) and the charge states coexist Fe3+ and Fe4+(low and high s pin) in the cubic phases (x = 0.75). Magnetic susceptibility measurements b y using a vibrating sample magnetometer show that Gd1-xSrxFeO3-y behavior i s weak-ferromagnetic due to canted spin for x = 0.75 and antiferromagnet fo r x = 0.25. (C) 2000 Elsevier Science B.V. All rights reserved.