Structural transformation and magnetic competition in Yb(Mn1-xFex)O3

Abstract

Structural and magnetic properties of the Yb(Mn1−xFex)O3 (0⩽x⩽1) system have been systematically investigated. Initial samples were prepared via a sol-gel method. A pure hexagonal phase was only obtained for samples with x⩽0.5. With high-pressure annealing, a pure orthorhombic perovskite phase was achieved for all the compositions. The Fe57 Mössbauer spectrum for x=0.5 shows that only Fe3+ ions exist in the system; there was no evidence of chemical inhomogeneities. With increasing x, the Néel temperature TN increases for both hexagonal and orthorhombic phases. The orthorhombic Yb(Mn0.5Fe0.5)O3 shows an interesting weak ferromagnetic state in the temperature range of 239–298K, the ferromagnetism disappearing abruptly on cooling below Tt=239K. The transition at Tt appears to be a reorientation of the spin axis of a type-G antiferromagnetic order from the orthorhombic a axis to the b axis in the (010) plane.