Structural modulation and magnetic properties of hexagonal Ba(Ti1−xFex)O3−δ ceramics

This paper investigates the structural and magnetic properties of hexagonal Ba(Ti1−xFex)O3−δ (x=0.3 and 0.7) ceramics, synthesized with solid-state reaction method. Transmission electron microscope investigations reveal that structural phase separation featured by non-modulated and modulated phases is identified by the electron diffraction patterns taken along [0 0 1] zone axis in x=0.3 sample (BTF30). While for x=0.7 sample (BTF70), a pure phase with commensurate and incommensurate modulations at different directions is identified. The superstructure peaks observed in their X-ray diffraction patterns are verified by their individual commensurate modulation, qs=1/2 (31-2) in the modulated phase of BTF30 and q4,−1=4/9(3 0 4)–(0 0 1) in BTF70. In addition to the room-temperature weak ferromagnetism of BTF30 and paramagnetism of BTF70, spin glass transitions with Tf=3.4 K for the former and Tf=33.6 K for the latter are observed. On the basis of the structural characteristics, the influence of O1 and O2 vacancies on magnetic and dielectric properties of the doped system is discussed.