Mullite‐hexagonal di‐phase multiferroic behavior with enhanced ferromagnetism of (1−x)Bi₂Fe₄O₉−xBaFe₁₂O₁₉ composites

Abstract

Multiferroic (1Àx)Bi 2 Fe 4 O 9 ÀxBaFe 12 O 19 (x ¼ 0.07, 0.08, 0.10, 0.12, 0.15, 0.20) composites were prepared using microwave hydrothermal and microwave sintering methods. X-ray diffraction analysis of the composites revealed the formation of di-phase compounds with barium hexaferrite and mullite bismuth ferrite, respectively. SEM (scanning electron microscope) measurements on the sintered surfaces of the composites displayed the microsized of Bi 2 Fe 4 O 9 matrix and nano-sized BaFe 12 O 19 . The study of Dielectric and complex impedance exhibited the presence of grain and grain boundary effects, and a negative temperature coefficient of resistance in the materials. The ferroelectric hysteresis loops showed an obvious ferroelectric behavior. The M r was up to 19.09 emu g À1 (much larger than pure Bi 2 Fe 4 O 9 matrix), indicating that increasing BaFe 12 O 19 content could enhance the ferromagnetic properties. The value of M r /M s for all the samples was higher than 0.5 (especially, the maximum was up to 0.89) and it is preferred in many applications such as magnetic recording media of high density and permanent magnets.