On the magnetic properties of the multiferroic ceramics Bi0.99Y0.01Fe1-xNixO3 (0.01⩽x⩽0.05)

Multiferroic ceramics of Bi0.99Y0.01Fe1-xNixO3 with 0.01⩽x⩽0.05 were synthesized by using a modified solid state reaction method. The crystalline structure and the morphology of the samples were investigated by X-ray diffraction (XRD) and by scanning electron microscopy (SEM). The addition of Y and Ni to the bismuth ferrite (BiFeO 3 ) was found to decrease the average grain size. Ac magnetic susceptibility and the zero-field-cooled (ZFC) and field-cooled (FC) magnetizations were measured for temperatures in the range 5⩽T⩽300  K. Hysteresis loops and an irreversible behavior in the temperature dependence of the magnetization not present in pure BiFeO 3 were observed in the doped samples. However, the ferromagnetism was found more likely to be due to the presence of small amounts of magnetite. Nevertheless, the determination of the amount of Fe 3 O 4 in these composite materials is important because it influences the magnetoelectric coupling which is important for some technological applications.