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Magnetoelectric heterojunction properties of multiferroic materials

Özdilek, Çağrı
Bismuth ferrite (BiFeO3) has gained a great interest over the past years as it exhibits more than one primary ferroic orders in a single phase. In the first part of this work, optimum parameters, such as reaction temperature, duration and concentration of mineralizer in the solution, for the production of bismuth ferrite particles via a hydrothermal method were determined. The second part involves the influence of Yb doping on the structural, magnetic and electrical properties of bismuth ferrite (BiFeO3). Well-crystallized BiFeO3 (BFO) and Yb-doped BiFeO3 powders (Bi1-xYbxFeO3: x = 0, 0.01, 0.03, 0.05, 0.1) were successfully synthesized via a typical hydrothermal method. X-ray diffraction (XRD) revealed that powders have a distorted rhombohedral structure with a space group of R3c. Field emission scanning electron microscope (FESEM) studies indicated more or less cuboidal particles consisting of subparticles with different sizes. It was found that increase in Yb content retains the particle growth, therefore, reduces the size of these cuboidal particles. X-ray photoelectron spectroscopy (XPS), on the other hand, showed the presence of oxygen content in the lattice which was increased from 7.04% to 39.97% in doped BiFeO3 powders, indicating that doping with Yb reduces oxygen deficiencies in the lattice and ensures the formation of more M-O-M bonds. Vibrating sample magnetometer (VSM) measurements revealed that the highest saturation magnetization value was achieved as 0.09 emu/g for 3 at% Yb-doped BFO showing weak ferromagnetic behavior. Ferroelectric measurements were also conducted to find remanent polarization (Pr) values of samples. Among all samples, the highest Pr value, 0.37 μC/cm2, was attained for 3 at% Yb-doped BFO. From dielectric measurements, it was proved that incorporation of Yb into BiFeO3 perovskite structure enhances formation of M-O-M bonds, therefore, the highest dielectric constant and lowest dielectric loss were achieved in case of Bi0.9Yb0.1FeO3.