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Theoretical and experimental study of multiferroics BiFeO3 and Bi(1-x)HoxFeO3

The magnetoelectric materials have been studied due to the scientific chalenges and the very promissing possibility of applications in electronic devices.Bismuth ferrite (BFO) is one of the few room temperature magneto-electric multiferroics. Bismuth ferrite (BiFeO3) is one of the most studied multiferroic system with a large number of published articles. This is mainly because BiFeO3 material possesses both ferromagnetic and ferroelectric properties observed at room temperature, which opens great possibility for industrial and technological applications.The influence of Ho doping on the crystal structure and magnetic properties of bismuth ferrite (BFO) nanopowders was investigated. BiFeO3 and Bi1-xHoxFeO3 ultrafine nanopowderswere synthesized by the hydrothermal method. Here we use simple, low-cost and energy-saving hydrothermal method, which has advantages over the conventional methods. The diffraction pattern was recorded at room temperature and atmospheric pressure in the absence of any re-heating of the sample. A fitting refinement procedure using the Rietveld method was performed which showed the incorporation of Ho3+ ions in the BiFeO3 crystal lattice, where they substitute Bi3+ ions. All the samples belong to R3c space group. In addition, theoretical investigation using bond valence calculations have been performed in order to mimic pure and Ho doped BiFeO3 compounds produced in the experiment. Various BFO polymorphs were investigated as function of holmium concentration and final optimization of crystal structures has been performed on ab initio level using Density Functional Theory (DFT). Furthermore, electronic and magnetic properties of BiFeO3 were investigated using combination of experimental and theoretical methods. Magnetic behavior of synthesized materials was investigated by SQUID magnetometer in wide temperature interval (2-800 K). Splitting between the zero-field-cooled and field-cooled magnetization curves becomes more pronounced as the Ho concentration is increased, pointing to the development of weak ferromagnetic moment, which is usually connected with uncompensated spins or spin canting. Hysteresis loops show the same fact, attaining higher magnetization with more Ho included, and becoming wider, i.e.magnetically harder.

Bismuth ferrite ; Multiferoics ; Magnetoelectric effect

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