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Influence of La, Yb and Gd substitution on magnetic behaviour of bulk BiFeO3

Bismuth ferrite, BiFeO3 is perovskite multiferroic often studied because of its high ferroelectric and magnetic ordering temperatures, 1100 K and 630 K, respectively. Despite its room temperature multiferroicity, pure BiFeO3 is of limited technological importance, especially in bulk ceramic form, due to the antiferromagnetic state with very low net magnetic moment. Doping of BiFeO3 could disturb the antiferromagnetic order and induce magnetically ordered state with considerable magnetization coming from the uncompensated or canted spins. Therefore, magnetic behaviour of BiFeO3 doped with the heavy rare earth elements such as La, Yb and Gd, was investigated. Compounds of BiFeO3 in which 10% of Bi atoms are substituted with La, Yb and Gd were prepared using the hydro-evaporation synthesis. Magnetization of polycrystalline samples in powder form was investigated in a broad temperature range of 2-900 K. Splitting between the zero field cooled (ZFC) and field cooled (FC) magnetization curves indicate development of the weak ferromagnetism below the Néel temperature of around 610-640 K which is dependent on the composition. Magnetic hysteresis loops measured at the low temperature (5 K), room temperature, and high temperatures, just under and above transition temperature, also suggest the weak ferromagnetic behavior with relatively high coercive field. Complete magnetic results in full temperature range (2-900 K) clearly indicate enhancement of the weak ferromagnetism after performed substitution with rare earth elements La, Yb and Gd in bulk BiFeO3 ceramic. The authors acknowledge the financial support of the Croatian Science Foundation under the project UIP-2014-09-8276 and Ministry of Education and Science of Republic of Serbia (project number III45007), as well as program of bilateral scientific cooperation between Croatia and Serbia.

magnetic behaviour, magnetoelectric effect, multiferroics, bismuth ferrite

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