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首页> 外文期刊>RSC Advances >Substitution driven structural and magnetic transformation in Ca-doped BiFeO3 nanoparticles
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Substitution driven structural and magnetic transformation in Ca-doped BiFeO3 nanoparticles

机译：Ca掺杂BiFeO3纳米粒子的取代驱动结构和磁转变

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摘要

Bi1-xCaxFeO3; (x = 0-0.20) nanoparticles were synthesized by tartaric acid based sol-gel route. X-ray diffraction and electron microscopy studies reveal the phase purity and nanocrystalline nature (45-90 nm) of Bi1-xCaxFeO3 samples. The Ca ion substitution driven structural transition from rhombohedral (space group R3c) to orthorhombic (Pnma) symmetry leads to enhancement in saturation magnetization due to the distorted cycloid spin structure (as also suggested by Mossbauer studies) and uncompensated surface spins which is accorded with electron paramagnetic resonance (EPR) studies as well. The ferromagnetic ordering contribution increases up to x = 0.15 samples with maximum saturation magnetization of 0.09 emu g(-1) for x = 0.15 sample. The presence of high content orthorhombic phase for x = 0.20 sample results in the sharp decrease in the ferromagnetic component due to appearance of collinear antiferromagnetic ordering in agreement with EPR results. X-ray photoelectron spectroscopy confirmed the dominancy of Fe3+ oxidation states along with the shifting of the binding energy of Bi 4f orbital indicating the substitution of Ca2+ at Bi-site. Systematic change of Mossbauer parameters of nanoparticulate samples with Ca concentration are obtained by Mossbauer spectroscopy. The results of both one-and two-sextet fittings of the Mossbauer spectra provide evidence for destruction of the spin cycloid in Ca-doped BiFeO3 nanoparticles.
机译：Bi1-xCaxFeO3;通过基于酒石酸的溶胶-凝胶路线合成了（x = 0-0.20）纳米颗粒。 X射线衍射和电子显微镜研究揭示了Bi1-xCaxFeO3样品的相纯度和纳米晶体性质（45-90 nm）。 Ca离子取代驱动的结构从菱形（空间群R3c）到正交（Pnma）对称转变导致饱和磁化强度的增强，这是由于扭曲的摆线自旋结构（同样由Mossbauer研究表明）和与电子相符的未补偿的表面自旋顺磁共振（EPR）研究也是如此。铁磁有序贡献增加到x = 0.15个样品，对于x = 0.15个样品，最大饱和磁化强度为0.09 emu g（-1）。 x = 0.20样品中高含量的正交晶相的存在会导致铁磁成分的急剧下降，这是因为与EPR结果一致的共线反铁磁有序排列。 X射线光电子能谱证实了Fe3 +氧化态的优势以及Bi 4f轨道结合能的移动，表明在Bi位上Ca2 +被取代。通过Mossbauer光谱法获得了Ca浓度的纳米颗粒样品的Mossbauer参数的系统变化。 Mossbauer光谱的一次和两次延伸拟合的结果提供了破坏Ca掺杂BiFeO3纳米粒子中自旋摆线的证据。

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