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arXiv 1005.3102cond-mat.mtrl-sci
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从晶体化学角度研究BiFeO3的磁电有序性

Magnetoelectric ordering of BiFeO3 from the perspective of crystal chemistry

L. M. Volkova, D. V. Marinin

摘要:

在本文中,我们研究的作用,晶体化学因素在创造条件形成磁电有序BiFeO 3。一般认为BiFeO_3铁电畸变的主要原因与Bi孤对电子的立体化学活性有关。然而,孤对电子在顺电正交β相中也是立体化学活性的。我们证明,在出现的金属-绝缘体,顺电-铁电和磁无序-有序类型的相变的关键作用属于孤对立体化学活性的程度的变化-它的连续增加,随着温度的降低。使用的结构数据,我们计算的符号和强度的磁耦合在BiFeO 3从945 C到25 C的范围内,发现的耦合,经历反铁磁-铁磁转变的温度降低,并引起反铁磁有序和它的延迟在温度方面,相比于铁电有序。讨论了空间调制自旋结构产生的原因以及La ~(3+)掺杂对空间调制自旋结构的抑制作用。

英文摘要:

In this paper we examine the role of crystal chemistry factors in creating conditions for formation of magnetoelectric ordering in BiFeO3. It is generally accepted that the main reason of the ferroelectric distortion in BiFeO3 is concerned with a stereochemical activity of the Bi lone pair. However, the lone pair is stereochemically active in the paraelectric orthorhombic beta-phase as well. We demonstrate that a crucial role in emerging of phase transitions of the metal-insulator, paraelectric-ferroelectric and magnetic disorder-order types belongs to the change of the degree of the lone pair stereochemical activity - its consecutive increase with the temperature decrease. Using the structural data, we calculated the sign and strength of magnetic couplings in BiFeO3 in the range from 945 C down to 25 C and found the couplings, which undergo the antiferromagnetic-ferromagnetic transition with the temperature decrease and give rise to the antiferromagnetic ordering and its delay in regard to temperature, as compared to the ferroelectric ordering. We discuss the reasons of emerging of the spatially modulated spin structure and its suppression by doping with La3+.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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