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All-Magnetic Slabs and Multiferroism in (Bi2–xO2)(MF4) Aurivillius Oxyfluorides (M = Fe and Ni)
Chemistry of Materials ( IF 7.2 ) Pub Date : 2022-06-09 , DOI: 10.1021/acs.chemmater.2c01213
Olivier Mentré 1 , Miguel A. Juárez-Rosete 1 , Marie Colmont 1 , Clemens Ritter 2 , François Fauth 3 , Mathieu Duttine 4 , Marielle Huvé 1 , Christine Terryn 5 , Victor Duffort 1 , Ángel M. Arévalo-López 1
Affiliation  

The Aurivillius-layered compounds with a predominant fraction of paramagnetic transition metals are an emerging playground for the discovery of magnetoelectric or multiferroic compounds. This aim was recently achieved by incorporating F anions in the perovskite layer of the (Bi2O2)(CoF4) compound, only described so far in a disordered model (unit cell: ap, ap, c). Here, we report the investigation on the representative compounds (Bi2O2)(MF4) (M = Fe and Ni) using single crystal, synchrotron, neutron, and electron diffraction. These reveal that the crystallographic average cell (√2 × ap, √2 × ap, c) is orthorhombic, polar, and accompanied by versatile (in)commensurate modulations. The supercell model was fully refined for (Bi2–xO2)(FeF4) [q = (0, 1/2, 0)] in the P2111 polar space group with transverse Fe-displacements relative to q. Bi deficiency is compensated by a mixed Fe∼2.5+ valence, but the ideal stoichiometry is preserved for (Bi2O2)(NiF4). Both compounds are antiferromagnetic below TN = 89 K (Fe) and 45 K (Ni), with moments lying in the (ac) plane and a weak ferromagnetic component along the b-axis. Density functional theory calculations validate a strongly anisotropic distribution of magnetic exchanges (Jab/Jc > 10). A broad anomaly on the dielectric constant at TN and a polarization loop at room temperature were obtained on (Bi2–xO2)(FeF4) single crystals, revealing multiferroism with magnetoelectric couplings.

中文翻译:

(Bi2–xO2)(MF4) Aurivillius Oxyfluorides (M = Fe 和 Ni) 中的全磁板和多铁性

具有主要部分顺磁性过渡金属的Aurivillius层状化合物是发现磁电或多铁化合物的新兴领域。最近通过在 (Bi 2 O 2 )(CoF 4 ) 化合物的钙钛矿层中加入 F -阴离子来实现这一目标,迄今为止仅在无序模型(晶胞:a pa pc)中进行了描述。在这里,我们报告了对代表性化合物(Bi 2 O 2)(M F 4)(M= Fe 和 Ni) 使用单晶、同步加速器、中子和电子衍射。这些揭示了晶体学平均晶胞 (√2 × a p , √2 × a p , c ) 是正交的、极性的,并伴随着通用的(不)相称的调制。对于P 2 1 11 极性空间群中的 (Bi 2– x O 2 )(FeF 4 ) [ q = (0, 1/2, 0)] ,超级胞模型得到了充分的改进,具有相对于q的横向 Fe 位移。Bi 缺乏被混合的 Fe ∼2.5+价补偿,但理想的化学计量比(Bi 2O 2 )(NiF 4 )。两种化合物在T N = 89 K (Fe) 和 45 K (Ni) 以下都是反铁磁性的,其矩位于 ( ac ) 平面内,沿b轴具有弱铁磁分量。密度泛函理论计算验证了磁交换的强各向异性分布 ( J ab / J c > 10)。在 (Bi 2– x O 2 )(FeF 4 ) 单晶上获得了T N处介电常数的广泛异常和室温下的极化回路,揭示了具有磁电耦合的多铁性。
更新日期:2022-06-09
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