Structural and magnetic phase transitions in Eu1-xLaxFe3(BO3)4 (x = 0, 0.18).

IF 1.3 3区 化学 Q3 CHEMISTRY, MULTIDISCIPLINARY
Ekaterina S Smirnova, Kirill V Frolov, Ekaterina V Sidorova, Timofei A Sorokin, Olga A Alekseeva, Anton V Guskov, Pavel G Gagarin, Irina A Gudim
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引用次数: 0

Abstract

The crystal structures and hyperfine magnetic parameters of EuFe3(BO3)4 and mixed Eu0.82La0.18Fe3(BO3)4 were studied over a wide temperature range in order to analyze correlations of the structural and magnetic features and the phase transitions in multiferroic compounds of the rare-earth iron borate family. The chemical compositions of the crystals are reported from X-ray fluorescence analysis. The crystal structures of EuFe3(BO3)4 and Eu0.82La0.18Fe3(BO3)4 were determined using single-crystal X-ray diffraction in the temperature range 25-500 K. A structural phase transition is observed in EuFe3(BO3)4 below 89 K which is related to distortions in the interatomic distances and angles. The most significant of which are for R-O, R-B, R-Fe, Fe-O and Fe-Fe distances, and the angles between the BO3 triangles and the ab plane. There is no structural phase transition in lanthanum-doped EuFe3(BO3)4 based on specific heat measurements (2.2-101.3 K) and structure analysis (25-500 K), and the temperature dependences of the interatomic distances and angles are smooth. The lengths of the superexchange paths needed for the appearance of a structural phase transition in RFe3(BO3)4 have been proposed. Negative thermal expansion is observed for both compounds below 90 K, resulting from a growth of the interatomic Fe-Fe distances in the iron chains during cooling. The largest atomic displacement parameters are observed for O atoms (O2), indicating that they have the highest mobility. The magnetic properties of EuFe3(BO3)4 and Eu0.82La0.18Fe3(BO3)4 were analyzed using Mössbauer spectroscopy in the temperature range 4.5-298 K. Néel temperatures (TN) of 34.57 (1) and 32.22 (1) K are obtained based on Mössbauer spectroscopy for the pure and doped crystals, respectively. The maximum specific heat capacity temperature dependence related to the magnetic phase transition for the doped crystal is observed at 31.2 K. A violation of the strict arrangement of antiferromagnetic ordering in the ab plane in the La-doped crystals at low temperatures is suggested. The magnetic contributions of the two structural positions of the iron ions to the Mössbauer spectra could not be distinguished in either pure and doped compounds, regardless of whether they are in the paramagnetic and antiferromagnetic regions.

Eu1-xLaxFe3(BO3)4的结构相变和磁相变(x = 0,0.18)。
在较宽的温度范围内研究了EuFe3(BO3)4和混合Eu0.82La0.18Fe3(BO3)4的晶体结构和超细磁性参数,以分析稀土硼酸铁族多铁化合物的结构和磁性特征与相变的相关性。用x射线荧光分析报告了晶体的化学成分。在25 ~ 500 K的温度范围内,用单晶x射线衍射测定了EuFe3(BO3)4和Eu0.82La0.18Fe3(BO3)4的晶体结构。在89 K以下,EuFe3(BO3)4发生了结构相变,这与原子间距离和角度的畸变有关。其中最重要的是R-O、R-B、R-Fe、Fe-O和Fe-Fe之间的距离,以及BO3三角形与ab平面之间的夹角。基于比热测量(2.2 ~ 101.3 K)和结构分析(25 ~ 500 K),镧掺杂EuFe3(BO3)4没有发生结构相变,原子间距离和原子间角的温度依赖性较好。提出了RFe3(BO3)4中出现结构相变所需的超交换路径长度。两种化合物在低于90k时均观察到负热膨胀,这是由于冷却过程中铁链中Fe-Fe原子间距离的增加。O原子(O2)的原子位移参数最大,表明它们具有最高的迁移率。利用Mössbauer光谱分析了EuFe3(BO3)4和Eu0.82La0.18Fe3(BO3)4在4.5 ~ 298 K范围内的磁性能。通过Mössbauer光谱分析得到纯晶体和掺杂晶体的n温度(TN)分别为34.57(1)和32.22 (1)K。在31.2 K时观察到掺杂晶体与磁相变相关的最大比热容温度依赖性。在低温下,la掺杂晶体在ab平面上违反了严格的反铁磁有序排列。铁离子的两个结构位置对Mössbauer光谱的磁贡献在纯化合物和掺杂化合物中都无法区分,无论它们是在顺磁区还是反铁磁区。
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来源期刊
Acta crystallographica Section B, Structural science, crystal engineering and materials
Acta crystallographica Section B, Structural science, crystal engineering and materials CHEMISTRY, MULTIDISCIPLINARYCRYSTALLOGRAPH-CRYSTALLOGRAPHY
CiteScore
3.60
自引率
5.30%
发文量
0
期刊介绍: Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials publishes scientific articles related to the structural science of compounds and materials in the widest sense. Knowledge of the arrangements of atoms, including their temporal variations and dependencies on temperature and pressure, is often the key to understanding physical and chemical phenomena and is crucial for the design of new materials and supramolecular devices. Acta Crystallographica B is the forum for the publication of such contributions. Scientific developments based on experimental studies as well as those based on theoretical approaches, including crystal-structure prediction, structure-property relations and the use of databases of crystal structures, are published.
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