Sazonov Andrew, Hutanu Vladimir, Meven Martin, Roth Georg, Kézsmárki István, Murakawa Hiroshi, Tokura Yoshinori, Náfrádi Bálint
Institute of Crystallography, RWTH Aachen University, Aachen, Germany.
Department of Physics, Budapest University of Technology and MTA-BME Lendület Magneto-optical Spectroscopy Research Group, Budapest, Hungary.
Acta Crystallogr B Struct Sci Cryst Eng Mater. 2016 Feb;72(Pt 1):126-32. doi: 10.1107/S2052520615023057. Epub 2016 Jan 29.
In the antiferromagnetic ground state, below TN ≃ 5.7 K, Ca2CoSi2O7 exhibits strong magnetoelectric coupling. For a symmetry-consistent theoretical description of this multiferroic phase, precise knowledge of its crystal structure is a prerequisite. Here we report the results of single-crystal neutron diffraction on Ca2CoSi2O7 at temperatures between 10 and 250 K. The low-temperature structure at 10 K was refined assuming twinning in the orthorhombic space group P2(1)2(1)2 with a 3 × 3 × 1 supercell [a = 23.52 (1), b = 23.52 (1), c = 5.030 (3) Å] compared with the high-temperature normal state [tetragonal space group P42(1)m, a = b ≃ 7.86, c ≃ 5.03 Å]. The precise structural parameters of Ca2CoSi2O7 at 10 K are presented and compared with the literature X-ray diffraction results at 130 and 170 K (low-temperature commensurate phase), as well as at ∼ 500 K (high-temperature normal phase).
在反铁磁基态下，低于居里温度TN≃5.7 K时，Ca2CoSi2O7表现出强磁电耦合。对于这个多铁性相的对称一致理论描述，精确了解其晶体结构是一个先决条件。在此，我们报告了在10至250 K温度范围内对Ca2CoSi2O7进行的单晶中子衍射结果。假设在正交空间群P2(1)2(1)2中存在孪晶，采用3×3×1超晶胞 [a = 23.52 (1)，b = 23.52 (1)，c = 5.030 (3) Å] 对10 K时的低温结构进行了精修，与高温正常态 [四方空间群P42(1)m，a = b ≃ 7.86，c ≃ 5.03 Å] 进行对比。给出了10 K时Ca2CoSi2O7的精确结构参数，并与文献中130和170 K（低温相称相）以及约500 K（高温正常相）时的X射线衍射结果进行了比较。
