Crystal growth, structure, and superconducting properties of the beta-pyrochlore KOs2O6статья
Статья опубликована в высокорейтинговом журнале
Информация о цитировании статьи получена из
Web of Science,
Scopus
Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:Single crystals of KOs2O6 have been grown in a sealed quartz ampoule. Detailed single crystal x-ray diffraction studies at room temperature show Bragg peaks that violate Fd (3) over barm symmetry. With a comparative structure refinement the structure is identified as noncentrosymmetric (Fd (3) over barm). Compared to the ideal beta-pyrochlore lattice (Fd (3) over barm), both Os tetrahedral and O octahedral networks exhibit breathing mode like volume changes accompanied by strong anisotropic character of the K channels. The crystals show metallic conductivity and a sharp transition to the superconducting state at T-c=9.65 K. Superconducting properties have been investigated by magnetization measurements performed in a temperature range from 2 to 12 K and in magnetic fields from 0 to 60 kOe. The temperature dependence of the upper critical field H-c2(T) has been determined and the initial slope (dH(c2)/dT)(Tc)=-33.3 kOe/K has been obtained near T-c. The upper critical field at zero temperature was estimated to be H-c2(0)congruent to 230 kOe, which is a value close to the Pauli paramagnetic limiting field H-p(0)congruent to 250 kOe. Then, the Ginzburg-Landau (GL) coherence length xi(GL)(0)approximate to 3.8 nm was calculated, and the Maki parameter alpha approximate to root 2 was obtained, suggesting the possibility that KOs2O6 might behave unconventionally at low temperatures and high magnetic fields.