三方Cr_(5)Te_(8)的磁结构和反常热膨胀  

Magnetic Structure and Abnormal Thermal Expansion of Trigonal Cr_(5)Te_(8)

作　　者：任卫军[1,2] 安萌 高飞 罗小华 李昺[1,2] 张志东 王进威[3] REN Weijun;AN Meng;GAO Fei;LUO Xiaohua;LI Bing;ZHANG Zhidong;WANG Chin-Wei(Shenyang National Laboratory for Materials Science,Institute of Metal Research,Chinese Academy of Sciences,Shenyang 110016,China;School of Materials Science and Engineering,University of Science and Technology of China,Shenyang 110016,China;Australian Nuclear Science and Technology Organisation,New Illawarra Road,Lucas Heights,NSW 2234,Australia)

机构地区：[1]中国科学院金属研究所沈阳材料科学国家研究中心,沈阳110016 [2]中国科学技术大学材料科学与工程学院,沈阳110016 [3]Australian Nuclear Science and Technology Organisation,New Illawarra Road,Lucas Heights,NSW 2234,Australia

出　　处：《金属学报》2024年第8期1150-1154,共5页Acta Metallurgica Sinica

基　　金：国家重点研发计划项目No.2020YFA0406002;国家自然科学基金面上项目No.52071323。

摘　　要：很多二元Cr-Te化合物具有NiAs结构,其中金属Cr原子出现不同程度的有序缺位。Cr_(5)Te_(8)有三方和单斜2种结构,本工作采用粉末X射线和中子衍射结合Rietveld全谱拟合,确定了用自助溶剂生长的三方Cr_(5)Te_(8)单晶具有P3m1晶体结构,点阵参数a=0.3900 nm,c=0.5986 nm。粉末中子衍射实验揭示Cr_(5)Te_(8)是磁矩沿c方向的共线铁磁化合物,a方向具有小的负热膨胀,c方向显示正常热膨胀。以最低温3.3 K为参考温度点,在3.3~300 K温度范围内,a方向平均热膨胀系数为-10.7×10^(-6)K^(-1),c方向平均膨胀系数为52.4×10^(-6)K^(-1)。[101]、[302]和[201]取向的Cr_(5)Te_(8)具有近零热膨胀,具备应用前景。Cr_(5)Te_(8)的反常热膨胀与其磁有序没有明显关联,可能与晶格中存在大量的Cr空位有关。Many binary Cr-Te compounds can be regarded as formed due to varying degrees of ordered vacancies of metal Cr atoms in Cr-Te with the NiAs structure.Among them,Cr_(5)Te_(8) shows two structures:trigonal and monoclinic.This study determined that Cr_(5)Te_(8) grown using the self-flux method shows a trigonal P3m1 crystal structure with lattice constants a=0.3900 nm and c=0.5986 nm,as elucidated through the Rietveld refinement of powder X-ray and neutron diffraction patterns.Neutron powder diffraction experiments reveal its collinear ferromagnetic compound,with Cr magnetic moments oriented along the c axis.In addition,it exhibits low negative thermal expansion along the a direction and normal thermal ex pansion along the c direction.Within the temperature range of 3.3-300 K,using the lowest temperature of 3.3 K as a reference,the average thermal expansion coefficient of Cr_(5)Te_(8) is−10.7×10^(-6) and 52.4×10^(-6)K^(-1) in the a and c directions,respectively.Cr_(5)Te_(8) crystals oriented along the[101],[302],and[201]directions show near-zero thermal expansion and thus have wide application prospects.The abnormal thermal expansion of Cr_(5)Te_(8) is apparently unrelated to its magnetic order but may be related to the Cr vacancies in the crystal lattice.

关 键 词：粉末中子衍射 负热膨胀 磁结构 

分 类 号：O482.54[一般工业技术—材料科学与工程]