物理学报2017，Vol.66Issue(18)：173-179,7.DOI:10.7498/aps.66.186102
单晶CeB6发射性能及磁电阻各向异性研究
Anisotropy study on thermionic emission and magnetoresistivity of single crystal CeB6
摘要
Abstract
Cerium hexaboride (CeB6) as a heavy fermion compound displays a number of interesting low-temperature physical properties such as dense Kondo behavior and a complex magnetic phase diagram due to the interaction between itinerant and local electrons.Recently,the electron emission property of CeB6 has received much attention because it has potential applications in replacing the commercial LaB6 cathode and serving as new-generation thermal cathodes.In addition,by comparison with other metal cathodes,it also possesses some advantages,such as a low work function,low volatility,high brightness,thermal stability and high mechanical strength.However,so far the thermionic emission properties of CeB6 single crystal surfaces except for the (100) surfaces have been rarely reported.Whether the different crystal surfaces of CeB6 contribute to the various interesting emission properties is main research purpose of the present work.In this paper,the (110),(111),(210) and (310) crystal surfaces of single crystal CeB6 are determined by the X-ray Laue diffraction method,and their thermionic emission current densities are measured at different temperatures and applied voltages.As a result,the maximum emission current densities of the (110),(111),(210) and (310) crystal surfaces at 1873 K are 38.4,11.54,50.4 and 20.8 A/cm2,respectively.When their cathode temperatures are all 1773 K,their maximum emission current densities are 15.2,5.43,28.0 and 11.44 A/cm2.In addition,when the cathode temperature decreases to 1673 K,their maximum emission current densities are 4.24,0.9,6.2 and 2.43 A/cm2.It means that the thermionic emissions are strongly anisotropic for the different crystal surfaces.In general,the maximum emission current density of (100) crystal surface of LaB6 single crystal is about 10 A/cm2 at 1700 K.By comparing the emission current density of CeB6 single crystal at 1773 K with that of LaB6 at 1700 K,it is found that the emission properties of (210) crystal surface are maybe close to those of LaB6.The work function values of the (110),(111),(210) crystal surfaces calculated by the Richardson-Dushman formula are 2.64,2.71 and 2.40 eV,respectively.Among these,the (210) crystal surface possesses the smallest value of the work function,which is hopeful for being used as an electron source of scanning electron microscopy.Zero-field magnetoresistivity measurments confirm the transition temperatures of TQ =3.3 K and TN =2.4 K.Field-angle dependent magnetoresistivity measurments show that the electrical resistivity varies between 69 μΩ·cm and 73 μΩ.cm when the crystal rotates from the [001] to the [011] direction.This indicates that the electrical resistivity in a magnetic field is also anisotropic.关键词
CeB6/逸出功/磁电阻Key words
CeB6/work function/magnetoresistance引用本文复制引用
包黎红,陶如玉,特古斯,黄颖楷,冷华倩,Anne de Visser..单晶CeB6发射性能及磁电阻各向异性研究[J].物理学报,2017,66(18):173-179,7.基金项目
国家自然科学基金(批准号:51662034)和内蒙古自治区高等学校“青年科技英才支持计划”(批准号:NJYT-14-B03)资助的课题.Project supported by the National Natural Science Foundation of China (Grant No.51662034) and the Program for Young Talents of Science and Technology in Universities of Inner Mongolia,China (Grant No.NJYT-14-B03). （批准号:51662034）
