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Tunable Cobalt Vacancies and Related Properties in LaCoxAs2



Shijie Shen, Gang Wang, Shifeng Jin, Qingzhen Huang, Tianping Ying, Dandan Li, Xiaofang Lai, Tingting Zhou, Han Zhang, Zhiping Lin, Xiaozhi Wu, Xiaolong Chen


The origin of transition metal vacancies and their effects on the properties of ThCr2Si2-type compounds have been less studied and poorly understood. Here we carefully investigate the structure, physical properties, and electronic structure for a series of lanthanum cobalt arsenides with nominal composition of LaCoxAs2 (1.6 ¿ x ¿ 2.1). It is revealed that the occupancy of Co can be tuned between 1.98(1) and 1.61(1). The structural analyses based on x-ray and neutron diffractions show that the existence of Co vacancies results from overmuch electrons due to the formation of covalent bond between As-As. Such interlayer anion-anion bonding offers an alternative charge compensation mechanism to allow for the introduction of vacancies. These Co vacancies affect the magnetic and electrical properties greatly, adjusting the Curie temperature from 205 K to 47 K and increasing the resistivity by more than 100%. First-principles calculations indicate that the Co vacancies weaken the spin polarization and reduce the density of states at the Fermi level, resulting in decreased Curie temperature and increased resistivity, respectively. Our results address the importance of transition metal vacancies in ThCr2Si2-type structure and offer a reliable route to tune the magnetism of ThCr2Si2-type structure.
Chemistry of Materials


Superconductor, XRD & NPD structure, Itinerant ferromagnetic


Shen, S. , Wang, G. , Jin, S. , Huang, Q. , Ying, T. , Li, D. , Lai, X. , Zhou, T. , Zhang, H. , Lin, Z. , Wu, X. and Chen, X. (2014), Tunable Cobalt Vacancies and Related Properties in LaCo<sub>x</sub>As<sub>2</sub>, Chemistry of Materials, [online], (Accessed April 20, 2024)
Created October 20, 2014, Updated October 12, 2021