TY - JOUR
T1 - Tunable K vacancies in K1− xCo2Se2 and their effects on structure and ferromagnetism
AU - Guo, Zhongnan
AU - Yan, Xiaoxiao
AU - Zheng, Lirong
AU - Han, Xue
AU - Wu, Dan
AU - Liu, Ning
AU - Sun, Fan
AU - Wang, Da
AU - Yuan, Wenxia
N1 - Publisher Copyright:
© 2019
PY - 2019/11/15
Y1 - 2019/11/15
N2 - Deeply understanding the role of intermediate metal A on structure and related properties of ThCr2Si2-type transition metal compounds ATM2X2 is of great importance for designing novel layered functional materials. However, inducing A vacancies usually trends to destroy the original structure in reported systems so far, which hampers the further research. Here we report the controllable K vacancies in K1− xCo2Se2 system (0 ≤ x ≤ 0.3), where both the ThCr2Si2-type structure and intact tetrahedral [CoSe] layers can be maintained with the varying occupancies of K. By inducing K vacancies in structure, tetragonality of the lattice for K1− xCo2Se2 increases with the shortened a and elongated c. The (CoSe4) tetrahedron is also compressed perpendicular to the c direction resulted from the K deficiency. X-ray absorption near-edge structure reveals that the valence state of Co is basically unaffected by K deficient with the absorption edge of Co K-edge unchanged. Concerning the physical properties, K vacancies increase the resistivity of metallic K1− xCo2Se2 due to the decreased charge transfer from K+ to [CoSe] layers. More importantly, the ferromagnetic interaction of K1− xCo2Se2 is unexpectedly weakened by raising K vacancies with the Curie temperature shifted from 80 to 52 K, despite the shortened Co-Co distance. First-principles calculation reveals that the spin polarization is weakened resulted from the K vacancies, mainly attributed to the reduced charge transfer from K+ to [CoSe] host. Our results clearly indicate the domination of transferred electrons from intermediate metal A on the magnetic interaction of ATM2X2, and also show the feasibility to regulate the structure and related properties of ATM2X2 by controlling the A content.
AB - Deeply understanding the role of intermediate metal A on structure and related properties of ThCr2Si2-type transition metal compounds ATM2X2 is of great importance for designing novel layered functional materials. However, inducing A vacancies usually trends to destroy the original structure in reported systems so far, which hampers the further research. Here we report the controllable K vacancies in K1− xCo2Se2 system (0 ≤ x ≤ 0.3), where both the ThCr2Si2-type structure and intact tetrahedral [CoSe] layers can be maintained with the varying occupancies of K. By inducing K vacancies in structure, tetragonality of the lattice for K1− xCo2Se2 increases with the shortened a and elongated c. The (CoSe4) tetrahedron is also compressed perpendicular to the c direction resulted from the K deficiency. X-ray absorption near-edge structure reveals that the valence state of Co is basically unaffected by K deficient with the absorption edge of Co K-edge unchanged. Concerning the physical properties, K vacancies increase the resistivity of metallic K1− xCo2Se2 due to the decreased charge transfer from K+ to [CoSe] layers. More importantly, the ferromagnetic interaction of K1− xCo2Se2 is unexpectedly weakened by raising K vacancies with the Curie temperature shifted from 80 to 52 K, despite the shortened Co-Co distance. First-principles calculation reveals that the spin polarization is weakened resulted from the K vacancies, mainly attributed to the reduced charge transfer from K+ to [CoSe] host. Our results clearly indicate the domination of transferred electrons from intermediate metal A on the magnetic interaction of ATM2X2, and also show the feasibility to regulate the structure and related properties of ATM2X2 by controlling the A content.
KW - Ferromagnetism
KW - K vacancies
KW - KCoSe
KW - ThCrSi-type structure
UR - http://www.scopus.com/inward/record.url?scp=85067690342&partnerID=8YFLogxK
U2 - 10.1016/j.jmmm.2019.165473
DO - 10.1016/j.jmmm.2019.165473
M3 - Article
AN - SCOPUS:85067690342
SN - 0304-8853
VL - 490
JO - Journal of Magnetism and Magnetic Materials
JF - Journal of Magnetism and Magnetic Materials
M1 - 165473
ER -