Structure Evolution and Spin-Glass Transition of Layered Compounds ALiFeSe2 (A = Na, K, Rb)

Duanduan Yuan; Ning Liu; Kunkun Li; Shifeng Jin; Jiangang Guo; Xiaolong Chen

doi:10.1021/acs.inorgchem.7b01937

Structure Evolution and Spin-Glass Transition of Layered Compounds ALiFeSe₂ (A = Na, K, Rb)

Inorg Chem. 2017 Nov 6;56(21):13187-13193. doi: 10.1021/acs.inorgchem.7b01937. Epub 2017 Oct 9.

Authors

Duanduan Yuan^{1

2}, Ning Liu^{1

2}, Kunkun Li^{1

2}, Shifeng Jin^{1

3}, Jiangang Guo¹, Xiaolong Chen^{1

3

4}

Affiliations

¹ Research & Development Center for Functional Crystals, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences , Beijing 100190, People's Republic of China.
² University of Chinese Academy of Sciences , Beijing 100049, People's Republic of China.
³ School of Physical Sciences, University of Chinese Academy of Sciences , Beijing 101408, People's Republic of China.
⁴ Collaborative Innovation Center of Quantum Matter , Beijing 100084, People's Republic of China.

PMID: 28991448
DOI: 10.1021/acs.inorgchem.7b01937

Abstract

Three new layered compounds, namely NaLiFeSe₂, KLiFeSe₂, and RbLiFeSe₂, have been discovered. NaLiFeSe₂ adopts a trigonal CaAl₂Si₂-type structure with space group P3̅m1, while the other two possess a tetragonal ThCr₂Si₂-type structure with space group I4/mmm. Structural refinements reveal that Li and Fe atoms randomly occupy the same sites in all these compounds without ordering. It is found that the radius of the alkali metals plays a vital role in determining the symmetry of this series of compounds. The substitution of Li at the Fe site shortens the layer spacing and elongates the A-Se bond length in the ThCr₂Si₂-type structure. The elongated Na-Se bond length would destabilize the ThCr₂Si₂-type structure in NaLiFeSe₂, suggesting that Na_xFe_2-ySe₂ lies at the border of ThCr₂Si₂-type and CaAl₂Si₂-type structures. Magnetic and resistivity measurements demonstrate that these compounds exhibit anisotropic spin-glass and narrow-band-gap semiconducting characteristics. First-principles calculations indicate that the introduction of Li enhances strong localization and weakens the correlation of the 3d electrons of Fe, which are responsible for the observed spin-glass transition and semiconducting conductions.