The effects of oxygen in spinel oxide Li1+xTi2-xO4-δ thin films

Yanli Jia; Ge He; Wei Hu; Hua Yang; Zhenzhong Yang; Heshan Yu; Qinghua Zhang; Jinan Shi; Zefeng Lin; Jie Yuan; Beiyi Zhu; Lin Gu; Hong Li; Kui Jin

doi:10.1038/s41598-018-22393-8

The effects of oxygen in spinel oxide Li_1+xTi_2-xO_4-δ thin films

Sci Rep. 2018 Mar 5;8(1):3995. doi: 10.1038/s41598-018-22393-8.

Authors

Yanli Jia^{1

2}, Ge He^{1

2}, Wei Hu^{1

2}, Hua Yang^{1

2}, Zhenzhong Yang^{1

2}, Heshan Yu^{1

2}, Qinghua Zhang^{1

2}, Jinan Shi^{1

2}, Zefeng Lin^{1

2}, Jie Yuan^{1

2}, Beiyi Zhu^{1

2}, Lin Gu^{1

2

3}, Hong Li^{1

2

3}, Kui Jin^{4

5

6}

Affiliations

¹ Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.
² School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China.
³ Collaborative Innovation Center of Quantum Matter, Beijing, 100190, China.
⁴ Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China. kuijin@iphy.ac.cn.
⁵ School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China. kuijin@iphy.ac.cn.
⁶ Collaborative Innovation Center of Quantum Matter, Beijing, 100190, China. kuijin@iphy.ac.cn.

Abstract

The evolution from superconducting LiTi₂O_4-δ to insulating Li₄Ti₅O₁₂ thin films has been studied by precisely tuning the oxygen pressure in the sample fabrication process. In superconducting LiTi₂O_4-δ films, with the increase of oxygen pressure, the oxygen vacancies are filled gradually and the c-axis lattice constant decreases. When the oxygen pressure increases to a certain critical value, the c-axis lattice constant becomes stable, which implies that the sample has been completely converted to Li₄Ti₅O₁₂ phase. The two processes can be manifested by the angular bright-field images of the scanning transmission electron microscopy techniques. The transition temperature (T _ch ) of magnetoresistance from the positive to the negative shows a nonmonotonic behavior, i.e. first decrease and then increase, with the increase of oxygen pressure. We suggest that the decrease T_ch can be attributed to the suppressing of orbital-related state, and the inhomogeneous phase separated regions contribute positive MR and thereby lead to the reverse relation between T_ch and oxygen pressure.