Nanostructured antiferromagnetic (AFM) NiO has attracted much attention from both the fundamental and applied perspectives. Understanding the two-magnon (2 M) is of great significance in NiO applications such as spin valves and next-generation magnetic random access memories (MRAM). We investigated the phonon modes and antiferromagnetically ordered states of NiO nanoparticles prepared by empirically controlled measurements. An intensity enhancement of the 2 M mode was observed by Raman spectroscopy as the NiO nanoparticles were vacuum annealed at 650 ℃. The increased 2 M peak intensity in NiO nanoparticles is explained by the local symmetry conversions from NiO5 to NiO6 configurations due to the oxygen redistribution during the vacuum annealing. The change of the splitting of anisotropic transverse optical (TO) phonon with different oxygen contents was also revealed by the Raman spectroscopy. We have shown that the changes in the oxygen environment underlie both the change in the 2 M intensity and the splitting of TO phonon in the NiO nanoparticles. Our work offers an efficient avenue to strengthen the AFM ordering and emphasizes the effect of vacuum annealing of the NiO nanoparticles, opening the interesting possibility of individual parameter control in practical applications.
|Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy
|Published - 5 Sep 2023
Bibliographical noteFunding Information:
The measurements in this work were supported by Korea Basic Science Institute (National Research Facilities and Equipment Center) grant funded by the Ministry of Education (2020R 1A 6C 101B194). I.S.Y. acknowledges the financial support by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2021R1A6A1A10039823). S.J.K. acknowledges the financial support by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (NRF-2021R1A2C2091348).
© 2023 Elsevier B.V.
- NiO nanoparticles
- Oxygen content
- Raman spectroscopy
- Transverse optical phonon mode
- Two-magnon mode
- Vacuum annealing