Magnetoresistance of oxygen concentration-modulated Co–Ti–O films

Masatoshi Nakano, Fuxing Wan, Jian Wang, Takumi Sannomiya, Shinji Muraishi, Takashi Harumoto, Yoshio Nakamura, Ji Shi

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Abstract

Co–Ti–O films have been prepared by a sputtering method in an Ar- and O2-mixed atmosphere. The O2 flow rate was modulated during the deposition to optimize the oxygen concentration and the microstructure of the films. For the as-deposited film, negligible magnetization and magnetoresistance (MR) were observed. The structure of the layers with lower O2 flow rate is basically amorphous alloy with Ti–O and Co–Ti bonds. On the other hand, in the layers with high O2 flow rate, both Ti and Co are oxidized. Upon thermal annealing in a vacuum, significant enhancements in both magnetization and MR in Co–Ti–O films were observed. It is found that granular structure of Co particles embedded in insulating TiO2 matrix is formed due to the oxygen diffusion and further oxidization of Ti as a result of the heat treatment. The significantly enhanced magnetization and MR ratio have been ascribed to the formation of nano-sized Co particles and the tunneling conduction between these Co particles across the TiO2 interlayers, respectively.

Original languageEnglish
Article number401
JournalApplied Physics A: Materials Science and Processing
Volume124
Issue number6
DOIs
Publication statusPublished - 2018 Jun 1
Externally publishedYes

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)

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    Nakano, M., Wan, F., Wang, J., Sannomiya, T., Muraishi, S., Harumoto, T., Nakamura, Y., & Shi, J. (2018). Magnetoresistance of oxygen concentration-modulated Co–Ti–O films. Applied Physics A: Materials Science and Processing, 124(6), [401]. https://doi.org/10.1007/s00339-018-1823-y