Nanoscale measurement of giant saturation magnetization in α″-Fe 16 N 2 by electron energy-loss magnetic chiral dichroism

Xinfeng Chen, Soma Higashikozono, Keita Ito, Lei Jin, Ping Luen Ho, Chu Ping Yu, Nyan Hwa Tai, Joachim Mayer, Rafal E. Dunin-Borkowski, Takashi Suemasu, Xiaoyan Zhong

Research output: Contribution to journalArticlepeer-review

Abstract

Metastable α″-Fe 16 N 2 thin films were reported to have a giant saturation magnetization of above 2200 emu/cm 3 in 1972 and have been considered as candidates for next-generation rare-earth-free permanent magnetic materials. However, their magnetic properties have not been confirmed unequivocally. As a result of the limited spatial resolution of most magnetic characterization techniques, it is challenging to measure the saturation magnetization of the α″-Fe 16 N 2 phase, as it is often mixed with the parent α′-Fe 8 N phase in thin films. Here, we use electron energy-loss magnetic chiral dichroism (EMCD), aberration-corrected transmission electron microscopy, X-ray diffraction and macroscopic magnetic measurements to study α″-Fe 16 N 2 (containing ordered N atoms) and α′-Fe 8 N (containing disordered N atoms). The ratio of saturation magnetization in α″-Fe 16 N 2 to that in α′-Fe 8 N is determined to be 1.31 ± 0.10 from quantitative EMCD measurements and dynamical diffraction calculations, confirming the giant saturation magnetization of α″-Fe 16 N 2 . Crystallographic information is also obtained about the two phases, which are mixed on the nanoscale.

Original languageEnglish
Pages (from-to)37-43
Number of pages7
JournalUltramicroscopy
Volume203
DOIs
Publication statusPublished - 2019 Aug
Externally publishedYes

Keywords

  • Electron energy-loss magnetic chiral dichroism
  • Giant saturation magnetization
  • Rare-earth-free permanent magnetic materials
  • α″-Fe N , high spatial resolution

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Instrumentation

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