Magnetic Fe@FeOx, Fe@C and α-Fe2 O3 single-crystal nanoblends synthesized by femtosecond laser ablation of Fe in acetone

Dongshi Zhang, Wonsuk Choi, Yugo Oshima, Ulf Wiedwald, Sung Hak Cho, Hsiu Pen Lin, Yaw-Kuen Li, Yoshihiro Ito, Koji Sugioka*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

There are few reports on zero-field-cooled (ZFC) magnetization measurements for Fe@FeOx or FeOx particles synthesized by laser ablation in liquids (LAL) of Fe, and the minimum blocking temperature (TB) of 120 K reported so far is still much higher than those of their counterparts synthesized by chemical methods. In this work, the minimum blocking temperature was lowered to 52 K for 4–5 nm α-Fe2 O3 particles synthesized by femtosecond laser ablation of Fe in acetone. The effective magnetic anisotropy energy density (Keff) is calculated to be 2.7–5.4 × 105 J/m3, further extending the Keff values for smaller hematite particles synthesized by different methods. Large amorphous-Fe@α-Fe2 O3 and amorphous-Fe@C particles of 10–100 nm in diameter display a soft magnetic behavior with saturation magnetization (Ms) and coercivities (Hc) values of 72.5 emu/g and 160 Oe at 5 K and 61.9 emu/g and 70 Oe at 300 K, respectively, which mainly stem from the magnetism of amorphous Fe cores. Generally, the nanoparticles obtained by LAL are either amorphous or polycrystalline, seldom in a single-crystalline state. This work also demonstrates the possibility of synthesizing single-crystalline α-Fe2 O3 hematite crystals of several nanometers with (104), (113), (116) or (214) crystallographic orientations, which were produced simultaneously with other products including carbon encapsulated amorphous Fe (a-Fe@C) and Fe@FeOx core-shell particles by LAL in one step. Finally, the formation mechanisms for these nanomaterials are proposed and the key factors in series events of LAL are discussed.

Original languageEnglish
Article number631
JournalNanomaterials
Volume8
Issue number8
DOIs
StatePublished - 20 Aug 2018

Keywords

  • Blocking temperature
  • Core-shell
  • Femtosecond laser
  • Hematite α-Fe O
  • Laser ablation in liquids
  • Single-crystalline
  • Superparamagnetism

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