| Autor: |
Dongshi Zhang, Wonsuk Choi, Yugo Oshima, Ulf Wiedwald, Sung-Hak Cho, Hsiu-Pen Lin, Yaw Kuen Li, Yoshihiro Ito, Koji Sugioka |
| Jazyk: |
angličtina |
| Rok vydání: |
2018 |
| Předmět: |
|
| Zdroj: |
Nanomaterials, Vol 8, Iss 8, p 631 (2018) |
| Druh dokumentu: |
article |
| ISSN: |
2079-4991 |
| DOI: |
10.3390/nano8080631 |
| Popis: |
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-Fe2O3 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-Fe2O3 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-Fe2O3 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. |
| Databáze: |
Directory of Open Access Journals |
| Externí odkaz: |
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