Coverage dependence of magnetic domain structure and magnetic anisotropy in supported Fe nanoparticles on Al2O3/NiAl (100)

Wen Chin Lin, C. B. Wu, P. J. Hsu, H. Y. Yen, Zheng Gai, Lan Gao, Jian Shen, Minn Tsong Lin

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Abstract

Studies of magnetic domain and magnetic anisotropy in collected nanoparticles are crucial for both understanding interparticle interaction and engineering in applications. In order to characterize the microscopic surface morphology and the nanoscale magnetic domain structure of Fe nanoparticles, a scanning tunneling microscope and a scanning electron microscope with polarization analysis (SEMPA) were used in our experiment. For the coverage of 9-13 monolayers (MLs) Fe deposited on Al2O3/NiAl (100), circular and well-separated nanoparticles were grown. As the coverage increased up to 23-33 ML, these Fe nanoparticles started to coalesce and form elongated islands. Therefore a transition from isotropic to anisotropic in-plane magnetism was observed. Our proposed uniaxial magnetic anisotropy models effectively explain the azimuthal angle dependent two-step hysteresis loops. Moreover, the in situ measured SEMPA images clearly show the coverage dependent evolution of magnetic domain structure. Variations in interparticle interaction and magnetic correlation length with increasing Fe coverage are also reported.

Original languageEnglish
Article number034312
JournalJournal of Applied Physics
Volume108
Issue number3
DOIs
StatePublished - Aug 1 2010

Funding

This work was supported by the National Science Council of Taiwan under Grant Nos. NSC 96-2120-M-002-011, NSC 95-2112-M-002-051-MY3, and NSC 96-2112-M-003-015-MY3. A portion of this research at Oak Ridge National Laboratory’s Center for Nanophase Materials Sciences was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy.

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