Open AccessDependence of exchange anisotropy and coercivity on the Fe–oxide structure in oxygen-passivated Fe nanoparticles
Author(s) -
C. Prados,
M. Multigner,
A. Hernando,
J.C. Sánchez,
A. Fernández,
C.F. Conde,
A. Conde
Publication year - 1999
Publication title -
journal of applied physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.699
H-Index - 319
eISSN - 1089-7550
pISSN - 0021-8979
DOI - 10.1063/1.370280
Subject(s) - coercivity , materials science , exchange bias , amorphous solid , ferromagnetism , magnetic anisotropy , transmission electron microscopy , oxide , magnetization , magnetic hysteresis , crystallization , nanoparticle , antiferromagnetism , analytical chemistry (journal) , condensed matter physics , chemical engineering , chemistry , crystallography , metallurgy , nanotechnology , magnetic field , physics , quantum mechanics , engineering , chromatography
Ultrafine Fe particles have been prepared by the inert gas condensation method and subsequently oxygen passivated. The as-obtained particles consist in an Fe core surrounded by an amorphous Fe-oxide surface layer. The antiferromagnetic character of the Fe-oxide surface induces an exchange anisotropy in the ferromagnetic Fe core when the system is field cooled. Samples have been heat treated in vacuum at different temperatures. Structural changes of the Fe–O layer have been monitored by x-ray diffraction and transmission electron microscopy. Magnetic properties as coercivity, hysteresis loop shift, and evolution of magnetization with temperature have been analyzed for different oxide crystallization stages. A decrease of the exchange anisotropy strength is reported as the structural disorder of the surface oxide layer is decreased with thermal treatment
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