Magnetic Orientation of Chemically Partially Ordered FePt Nanoparticles by Annealing in Magnetic Field

概要

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We have investigated a method of magnetically orienting FePt nanoparticles. Uniaxial magnetic crystals such as chemically ordered FePt can be oriented by an external magnetic field. We therefore attempted to prepare colloidal chemically ordered FePt nanoparticles, using a surface reduction and heat treatment. The heat treatment changed the crystal structure of the nanoparticles from disordered to partially ordered, sustaining the colloidal status. A film of the partially ordered nanoparticles was then annealed in a magnetic field. As a result, the annealed film became magnetically anisotropic; that is, both coercivity and magnetic squareness along the direction of the applied field during annealing were ${>}30$% larger than those along the perpendicular direction. Although the observed magnetic anisotropy differed from the ideal, we analyzed the resultant magnetic orientation status by applying switching field distributions (SFDs). The analysis implied that annealing in a magnetic field has great potential for orienting uniaxial magnetic nanoparticles.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2006-08-15