Enhanced coercive-force of Al-substituted Bi-GdIG nanoparticles with magnetic compensation composition

In garnet particles, higher coercive-force is required to develop a practical magneto-optical storage media. Therefore we in this article develop high coercive-force particles reflecting the magnetic compensation induced by the aluminum substitution for applying the garnet particles to magneto-optical storage media. Nanoparticles of aluminum substituted bismuth gadolinium iron garnet (Bi-GdAlIG) exhibit a magnetic compensation at room temperature. The Bi-GdAlIG nanoparticles were made using coprecipitation and heattreatment processes. The magnetic profiles of the Bi-GdAlIG (BiGd/sub 2/Al/sub x/Fe/sub 5-x/O/sub 12/; 0 < x < 1.2) nanoparticles shows shallow minima at x=0.7 reflecting the magnetic compensation induced by the aluminum substitution. The coercive-force also peaks at x=0.7, which can be consistently explained by the magnetic compensation. The BiGd/sub 2/Al/sub 0.7/Fe/sub 4.3/O/sub 12/ nanoparticles demonstrate the enhanced coercivity of 320 Oe, which is factor of 2 larger than the x=0. The average size of the BiGd/sub 2/Al/sub 0.5/Fe/sub 4.5/O/sub 12/ nanoparticles was estimated 55 nm by Scherrerʹs equation, and observed to be about 100 nm by scanning electron microscope image.