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-GdAHG) exhibit a magnetic compensation at room temperature. The Bi-GdAIIG nanoparticles were made using coprecipitation and heat-treatment processes. The magnetic profiles of the Bi-GdAlIG (BiGd{sub}2Al{sub}xFe{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}2Al{sub}0.7Fe{sub}4.3O{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}2Al{sub}0.5Fe{sub}4.5O{sub}12 nanoparticles was estimated 55 nm by Scherrer's equation, and observed to be about 100 nm by scanning electron microscope image.
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