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 heat-treatment processes. The magnetic profiles of the Bi-GdAlIG (BiGd₂Al_xFe_5-xO₁₂; 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 BiGd₂Al_0.7Fe_4.3O₁₂ nanoparticles demonstrate the enhanced coercivity of 320 Oe, which is factor of 2 larger than the x=0. The average size of the BiGd₂Al_0.5Fe_4.5O₁₂ nanoparticles was estimated 55 nm by Scherrer´s equation, and observed to be about 100 nm by scanning electron microscope image.