Determination of the magnetic compensation composition in Al-substituted Bi-DyCoIG nanoparticles with enhanced coercive-force

In garnet particles, higher coercive-force is required to develop a practical magnetooptical storage media. Therefore, in this paper, we develop high coercive-force particles reflecting the magnetic compensation induced by the aluminum substitution, and increasing the magnetic anisotropy under the influence of cobalt substitution for applying the garnet particles to magnetooptical storage media. Nanoparticles of aluminum substituted bismuth dysprosium cobalt iron garnet (Bi-DyCoAlIG) exhibit a magnetic compensation at room temperature. The Bi-DyCoAlIG (BiDy₂Co_0.2Al_xFe_4.8-xO₁₂: 0≤x≤0.9) nanoparticles were made using coprecipitation and heat-treatment processes. The X-ray diffraction patterns of nanoparticles are clear that all the peaks were assigned to the single phase of the garnet structure. The particles size of the Bi-DyCoAlIG nanoparticles was observed to be less than 30 nm by transmitted electron microscope images which is comparables to the estimated average particle size of Scherrer\´s equation. The magnetic profiles of the Bi-DyCoAlIG nanoparticles show shallow minima at the composition range of 0.62Co_0.2Al_0.7Fe_4.1O₁₂ nanoparticles demonstrate the enhanced coercivity of 1000 Oe which is factor of 3 larger than the x=0.