Magnetic anisotropy of phase-separated CaO–Fe3O4–SiO2 glasses prepared from a two-liquids immiscible melt

The phase-separated glass containing magnetite in CaO–Fe3O4–SiO2 system was prepared through liquid–liquid stable immiscibility. Possibilities of the distortion of the phase-separation texture by elongation during quenching were investigated in order to introduce magnetic anisotropy in the glass. The sintered rods of raw materials were melted at 2200 °C first for homogenizing the liquid melt, and subsequently melted at 1800 °C where the melt was in the stable immiscible region, in order to produce two liquid phases by separation. The glass samples were finally prepared by quenching the phase-separated melts with and without elongation. The quenched sample without elongation showed spinodal-type interconnected texture, whereas the elongated sample showed a phase-separation texture of needle-like CaO–Fe3O4-rich phase that was oriented in the direction of elongation. The precipitated magnetite was found in the stretched CaO–Fe3O4-rich phase. The elongated glass showed the obvious uniaxial magnetic anisotropy, which is not attributed to magnetocrystalline anisotropy of magnetite but to shape magnetic anisotropy due to the stretched magnetic phase containing magnetite. These results suggest that the deformation and orientation of the phase-separation texture can introduce a magnetic anisotropy in isotropic glass materials.