Microstructure, magnetic, and magneto-optical properties of chemical synthesized Co–RE (RE=Ho, Er, Tm, Yb, Lu) ferrite nanocrystalline films

Abstract

The sol-gel synthesis of Co–RE $(\mathrm{RE=Ho, Er, Tm, Yb, Lu})$ ferrite nanocrystalline films was accomplished on monocrystalline silicon substrates, and the influence of RE ions on structure, magnetic, and magneto-optical (MO) properties of the resultant ferrites was examined. The results obtained reveal that, when $\text{x⩽0.2,}$ the ${\mathrm{CoFe}}_{\text{2−x}}{\mathrm{RE}}_x{\mathrm{O}}_{\mathrm{4}}$ ferrite films have pure spinel phase with slightly enlarged cell constants and lattice distortion due to the large radii of RE ions. The RE ions tend to decrease the room-temperature magnetization as well as the Curie point of products, and may have a certain contribution to coercive force except for a nonmagnetic ${\mathrm{Lu}}^{\mathrm{3+}}$ ion. For the present optical structure in which MO layers are substrated on silica, Co–RE ferrite films show the peak Kerr rotation at a shorter wavelength than the ${\mathrm{CoFe}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{4}}$ film, and Er or Tm doped samples exhibit an interesting enhancement of the MO effect.