Anisotropy and Faraday effect in Co spinel ferrite films

Abstract

Crystalline Co spinel ferrite films were prepared by rf sputtering on glass substrates without buffer layer and annealed at temperatures from 400 to 600 °C for 2 h in air. (100) texture was obtained in these films. The anisotropy constant, magnetic hysteresis loops, and magneto‐optical Faraday spectra of the films were measured. The texture became poor when the films were annealed below 500 °C, but the perpendicular anisotropy constant K_u, squareness ratio R=(Mr/Ms)_⊥/(Mr/Ms)_∥ increased and showed peak values of 2.2×10⁵ ergs/cm³ and 0.94, respectively, at an annealing temperature T_a=500 °C. For the film annealed at 600 °C (higher than the Curie temperature, 520 °C, of Co spinel ferrite), the texture recovered, but K_u and R dropped. The Faraday rotation spectra of Co spinel ferrite films showed a broad peak centered around 720 nm. The peak value increased monotonically with increasing annealing temperature. These results may be related to the Co ion‐induced anisotropy and Co ion distribution in tetrahedral sites and octahedral sites.