Ferromagnetic Resonance in Garnet Y₃Fe5-xCox/2Gex/2O₁₂

The substitution of a small amount of Co 2+ and Ge 4+ for Fe 3+ in yttrium iron garnet causes remarkable changes of the magnetic anisotropy constants and Δ H . The magnetic anisotropy constants K 1 and K 2 of Y 3 Fe 5- x Co x /2 Ge x /2 O 12 depend strongly on temperature, and K 1 is linear to the concentration of cobalt at a given temperature, where x =0, 0.0042, 0.017, 0.048. The effect of cobalt substitution is similar to the case of magnetite containing cobalt, and can be accounted for by Slonczewski's theory with the value of the parameter |αλ|=100 cm -1 . The line width Δ H increases with the increase in cobalt concentration.