Magnetic Susceptibility and Optical Studies of Cr3+ in Al2O3 (Ruby): Magnetic Method for Determing Concentration

Magnetic‐susceptibility and optical‐absorption measurements were performed on ruby samples of varying chromium concentration. Susceptibilities were measured by the Faraday method, both with and without selective microwave saturation of the Cr³⁺ susceptibility at resonance. The susceptibility values were used to calculate the Cr³⁺ concentrations, and these together with the optical absorption were used to obtain the ``molar'' absorption coefficients. The absorption coefficient of 50 cm⁻¹/wt% equivalent Cr₂O₃, for both the 0.40‐ and 0.56‐μm band maxima $\mathrm{(E\perp c)}$ , resulted. A Co⁶⁰γ irradiation was performed and the susceptibility was unchanged within experimental error.