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 (E⊥c), resulted. A Co60γ irradiation was performed and the susceptibility was unchanged within experimental error.