Magneto-optic property measurement of bismuth substituted yttrium iron garnet films prepared by metal-organic-decomposition method at the 1310-nm and 1550-nm wavelengths

We have measured the magneto-optic (MO) properties of film-type bismuth substituted yttrium iron garnets (Bi1.5:YIG, Bi1.5Y1.5Fe5O12) prepared by using metal-organic-decomposition (MOD) method on glass substrates at the 1310-nm and 1550-nm wavelengths. The Verdet constant of the Bi1.5:YIG film in the unsaturated linear magnetization region has been experimentally determined from a sensitive measurement of the Faraday rotation of the Bi1.5:YIG films with a lock-in amplifier and an auto-balanced photoreceiver under alternating magnetic fields. The Bi:YIG films have been deposited on silica glass substrates without any buffer layer and with one of buffer layers of Bi1Y2Fe5O12 (Bi1:YIG) and Bi1Fe4Ga1Nd2O12 (Bi1:NIGG) which are used to compensate mismatch of the lattice constant and thermal expansion coefficient between the film and substrate. The maximum value of the measured Faraday rotation of the Bi1.5:YIG film was over 94.6 and 156.5 °/cm for an applied unsaturated magnetic field of 100 Gauss at wavelengths of 1310 and 1550 nm, respectively, when it was prepared at annealing temperature of 700 °C and annealing speed of 1 °C/min. The absorption coefficients of the Bi1.5:YIG films were measured to be 70 cm−1 and 330 cm−1, respectively, at each of the wavelengths, and the average Gilbert damping coefficient of the Bi1.5:YIG film with a Bi1:NIGG buffer layer was measured to be 6.42 ± 18.09 × 10−4 (with the minimum value of 0 and the maximum value of 24.51 × 10−4) from a conventional ferromagnetic resonance (FMR) measurement system. Our experimental result indicates that the magneto-optic property of the Bi:YIG films prepared by the MOD method is unstable and fluctuates from run to run although its average magnetic property may be useful for application to compact integrated optical isolators under an easy solution-based fabrication process.