Study on the Formation Mechanism of Pit Defects and Their Influence on Magneto-optical Properties in (TbYbBi)3Fe5O12 Crystals Grown by the LPE Method

In recent years, with the rapid development of optical transmission networks and data center construction, higher demands have been placed on the stability of magneto-optical crystal materials. To reduce defects in the growth of rare-earth iron garnets and improve the stability of their magneto-optical properties, this study explored the formation mechanism of pit defects and their impact on the properties of rare-earth iron garnet crystals. In this paper, a series of high magneto-optical quality 4-in. thick rare-earth iron garnet single-crystal films with the composition (TbYbBi)₃Fe₅O₁₂ were successfully grown by liquid-phase epitaxy. Etching the crystals in high-concentration hydrochloric acid yielded corrosion pits with regular hexagonal shapes, and detection showed that the Pt content in these pits was 15%, which is much higher than that in other areas outside the pits. Moreover, by combining the morphologies of pit defects at different thicknesses, the formation and development mechanisms of pit defects were clarified. Tests confirmed that pit defects have no significant impact on the magneto-optical properties of the crystal at specific wavelengths and temperatures. However, they reduce the stability of (TbYbBi)₃Fe₅O₁₂ crystals in environments with variable wavelengths and temperatures: specifically, the wavelength coefficient increased by 4% at 1550 nm, and the temperature coefficient rose by approximately 11% at 60 °C.