High Quality and Large Size Yttrium Iron Garnet Crystal Grown by Top Seeded Solution Growth Technique

Abstract

Yttrium iron garnet (Y 3 Fe 5 O 12 , YIG) crystals have been widely used in microwave and magneto-optic devices due to their excellent magnetic and magneto-optical properties. Currently, the commercial material is YIG single crystal thin films, which is deposited on Gd 3 Ga 5 O 12 (GGG) substrate using liquid phase epitaxy technique.Herein, we report a new growth technology of YIG single crystal by top seeded solution growth (TSSG) technique from lead-free B 2 O 3 -BaF 2 flux. The maximum size and weight of the as-grown YIG crystal can be up to 43 mm× 46 mm×11 mm and 60 g, respectively. The crystals exhibit excellent comprehensive performances with narrow ferromagnetic resonance linewidth (0.679 Oe, 1 Oe=250/π A/m), high transparency (75%) and Faraday rotation angle (200 (°)•cm -1 @ 1310 nm and 160 (°)•cm -1 @1550 nm), indicating a good candidate in microwave and magneto-optic devices. More significantly, this growth technique is ideally suited to large size YIG or doped-YIG single crystals ascombined with the oriented seed crystal and lifting process, which can significantly decrease the manufacture cost.

Effect of Gadolinium Addition on Magnetic and Magneto-Optical Properties of Yttrium Iron Garnet Crystal

“…It can be seen from the hysteresis loop in Figure 4a that the saturation magnetization strength of GYIG crystal is approximately 14.4 emu/g, and the coercive field H c is approximately 8.7 Oe, which is significantly lower than that of YIG crystal. 9 The results of the hysteresis loop are also consistent with our speculation. The magnetization strength of the GYIG crystal can be saturated with very small magnetic fields, which facilitates the miniaturization of magneto-optical devices.…”

“…At 1310 and 1550 nm, the FRA of unannealed GYIG crystal was measured to be 174 and 130°/ cm, which have a slight reduction compared to YIG crystal. 9 We speculate that the reason may be that the addition of Gd 3+ ions changes the superexchange effect of the YIG system. At the same time, it may be the cause of the oxygen vacancy and Fe 2+ internal defects generated during the crystal growth process.…”

“…After annealing at 800 °C, the saturation magnetization intensity increases most significantly due to the most pronounced decrease in the Fe 2+ ion content. Figure b shows the relationship between saturation magnetization and temperature of GYIG crystal, it can be seen that the Curie temperature of the GYIG crystal has increased by about 15 K compared to the YIG crystal . Since the magnitude of the Curie temperature depends on the superexchange interactions between the magnetic moments, we know that the strongest superexchange interactions in the YIG crystal occur between Fe 3+ (a-site) and Fe 3+ (d-site) ions .…”

“…Figure 4b shows the relationship between saturation magnetization and temperature of GYIG crystal, it can be seen that the Curie temperature of the GYIG crystal has increased by about 15 K compared to the YIG crystal. 9 Since the magnitude of the Curie temperature depends on the superexchange interactions between the magnetic moments, we know that the strongest superexchange interactions in the YIG crystal occur between Fe 3+ (a-site) and Fe 3+ (d-site) ions. 34 Although exchange interactions between Fe 3+ (a-site) and Fe 3+ (a-site) ions as well as Fe 3+ (d-site) and Fe 3+ (d-site) ions also exist, they are negligible.…”

“…7,8 The commercial YIG crystals are reported to possess high Faraday rotation angle (FRA) at 1310 nm (220°/cm) and 1550 nm (180°/cm). 9 Compared to pure YIG crystals, rare earth-doped YIG crystals are expected to have better magnetooptical and magnetic properties. The general formula of the YIG crystal can be expressed as Y .…”