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Rare-earth iron garnets with large magnetic gyrotropy, made with reduced thermal budgets, are ideal magneto-optical materials for integrated isolators. However, reduced thermal budgets impact Faraday rotation by limiting crystallization, and characterization of crystallinity is limited by resolution or scannable area. Here, electron backscatter diffraction (EBSD) is used to measure crystallinity in cerium substituted yttrium- and terbium-iron garnets (CeYIG and CeTbIG) grown on planar Si, crystallized using one-step rapid thermal processes, leading to large Faraday rotations > −3500 °/cm at 1550 nm. Varying degrees of crystallinity are observed in planar Si and patterned Si waveguides, and specific dependences of crystallite size are attributed to the nucleation/growth processes of the garnets and the lateral dimensions of the waveguide. On the other hand, a low thermal budget alternative–exfoliated CeTbIG nanosheets–are fully crystalline and maintain high Faraday rotations of −3200 °/cm on par with monolithically integrated thin film garnets.
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Magneto‐Optical Bi‐Substituted Yttrium and Terbium Iron Garnets for On‐Chip Crystallization via Microheaters
Abstract Ferrimagnetic iron garnets enable magnetic and magneto‐optical functionality in silicon photonics and electronics. However, garnets require high‐temperature processing for crystallization which can degrade other devices on the wafer. Here bismuth‐substituted yttrium and terbium iron garnet (Bi‐YIG and Bi‐TbIG) films are demonstrated with good magneto‐optical performance and perpendicular magnetic anisotropy (PMA) crystallized by a microheater built on a Si chip or by rapid thermal annealing. The Bi‐TbIG film crystallizes on Si at 873 K without a seed layer and exhibits good magneto‐optical properties with Faraday rotation (FR) of −1700 deg cm−1. The Bi‐YIG film also crystallizes on Si and fused SiO2at 873 K without a seed layer. Rapidly cooled films exhibit PMA due to the tensile stress caused by the thermal expansion mismatch with the substrates, increasing the magnetoelastic anisotropy by 4 kJ m−3versus slow‐cooled films. Annealing in the air for 15 s using the microheater yields fully crystallized Bi‐TbIG on the Si chip.
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- PAR ID:
- 10538445
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Advanced Optical Materials
- ISSN:
- 2195-1071
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1002/adom.202400708
