Iron-based garnet films that have large magneto-optical (MO) effect are a promising material for MO device applications. In particular, terbium iron garnet (TbIG) can crystallize directly on a Si substrate without garnet seed layers [1-4] and, therefore, recent investigations show quite practical optical isolators taking advantage of TbIG [1,2]. However, crystallization for TbIG requires high temperatures and it is desirable to limit the heating to those regions of the chip where devices are formed. In this study, we compare the structure, magnetic and MO properties of TbIG and Bi doped TbIG (Bi-TbIG) films processed by rapid thermal annealing (RTA) to those annealed locally using an embedded resistor with 40-μm-square area. TbIG (Tb2.77Fe5O12) and Bi-TbIG (Bi0.02Tb2.82Fe5O12) films are made by pulsed laser deposition at room temperature, which allows for liftoff patterning using a photoresist mask. The crystal structure for the films is characterized by micro-Raman spectroscopy and X-ray diffraction (XRD) and the magnetic properties by vibrating sample magnetometry. XRD shows single phase garnet after RTA 1073 – 1273 K. Raman spectra for Bi-TbIG film before/after 1173 K annealing and for the Si substrate are shown in Fig. 1. The Raman spectrum for the as deposited film is almost the same as that of the Si substrate while a Raman peak corresponding to the strongest peak of TbIG (Eg) is observed around 261 cm-1 in the annealed film. Raman spectroscopy enables detection of local crystallization in Bi-TbIG on embedded resistors. Figure 2 shows room temperature in-plane M-H loops of the annealed TbIG and Bi-TbIG films. The TbIG film is not saturated at 1 T while the Bi-TbIG is saturated at 0.7 T. Coercivity in TbIG rapidly increases in the vicinity of the compensation temperature (Tcomp) [3] which is ~250 K for bulk TbIG, and slightly lower for thin film TbIG with Tb deficiency [4]. Bi doping lowers (Tcomp) further [4] explaining the easier saturation of the Bi-TbIG film. The high figure of merit of Bi-TbIG and its higher remanence make this material attractive for integrated photonic devices.

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Crystallization of magneto-optical bismuth terbium iron garnet films

**Session chair:** Shawn Pollard, The University of Memphis


FPD - Magnetooptics II

poster

The 15th Joint MMM-INTERMAG Conference (2022 Joint) is sponsored jointly by AIP Publishing and the IEEE Magnetics Society. Members of the international scientific and engineering communities interested in recent developments in fundamental and applied magnetism are invited to attend and contribute to the technical sessions. The technical program will include invited and contributed papers in oral and poster sessions, invited symposia, a plenary session, and an evening session, with about 1500 presentations overall. This Conference provides an outstanding opportunity for worldwide participants to meet their colleagues and collaborators and discuss developments in all areas of magnetism research.

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This Conference provides an outstanding opportunity for worldwide participants to meet their colleagues and collaborators and discuss developments in all areas of magnetism research.

Juejun Hu

1

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Crystallization of magneto-optical bismuth terbium iron garnet films

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