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Cerium-doped terbium iron garnet (CeTbIG) thin films with varying compositions and thicknesses were deposited to determine a garnet formation region. Both grain size and Faraday rotation (FR) increased in this region as the Ce content increased until 20% of the dodecahedral sites were occupied by Ce. The high Ce content was achieved by lowering the Fe ratio with respect to the total rare earth content. Above 20% Ce, the Faraday rotation was relatively independent of composition at -830^o/cm, which is similar in magnitude to positive Faraday rotation garnets, e.g.: + 600^o/cm for undoped TbIG. Next, we found that a two-step annealing method, involving a 400°C pre-anneal followed by higher temperatures, effectively reduced the maximum temperature from 900°C to 800°C without decreasing the Faraday rotation. Finally, a Si-integrated interferometer was simulated using the stable (+) and (-) Faraday rotation materials developed in this work. The simulation identified a Si-integrated Mach Zehnder Interferometers (MZI) with “push/pull” nonreciprocal phase shifts (NRPS) of opposite signs that enable mm-scale with zero external magnetic field (field-free). 

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. 

Magnetic nanowires (MNWs) rank among the most promising multifunctional magnetic nanomaterials for nanobarcoding applications, especially biolabeling, owing to their nontoxicity and remote excitation using a single magnetic source. Until recently, the first-order reversal curve (FORC) technique has been broadly used to study the MNWs for biolabeling applications. However, since FORC measurements require many data points, this technique is very slow which makes it inapplicable for clinical use. For this reason, we recently developed a fast new framework, named the projection method, to measure the irreversible switching field (ISF) distributions of MNWs as the magnetic signature for the demultiplexing of magnetic biopolymers. Here, we illustrate the ISF distributions of several MNWs types in terms of their coercivity and interaction fields, which are characterized using both FORC and projection methods. Then, we explain how to tailor the ISF distributions to generate distinct signature to reliably and quantitatively demultiplex the magnetically enriched biopolymers. 

Abstract One of the best magneto‐optical claddings for optical isolators in photonic integrated circuits is sputter deposited cerium‐doped terbium iron garnet (Ce:TbIG) which has a large Faraday rotation (≈−3500° cm⁻¹at 1550 nm). Near‐ideal stoichiometry of Ce_0.5Tb_2.5Fe_4.75O₁₂is found to have a 44 nm magnetic dead layer that can impede the interaction of propagating modes with garnet claddings. The effective anisotropy of Ce:TbIG on Si is also important, but calculations using bulk thermal mismatch overestimate the effective anisotropy. Here, X‐ray diffraction measurements yield highly accurate measurements of strain that show anisotropy favors an in‐plane magnetization in agreement with the positive magnetostriction of Ce:TbIG. Upon doping TbIG with Ce, a slight decrease in compensation temperature occurs which points to preferential rare‐earth occupation in dodecahedral sites and an absence of cation redistribution between different lattice sites. The high Faraday rotation, large remanent ratio, large coercivity, and preferential in‐plane magnetization enable Ce:TbIG to be an in‐plane latched garnet, immune to stray fields with magnetization collinear to direction of light propagation.