Interfacial and Bulk Magnetic Properties of Stoichiometric Cerium Doped Terbium Iron Garnet Polycrystalline Thin Films

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⁻¹ at 1550 nm). Near-ideal stoichiometry (Formula presented.) of Ce_0.5Tb_2.5Fe_4.75O₁₂ is 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.