Mixed-cation designs of magnetic perovskites for Faraday rotation at IR wavelengths

Magnetic garnets with Bi3+ are the standard media of discrete Faraday rotation isolators for IR-laser/fiber-optical transmission at 1.55 mu m wavelength. For monolithic integration with semiconductors, perovskites of generic formula A[B]O-3 offer promising alternatives that involve combinations of select transition-metal ions in octahedral B sites. In this paper, two concepts are described. In both cases, the 180 degrees B-O-B bonding of the perovskite lattice could provide superexchange fields large enough to maintain spin ordering at room temperature. One model proposes a quasiferrite arrangement with antiferromagnetic alignment between Fe3+ and Ni2+ charge ordered in the double perovskite compound {A(3+)A('4+)}[Fe3+Ni2+]O-6. The other concept relies on ferromagnetism through delocalization superexchange with the composition A(2)(3+)[Mn4+Ni2+]O-6. Where appropriate to enhance Faraday rotation, Bi3+ can be used for A(3+).