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

Abstract

Magnetic garnets with Bi3+ are the standard media of discrete Faraday rotation isolators for IR-laser∕fiber-optical transmission at 1.55μm wavelength. For monolithic integration with semiconductors, perovskites of generic formula A[B]O3 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° 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 {A3+A′4+}[Fe3+Ni2+]O6. The other concept relies on ferromagnetism through delocalization superexchange with the composition A23+[Mn4+Ni2+]O6. Where appropriate to enhance Faraday rotation, Bi3+ can be used for A3+.

Structural, magnetic, and optical properties ofBiFeO3andBi2FeMnO6Bi1, Taussig2, Kim3 et al. 2008Phys. Rev. BSelf Cite165131022View full textAdd to dashboardCite

“…Due to their good lattice match with silicon, perovskite materials, especially orthoferrites ͑AFeO 3 ͒, might be suitable candidates for integrated isolators. 12 In order to obtain high Faraday rotation in perovskites, one has to line up most of the orbital angular momentum vectors of the active ionic electric dipoles along a macroscopic direction. This is usually achieved by spinorbit coupling in a ferromagnetic or ferrimagnetic material.…”

“…In ordered double perovskites with Curie temperature ͑T C ͒ above RT, the spins and orbital angular momentum vectors of the two types of GGA+ U-site ions align along their own macroscopic directions when magnetized, providing a net Faraday rotation at certain wavelengths. 12 Meanwhile, Bi 3+ ions have strong covalent interactions with the octahedral complexes, which enhance the nondegeneracy of the spin-orbit coupling levels as well as the Faraday rotation of the material. 13,14 Among the bismuth perovskites, perhaps BiFeO 3 is the most systematically studied.…”

Dependence of Faraday rotation and magneto-optical figure of merit on dielectric tensor elements in materials with uniaxial symmetry

“…Orthoferrites, however, have only this single octahedral transition; so, given the same strong internal magnetic field, significantly higher figures of merit should be achievable. Although bismuth orthoferrite, for instance, is an antiferromagnet with a low net moment due to spin canting, 15 the partial substitution of various transition metal cations on the Fe site may induce a large enough internal field to lead to significant values of F. 11,16 If we relax the assumption of a uniaxial material and allow the two nontrivial diagonal components to differ ͑i.e., ⑀ xx ⑀ yy ͒, however, the material quickly becomes birefringent and F becomes less useful by itself. As discussed in Ref.…”

Oxygen partial pressure dependence of magnetic, optical and magneto-optical properties of epitaxial cobalt-substituted SrTiO_3 films

“…Transition metal substituted STO films, such as Sr(Ti,Co)O 3-δ [3], (La,Sr)(Ti,Co)O 3-δ [5][6][7], and Sr(Ti,Fe)O 3-δ (STF) [8][9][10][11], exhibit room temperature magnetic and magneto-optical (MO) properties which depend on substrate, substituent type and concentration, buffer layer and film growth conditions. Faraday rotation of substituted STO films make these films attractive for integrated non-reciprocal photonic device applications [12,13] such as isolators and circulators as well as for fundamental investigations of the spectral origins of MO properties and superexchange effects [9,[14][15][16]. Substituted STO films can be grown both as polycrystalline films on Si or as single crystals on perovskite substrates, but on CeO 2 /yttriastabilized zirconia buffered Si, STF films grew with two different epitaxial orientations, forming so-called double-epitaxial growth in which the (100)-oriented film contained (110) crystals which formed to relieve strain [17].…”