In a non-reciprocal circuit element, electric power handling capability is improved, and leakage power between adjacent channels is reduced. In addition, balance is taken between reduction of noise between adjacent ports and an increase in insertion loss. A non-reciprocal circuit element includes a YIG ferrite (10) and a plurality of conductors (15) disposed on the YIG ferrite (10) and intersecting each other in an insulated state. A part of Y of the YIG ferrite (10) is substituted with at least any one element of Ho, Dy, and Gd, or a part of Fe of the YIG ferrite (10) is substituted with Co.

A production method for a magnetic material, which is expressed by a chemical structure formula Fe(Al.sub.1xMn.sub.x).sub.2O.sub.4, where 0<x<1, and exhibits ferromagnetism, includes: preparing a mixed aqueous solution by dissolving, in distilled water, Fe nitrate, Al nitrate, and an oxide including Mn, the Fe nitrate, the Al nitrate, and the oxide being parent materials; preparing a metal-citric acid complex by mixing citric acid and ethylene glycol with the mixed aqueous solution; obtaining a precursor by boiling the metal-citric acid complex to a gel and drying the gel; and obtaining the magnetic material by sintering the precursor.

Devices and methods for below-resonance radio-frequency applications. In some embodiments, a ferrite device can include a modified yttrium iron garnet material in which bismuth occupies at least some of dodecahedral sites, and aluminum occupies at least some of tetrahedral sites.

Materials, devices and methods related to below-resonance radio-frequency (RF) circulators and isolators. In some embodiments, a circulator can include a conductor having a plurality of signal ports, and one or more magnets configured to provide a magnetic field. The circulator can further include one or more ferrite disks implemented relative to the conductor and the one or more magnets so that an RF signal can be routed selectively among the signal ports due to the magnetic field. Each of the one or more ferrite disks can include synthetic garnet material having dodecahedral sites, octahedral sites and tetrahedral sites, with bismuth (Bi) occupying at least some of the dodecahedral sites, and aluminum (Al) occupying at least some of the tetrahedral sites. Such synthetic garnet material can be represented by a formula Y.sub.3-x-2yzBi.sub.xCa.sub.2y+zFe.sub.5-y-z-aV.sub.yZr.sub.zAl.sub.aO.sub.12. In some embodiments, x1.4, y0.7, z0.7, and a0.75.