In each Y3Fe2(FeO4)3 formula unit, two octahedral Fe3+ ions and three tetrahedral Fe3+ ions align antiparallel, leaving a net ferrimagnetic moment of one Fe3+ spin per formula unit below Tc = 560 K (287 °C).
Grown as bulk single crystals or liquid-phase-epitaxy thin films, YIG exhibits the narrowest known ferromagnetic-resonance linewidth and highest microwave Q factor, powering tunable YIG sphere bandpass filters and oscillators.
Its high Verdet constant and infrared transparency above 600–1,200 nm make YIG a standard material for optical Faraday rotators, isolators, and magneto-optical imaging of superconductors.