Substituted polyscrystalline YIG with very-low ferrimagnetic resonance linewidth and optical transparency

Polycrystalline garnets with room-temperature -band linewidth values below 4 Oe can reproducibly be prepared by reducing magnetocrystalline anisotropy and porosity to about zero values. The lowest linewidth which has been measured so far is Oe. Reduction of anisotropy can be accomplished by substitution of octahedral Fe³⁺ions by nonrelaxing ions of large enough ionic radius (In³⁺, Zr⁴⁺, Sn⁴⁺). Theoretical density and phase purity is achieved by simultaneous substitution of Y³⁺ions by Ca²⁺ions in combination with a tetravalention (Ge⁴⁺, Si⁴⁺, Zr⁴⁺, Sn⁴⁺) for charge compensation. In the different compositional series studied, low linewidth values can be obtained for a magnetization range of 1950 to 250 G. As a consequence of the phase purity and the complete absence of porosity, the perfect polycrystalline samples become transparent in the infrared "window" region of the Fe garnets.