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

Abstract

Polycrystalline garnets with room-temperature <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</tex> -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 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\DeltaH = 1.7</tex> Oe. Reduction of anisotropy can be accomplished by substitution of octahedral Fe <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> ions by nonrelaxing ions of large enough ionic radius (In <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> , Zr <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4+</sup> , Sn <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4+</sup> ). Theoretical density and phase purity is achieved by simultaneous substitution of Y <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> ions by Ca <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> ions in combination with a tetravalention (Ge <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4+</sup> , Si <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4+</sup> , Zr <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4+</sup> , Sn <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4+</sup> ) 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.