Magneto-optic insulators utilizing the optical activity of Co<sup>++</sup>(T<inf>d</inf>)

Abstract

Large magneto-optic effects are associated with the crystal field transitions of Co++(T <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</inf> ) in a variety of spinel oxides. In the oxides, the F and P crystal field bands peak at about 1.5 and 0.6 μm, respectively. Many iron-containing quaternary compounds (CoT <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> Fe <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2-x</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> ) have transition temperatures above ambient. Here, T is a trivalent metal ion such as Cr <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> or Rh <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> . Room-temperature magneto-optic measurements on a number of these compounds indicate peak Faraday effects in the range of 0.5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> to 1.0 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> (deg/cm) at about 0.6 μm. The Curie temperature may be adjusted by the compositional parameter x and normal remanence of the surface Kerr effects are observed. The latter properties are potentially useful for optical memory devices. These materials are considered for isolation and modulation devices in the 5.0 to 12.0 μm wavelength range.