Microwave relaxation properties of substituted lithium ferrite

Abstract

The effect of Co, Mn, Ti, and Al substitutions on two important microwave relaxation parameters, the spin-wave linewidth ΔH <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</inf> and the high field effective linewidth ΔH <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eff</inf> , for lithium ferrite, Li <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</inf> Fe <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2.5</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> , has been examined. Cobalt tends to increase both linewidths, while Mn tends to decrease them. The quantitative dependences, however, indicate that an optimum Mn level, at about 0.5 at./F.U., serves to maximize the ratio ΔH <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</inf> /ΔH <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eff</inf> . There is no marked change in the effect of cobalt on either linewidth parameter as Ti and/or Al substitutions are made to reduce the saturation induction. However, Ti substitutions are found to substantially decrease ΔH <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</inf> , while causing a moderate (factor of two) increase in ΔH <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eff</inf> .