Damping Constants of Ni-Fe and Ni-Co Alloy Thin Films

Abstract

Gilbert's damping constants, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$alpha$</tex> , of Ni-Fe and Ni-Co thin films are determined by Q-band ferromagnetic resonance (FMR) analysis. <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$alpha$</tex> is calculated from the resonance width of the FMR spectrum. <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$alpha$</tex> of Ni <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$_85$</tex> Fe <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$_15$</tex> film is found to be 0.0034, which is one-fourth of those of Ni film <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(alpha =0.013)$</tex> and Co <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(alpha =0.013)$</tex> . <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$alpha$</tex> of the Ni <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$_100 - x$</tex> Co <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$_ x$</tex> specimens increases with decreasing the Co concentration from 100 to 68 at%, and the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$alpha$</tex> value of Ni <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$_32$</tex> Co <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$_68$</tex> film has the maximum value of 0.0021. The <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$alpha$</tex> values of the Ni-Co specimens are nearly the same as those of the Co-Cr-Ta and the Co-Cr-Pt.