Damping constants of Co-Cr-Ta and Co-Cr-Pt thin films

Abstract

Gilbert's damping constants, α , of Co-Cr-Ta and Co-Cr-Pt thin films are determined by Q-band FMR analysis using single crystal magnetic thin films epitaxialIy grown on MgO(110) substrates. α is calculated from the resonance width of the FMR spectrum. α of Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">77</sub> Cr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">19</sub> Ta <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> is found to increase from 0.016 to 0.028 as magnetic layer thickness increases from 25 to 240 nm. α also increases from 0.009 to 0.019 when the Cr concentration in the 60 nm thick Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">96-x</sub> Cr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Ta <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> magnetic layer is increased from 8 to 19 at.%. The 25 nm thick Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">81</sub> Cr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15</sub> Pt <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> , film has a 2.5 times larger α value (0.038) than the Co <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">81</sub> Cr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15</sub> Ta <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> film (α = 0.014) with the same thickness.