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

Gilbert's damping constants, alpha, of Co-Cr-Ta and Co-Cr-Pt thin films are determined by Q-band FMR analysis using single crystal magnetic thin films epitaxially grown on MgO(110) substrates. alpha is calculated from the resonance width of the FMR spectrum. alpha of Co77Cr19Ta4 is found to increase form 0.016 to 0.028 as magnetic layer thickness increases from 25 to 240 nm. alpha also increases from 0.009 to 0.019 when the Cr concentration in the 60 nm thick Co96-xCrxTa4 magnetic layer is increased from 8 to 19 at.%. The 25 nm thick Co81Cr15Pt4 film has a 2.5 times larger alpha value (0.038) than the Co81Cr15Ta4 film (alpha = 0.014) with the same thickness.