Annealing effect and interlayer modulation on magnetic damping of CoFeB/interlayer/Pt thin films

摘要

The annealing effect and interlayer (IL) modulation on the magnetic damping properties of CoFeB/IL/Pt (IL = Ta or Ru) multilayers have been systematically studied by the time-resolved magneto-optical Kerr effect. It is found that after inserting a thin IL, the saturated magnetic damping factor alpha(s) drops considerably due to the reduced spin pumping effect. By fitting the curves of alpha(s) versus IL thickness, spin diffusion lengths of Ta and Ru are determined to be 3.07 and 3.59 nm, respectively. Interestingly, for the CoFeB samples with different capping layers of Pt, Ta/Pt, or Ru/Pt, the alpha(s) values exhibit an identical non-monotonic variation tendency alpha(s) annealing temperature (T-a) increases. It first rises to a maximum at Ta similar to 100 degrees C and then decreases, reaching a minimum value (alpha(s) = 0.021-0.011) at T-a similar to 300 degrees C. After that, alpha(s) starts to increase again. Such a complicated variation behavior is attributed to two-magnon scattering contribution, which originates from the change in the CoFeB surface roughness and interfacial atomic intermixing induced by thermal annealing. This study provides a deep understanding and effective control of magnetic damping for practical design of high performance spintronic devices. Published by AIP Publishing.