Effect of very thin Cr underlayers on the micromagnetic structure of RF sputtered CoCrTa thin films

The effects of very thin Cr underlayers on the initial susceptibilities and micromagnetic structures of RF sputtered CoCrTa thin films have been studied. It was found that the initial susceptibility of the CoCrTa films on thin Cr underlayers is a factor of 2.5 to 3.5 times smaller than the value of the CoCrTa film without any Cr underlayer. The micromagnetic images of these CoCrTa films on thin Cr underlayers also exhibit a different feature from the CoCrTa film deposited on substrate with no Cr underlayer. The thicker the Cr underlayers, the finer are the micromagnetic images observed at both the as-deposited and the remanent state. It is very likely that the Cr underlayers induce stress in the CoCrTa/Cr double-layer thin films, and, through magnetoelastic interactions, the micromagnetic structures will be refined by the formation of barriers which pin the domain walls. This model could explain the low initial susceptibility and high in-plane coercivity in the RF-sputtered thin CoCrTa/Cr double layer films