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Register a new userMagnetocrystalline anisotropy, Dzyaloshinskii-Moriya interaction, and orbital moment anisotropy in W/Co/Pt trilayers
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We have studied the Co layer thickness dependences of magnetocrystalline anisotropy (MCA), Dzyaloshinskii-Moriya interaction (DMI), and orbital moment anisotropy (OMA) in W/Co/Pt trilayers. We find the MCA favors magnetization along the film normal and monotonically increases with decreasing effective magnetic layer thickness ($t_mathrm{eff}$). The magnitude of the Dzyaloshinskii-Moriya exchange constant ($|D|$) increases with decreasing $t_mathrm{eff}$ until $t_mathrm{eff} sim$1 nm, below which $|D|$ decreases. MCA and $|D|$ scale with $1/t_mathrm{eff}$ for $t_mathrm{eff}$ larger than $sim$1.0 nm, indicating an interfacial origin. To clarify the cause of the $t_mathrm{eff}$ dependences of MCA and DMI, the OMA of Co in W/Co/Pt trilayers is studied using x-ray magnetic circular dichroism (XMCD). We find non-zero OMA when $t_mathrm{eff}$ is smaller than $sim$0.8 nm. The OMA increases with decreasing $t_mathrm{eff}$ at a rate that is larger than what is expected from the MCA and Brunos formula, indicating that other factors contribute to the MCA at small $t_mathrm{eff}$ to break the $1/t_mathrm{eff}$ scaling. The $t_mathrm{eff}$ dependence of the OMA also suggests that $|D|$ at $t_mathrm{eff}$ smaller than $sim$1 nm is independent of the OMA at the interface. We consider the growth of Co on W results in a strain that reduces the interfacial MCA and DMI at small $t_mathrm{eff}$, indicating the importance of lattice structure to control their properties.
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