Magneto-Optic Measurements of Sputtered Thin Films with Perpendicular Magnetic Anisotropy

Layering Co and Pt is a known way to make magnetic thin films that display perpendicular magnetic anisotropy (PMA). Such films are useful in data storage and in spin-transfer torque devices. PMA is also a critical component to a proposed tunable spintronic terahertz emitting device where a layer with PMA will serve as a source of out-of-plane spin current upon ultrafast demagnetization from an intense laser pulse. As Pt is a heavy, 5d metal, it will scatter the spin current, and hence the top Pt layer must be replaced by a lighter metal, potentially resulting in an undesirable reduced PMA. We grew multi-layered samples using DC and RF sputter deposition on silicon substrates with a 1 nm Ta seed layer following parameters presented in literature [1], and achieved similar polar coercive field (Hcoer) results of about 15 mT while retaining a high degree of remanence. We examined two main variations: (1) a single Co layer: Pt2/Co1.2/Pt2 vs. Pt2/Co1.2/Cu2 vs Pt2/Co1.2/Pt2/Cu2 and (2) double Co layers: Pt2/Co1.2/Pt2/Co1.2/Cu2. The thickness per layer in nm is the number after each element. Hcoer of the (1) variation were 15.5 mT, 3.54 mT, and 11.6 mT, respectively. Hcoer of the (2) variation was 25.7 mT. Our results bode well for the path forward for the spintronic structures with strong PMA that also enable spin current transport for non-local manipulation of spin dynamics.

1. Ece Demirer, F., Lavrijsen, R., & Koopmans, B. (2021). An investigation of the interface and bulk contributions to the magneto-optic activity in Co/Pt multi-layered thin films. Journal of Applied Physics, 129(16), 163904. https://doi.org/10.1063/5.0047093