Microwave dynamics in nanoscale multilayer CPP devices driven by spin-transfer torque

摘要

Nanopillar devices with an elliptical cross-section of about 130 nm /spl times/ 70 nm were studied. The devices were made by ion milling of a sputtered multilayer Cu 80 nm/Py 20 nm/Cu 6 nm/Py 2 nm/Cu 2 nm/Pt 30 nm (Py=Ni/sub 80/Fe/sub 20/) followed by planarization with silicon oxide and the deposition of a Cu top contact. Current is applied perpendicular to the sample layers. We used Py magnetic layers due to its low magnetocrystalline anisotropy and small magnetostriction. As compared to previous studies of Co samples, the small magnetic moment of Py leads to smaller critical currents I/sub c/ for switching or excitation of dynamical states and smaller coercive magnetic fields H/sub c/. This allows us to study nanopillar devices over an effectively larger range of current and field than in previous experiments.