Spin-torque induced oscillation of a magnetoresistive nanopillar with a conically magnetized free layer and an in-plane magnetized reference layer

Spin-torque induced magnetization dynamics in a magnetoresistive nanopillar with a conically magnetized free layer and an in-plane magnetized reference layer is theoretically studied. Two modes are observed for zero-bias-field self-oscillation, the occurrence of which depends on applied current density: one is the in-plane oscillation mode at small current density and the other is the out-of-plane oscillation mode at large current density. The mechanism for the appearance of these oscillation modes are explained, and the critical current densities of the modes are presented. (author)