Resonant current-in-plane spin-torque diode effect in magnet$-$normal metal bilayers

Abstract

Via the spin-Hall effect and its inverse, in-plane charge currents in a normal metal$-$ferromagnet (N$|$F) bilayer can be used to excite and detect magnetization dynamics in F. Using a magneto-electric circuit approach, we here consider the current response to quadratic order in the applied electric field, which is resonantly enhanced for driving frequencies close to frequencies of coherent magnetization modes. Our theory can be applied to bilayers with a magnetic insulator or with a magnetic metal. It focuses on the contribution of coherent magnetization dynamics to spin currents collinear with the equilibrium magnetization direction, but also takes into account relaxation of spin accumulation via spin currents carried by incoherent magnons and conduction electrons in F.