Electrical detection of ferromagnetic resonance via rectification effects

Spin rectification effects are widely used to study magnetization dynamics in magnetic materials and spintronic devices. For instance, ferromagnetic resonance (FMR) can be easily detected by measuring a dc photovoltage resulting from the rectification of rf current in a ferromagnet with oscillating magnetization. Here we present an experimental study of the rectification effects produced by FMR in a ferromagnetic (NiFe, Fe) wire. A system of four independent nonmagnetic contact probes was used to supply both rf and dc currents to the wire and measure the resulting photovoltage at different locations in the wire. Our multiprobe system provided a means to separate contributions to the photovoltage from the ferromagnet/nonmagnet contacts and the bulk of the ferromagnet. The contact photovoltage was found to increase approximately linearly with the dc bias applied to the wire. In contrast, the bulk contribution was found to be almost independent of the dc bias. By tuning properties of individual contact probes we were able to change the magnitude of the contact photovoltage and even reverse its sign. Our results highlight the different contributions to photovoltage and the importance of contact properties/nonlinearities for rectification effects in spintronic devices.