Contact and bulk rectification effects in ferromagnetic resonance experiments

TL;DR

This study investigates how contact and bulk effects influence spin rectification voltages in ferromagnetic resonance experiments on NiFe wires, emphasizing the role of contact properties and nonlinearities in spintronic devices.

Contribution

It introduces a four-probe measurement system to distinguish contact and bulk contributions to rectification effects in ferromagnetic resonance experiments.

Findings

Contact photovoltage increases linearly with dc bias.

Bulk contribution remains nearly independent of dc bias.

Adjusting contact properties can reverse photovoltage sign.

Abstract

We present an experimental study of the spin rectification effects produced by ferromagnetic resonance in a NiFe wire. A system of four independent nonmagnetic contact probes was used to supply both rf and dc currents to the wire and to measure dc voltages at different locations in the wire. The rf current drives the ferromagnet's magnetization into resonance and produces a dc photovoltage which results from the rectification of rf current in the ferromagnet with oscillating magnetization. Our 4-probe system provided a means to detect the photovoltage and separate contributions 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.