Detection of in-plane magnetization switching of Ni80Fe20 layer by spin rectification effect

Abstract

Magnetization switching using spin orbit torque (SOT) [1] has been investigated intensively to realize the low power and high endurance magnetic memory. For the in-plane magnetization switching, fabrication of spin valves is generally required because the anomalous Hall effect is not applicable. Such an additional fabrication procedures impede the rapid development of material search for the materials that exhibit a large SOT. In this study we demonstrated SOT induced in-plane magnetization switching of a single Ni80Fe20 layer on platinum layer by using spin rectification effect (SRE). Under the microwave irradiation, dc voltage via SRE appears near the ferromagnetic resonance field, well known as the spin-torque FMR[2]. In contrast, non-zero dc voltage also appears around zero magnetic field due to the non-resonant SRE (nrSRE), whose voltage level corresponds to the magnetization direction [3]. We found that the nrSRE was drastically enhanced under the irradiation of microwave with a frequency lower than FMR condition. By using the enhanced nrSRE, we demonstrated a highly sensitive detection of in-plane magnetization switching even for a 100 nm-in-width Ni80Fe20 electrode. Figure 1 shows a schematic of the fabricated device. Firstly, a large magnetic field was applied along +y direction to initialize the magnetization direction. After removing the magnetic field, a low frequency microwave was applied to measure the initial DC voltage generated by the nrSRE. After stopping the microwave irradiation, a pulse current was applied into the Pt layer. Then, dc voltage induced by nrSRE was measured again to detect the magnetization reversal. Figure 2 shows the voltage difference between before and after application of the pulse current as a function of the pulse-current density. Clear voltage differences were obtained above 2.5×107 A/cm2, indicating successful magnetization switching. In the presentation, we will discuss the origin of the enhanced nrSRE.