Real-time Hall-effect detection of current-induced magnetization dynamics in ferrimagnets

G Sala,C.-H Lambert,E Grimaldi,V Krizakova,T Devolder,P Gambardella

doi:10.1038/s41467-021-20968-0

Abstract

Measurements of the transverse Hall resistance are widely used to investigate electron transport, magnetization phenomena, and topological quantum states. Owing to the difficulty of probing transient changes of the transverse resistance, the vast majority of Hall effect experiments are carried out in stationary conditions using either dc or ac. Here we present an approach to perform time-resolved measurements of the transient Hall resistance during current-pulse injection with sub-nanosecond temporal resolution. We apply this technique to investigate in real-time the magnetization reversal caused by spin-orbit torques in ferrimagnetic GdFeCo dots. Single-shot Hall effect measurements show that the current-induced switching of GdFeCo is widely distributed in time and characterized by significant activation delays, which limit the total switching speed despite the high domain-wall velocity typical of ferrimagnets. Our method applies to a broad range of current-induced phenomena and can be combined with non-electrical excitations to perform pump-probe Hall effect measurements.

Highlights

Measurements of the transverse Hall resistance are widely used to investigate electron transport, magnetization phenomena, and topological quantum states
We demonstrate the capability of this technique by studying the magnetization dynamics triggered by SOTs17 in ferrimagnetic GdFeCo dots patterned over a Pt Hall bar
We have demonstrated a technique to perform time-resolved measurements of the Hall effect and transverse magnetoresistive signals in devices with current flowing in-plane and applied it to investigate with sub-ns resolution the switching dynamics of ferrimagnetic dots induced by spin-orbit torques (SOTs)

Summary

Introduction

Measurements of the transverse Hall resistance are widely used to investigate electron transport, magnetization phenomena, and topological quantum states. Measurements of the transverse resistance provide insight into magnetoresistive phenomena, such as the planar Hall effect and spin Hall magnetoresistance, which can be used to track the response of antiferromagnets and magnetic insulators to applied magnetic fields, currents, and heat[20,21,22] Extending these measurements to the time domain would enable access to the dynamics of a vast range of electronic and magnetic systems. The ns-long pulses do generate the perturbation on the magnetization, and serve as the tool for tracking the magnetic response, including single-shot switching events This capability opens up the possibility of performing systematic time-resolved Hall measurements of current-induced excitations in a broad variety of planar devices and provides access to stochastic events. Our measurements further show that the domain nucleation time can be substantially reduced by increasing the current amplitude, leading to a minimum of the critical switching energy for pulses of reduced length

Methods

Results

Conclusion