Nanocavity optomechanical torque magnetometry and radiofrequency susceptometry

TL;DR

This paper introduces a nanophotonic optomechanical device that enables highly sensitive measurements of magnetic properties and responses of nanoscale structures, advancing nanoscale magnetometry and susceptometry in ambient conditions.

Contribution

The work demonstrates a novel on-chip optomechanical magnetometer and susceptometer capable of detecting magnetic signals at the nanoscale with high sensitivity and resolution.

Findings

Able to observe Barkhausen steps in magnetic hysteresis

Detected enhanced RF susceptibility linked to vortex core hopping

Achieved magnetic moment resolution suitable for single mesoscopic structures

Abstract

Nanophotonic optomechanical devices allow observation of nanoscale vibrations with sensitivity that has dramatically advanced metrology of nanomechanical structures [1-9] and has the potential to impact studies of nanoscale physical systems in a similar manner [10, 11]. Here we demonstrate this potential with a nanophotonic optomechanical torque magnetometer and radiofrequency (RF) magnetic susceptometer. Exquisite readout sensitivity provided by a nanocavity integrated within a torsional nanomechanical resonator enables observations of the unique net magnetization and RF-driven responses of single mesoscopic magnetic structures in ambient conditions. The magnetic moment resolution is sufficient for observation of Barkhausen steps in the magnetic hysteresis of a lithographically patterned permalloy island [12]. In addition, significantly enhanced RF susceptibility is found over narrow field ranges and attributed to thermally assisted driven hopping of a magnetic vortex core between neighboring pinning sites [13]. The on-chip magneto-susceptometer scheme offers a promising path to powerful integrated cavity optomechanical devices for quantitative characterization of magnetic micro- and nanosystems in science and technology.