Mapping AC Susceptibility with Quantum Diamond Microscope

TL;DR

This paper introduces a new method using nitrogen-vacancy centers in diamond combined with lock-in camera technology to map the microscale AC susceptibility of magnetic materials with high spatial resolution.

Contribution

The authors develop a novel technique that enables rapid, high-resolution imaging of AC susceptibility at the microscale using quantum diamond sensors and advanced detection methods.

Findings

Achieved AC susceptibility measurements of permalloy micro-magnets at 20 Hz

Demonstrated spatial resolution of 1.2 micrometers

Established a versatile approach for magnetic material analysis

Abstract

We present a novel technique for determining the microscale AC susceptibility of magnetic materials. We use magnetic field sensing properties of nitrogen-vacancy (\ce{NV-}) centers in diamond to gather quantitative data about the magnetic state of the magnetic material under investigation. In order to achieve the requisite speed in imaging, a lock-in camera is used to perform pixel-by-pixel lock-in detection of \ce{NV-} photo-luminescence. In addition, a secondary sensor is employed to isolate the effect of the excitation field from fields arising from magnetic structures on \ce{NV-} centers. We demonstrate our experimental technique by measuring the AC susceptibility of soft permalloy micro-magnets at excitation frequencies of up to \SI{20}{\hertz} with a spatial resolution of \SI{1.2}{\micro \meter} and a field of view of \SI{100}{\um}. Our work paves the way for microscopic measurement of AC susceptibilities of magnetic materials relevant to physical, biological, and material sciences.