New applications of nitrogen-vacancy centers in diamond

Abstract

Magnetometry is widely used industry, science and everyday life. Applications include navigation, geology, chemical analysis and magnetic resonance imaging (MRI), among many others. The different types of magnetic-field sensors, depending on the application, may differ in sensitivity, bandwidth, operational conditions (e.g. temperature and pressure), spatial resolution and price. In the last two decades, a new magnetometer type based on nitrogen-vacancy (NV) color centers in diamond has gained a lot of attention. NV magnetometers are not the most sensitive compared to superconducting quantum interference devices (SQUIDs) or atomic magnetometers, but feature remarkable properties such as nanoscale resolutions and the ability to be operated from cryogenic temperatures up to ~ 700K and under pressures up to 60GPa they excel in various applications This work presents several applications and advances in sensor development that show the strengths of NV-center-based magnetometry. In particular, micron sized diamond samples which In incorporate a layer with high NVcenter density are employed to image vortices in a type-II superconductor using a wide-field configuration. Furthermore, a setup to image both magnetization of (ferro-)magnetic samples via light polarization and the generated stray magnetic field via NV magnetic imaging is designed and constructed. The functionality was demonstrated on a ferromagnetic thin film that shows stripelike domains upon change of external magnetic field. In addition to the aforementioned applications, a method to utilize (single-) NV centers at zero field was developed. This was necessary due to failure of conventional NV magnetometry protocols because of line crossings at zero field. With the use of circularly polarized microwave fields, we were able to overcome this issue and extend NV-center magnetometry to applications that require zero-field conditions, such as zero-field nuclear magnetic resonance or observation of the domain structure of magnetic samples across the full hysteresis loop.