AbstractMagnetic imaging is an increasingly important tool for fundamental research and technology. The nitrogen-vacancy centre (NV) defect in diamond has emerged as a promising single-spin sensor which can detect not only magnetic fields but also electric fields and temperature. 2D mapping of magnetic fields can be achieved by grafting a diamond containing NVs to the tip of a scanning probe. Its single spin nature can be used to image large spin textures without perturbing them, as well as enabling the sensing of the stray fields produced by single electron spins and nuclear species.
Despite the realisation of NV magnetic sensing in the last few years, the technique has been developed only by few research groups. The technical challenges increase when the system is operated at cryogenic temperatures, which are needed when magnetic samples with low Curie temperature or superconductors are to be imaged. This thesis describes the work done towards the implementation of two scanning NV magnetometry experiments, the first of their kind at the University of Cambridge.
The first type of NV sensing we explore is based on NVs in nanodiamonds, deposited on the surface of a material which is ferromagnetic below 130 K. The NVs act as point-probes of the stray field, providing information on the spatial variation of the material. However, NV centres operated as point probes of stray fields are not suitable to image spin textures in magnetic materials. Starting from two types of scanning probe microscopes, one operating at room temperature and one operating from room temperature to 3 K, two scanning NV magnetometers are developed.
The imaging of the stray fields arising from magnetic field sources at the nanoscale with these two systems successfully establishes the technique in the Cavendish laboratory, offering a promising platform for the study of spin textures.
|Date of Award||12 May 2020|
|Supervisor||John G Rarity (Supervisor)|