Imaging weak magnetic fields at the nanoscale is a challenge for many field of reasearch, and for a wide range of applications, such as in material science, for the magnetic storage of the information, or in quantum optics with the opportunity to control a single spin used as a quantum bit, or in biophysics where magnetic resonance can enable structural imaging of a protein. In that context, this thesis describes the realisation of a scanning probe magnetometer based on the electron spin resonance of a single NV colour centre in diamond. Such a magnetometer provides unprecedented properties, consisting of a sub-nanometric spatial resolution, given by the effective atomic size of the defect, combined with a high sensitivity (< 1 µT/Hz^(-1/2)), even at room temperature. Moreover magnetic field ca be measured quantitatively, with no perturbation induced, which is a major asset comparing to what can be done using the usual magnetic force microscopy technique. We will first describe the realisation of the magnetic probe, consisting of a single NV colour centre in a diamond nanocristal, grafted at the apex of an AFM tip. Properties of this magnetometer will be then characterized by imaging the stray field generated by a magnetic hard disk. Different imaging techniques will be presented, and compared during this study. Finally, magnetic vortex in patterned ferromagnetic thin film will be imaged, especially the vortex core, which is known to be one of the smallest object of micromagnetism. The exceptional properties of NV based magnetometry, demonstrated in ths work, might enable various applications in nanomagnetisms and spintronics.
