The elementary excitations of magnets are called spin waves, and their corresponding quasi-particles are known as magnons. The rapidly growing field of Magnonics aims at using them as information... Show moreThe elementary excitations of magnets are called spin waves, and their corresponding quasi-particles are known as magnons. The rapidly growing field of Magnonics aims at using them as information carriers in a new generation of electronic devices, (almost) free of electric currents. Encoding information in the amplitude and/or phase of these coherent waves could lead to a drastic decrease in dissipated power, typically related to the motion of electrons ("Joule" or "Ohmic" heating).This dissertation describes the development and use of a new technique to study spin waves. This technique uses the electronic spins associated with nitrogen-vacancy (NV) centers as magnetic field sensors. An NV center is a light-emitting defect in the crystal lattice of diamond. Remarkably, the brightness of its emission depends on its spin state, sensitive to magnetic fields. This way, magnetic information can be investigated optically. Show less
In this thesis, I studied the origin and evolution of the non-thermal radiation in merging galaxy clusters. Cluster mergers are the among the most energetic events in the Universe. Part of this... Show moreIn this thesis, I studied the origin and evolution of the non-thermal radiation in merging galaxy clusters. Cluster mergers are the among the most energetic events in the Universe. Part of this energy is released in turbulence and shock waves which can (re-)accelerate cosmic rays and amplify magnetic fields in the intra-cluster medium (ICM). The interaction of these results in large-scale synchrotron radiation, which is visible through radio observations. In addition, X-ray observations of the ICM were carried out to investigate the dynamical state of the clusters, and the properties of cluster shocks. Show less
