In ferromagnetic materials, such as iron, cobalt, or nickel, the magnetic moments of the atoms are all ordered parallel, leading to a macroscopic net magnetization of the material. This magnetization can be reoriented between two directions at fast GHz rates, which is used to encode binary bits of information (0s and 1s) in hard disk drives (HDDs). Currently, more than half of the global digital data is stored this way. Unfortunately, the use of ferromagnets has hit its fundamental limits in terms of speed, stability, and power consumption. An alternative approach would be to use antiferromagnets, where the magnetic moments of neighbouring atoms are ordered antiparallel. These magnetic materials are more robust and up to thousands of times faster than ferromagnets. However, antiferromagnets do not immediately appear magnetic, making them notoriously difficult to control. Over the past years, it has become clear that using ultrashort pulses of light might be the fastest and most energy-efficient way to obtain control of antiferromagnets. This PhD thesis explores new methods to control the orientation of the atomic moments in antiferromagnets by creating and exploring new "coherent and non-equilibrium states" using ultrashort pulses of light.
After my double bachelor’s in Mathematics and Physics and Master’s in Physics at Radboud University, I started a PhD at Radboud University in collaboration with the Technical University of Eindhoven (TU/e) in September 2020. During my PhD, I focused on the ultrafast (nonlinear) control of antiferromagnets using intense THz-frequency light pulses using far-field (magneto-) optical methods. This research was conducted under the supervision of prof. Alexey Kimel (Radboud) and Prof. Bert Koopmans (TU/e). The work led to the discovery of various novel and sometimes unanticipated methods of controlling antiferromagnets by light.
