Initial focus in this project has been on our abilities to build the atomic scale components needed for our experiments. While previous experiments in this field were often limited in size due to material constraints, we have developed a new preparation technique that allows us to build arrays that may extend, in principle, to hundreds of nanometres in size.
Next, we developed the magnon detector. We diverted from the original design by adding a ‘counter balance’ lead to cancel the effective magnetic field due to the input lead. As a result, the detector became symmetric: it had no intrinsic preference for either of the two magnetization states, making it optimally sensitive to incoming magnons. The counter balance could also be used as a ‘reset button’, allowing the experiment to be re-initialized after the detector had sprung.
Apart from the magnon detector, we also focused on the physics of the magnetic atoms used. In particular, we studied the behavior of individual iron atoms positioned in specific high-symmetry locations on our crystal surface. We discovered that, upon sending a current through the atoms, in addition to well-known spin excitations a new excitation emerged at relatively high energy. After analysis and comparison to theoretical modelling, we managed to identify this excitation as a complete reversal of the atom’s orbital angular momentum. At first it was surprising that a single electron could cause such a big change in angular momentum. Eventually, this could be explained though in terms of the so-called Einstein – de Haas effect.
