Collaborative research by Dr. Charilaou in magnetic phases published in the Journal of Applied Physics

Coexistence of soft and hard magnetic phases in single layer amorphous Tb–Co thin films

In a new article published in the Journal of Applied Physics, experiments and simulations have shown that in a thin film, just a few tens of atoms thick, it is possible to have both hard and soft magnetic properties. Researchers at UC Berkeley, in collaboration with Dr. Michalis Charilaou from the Physics department at UL Lafayette, have found that amorphous Tb-Co films, i.e., where the atoms do not form a periodic lattice crystal, growth conditions can be adjusted such to create two layers in the films. As the films start to grow, the first few tens of atoms are in a low density formation, but as additional atoms are deposited on top, the structure becomes 20% denser. That, results in two magnetic systems in one structure: the low-density base is a soft magnet, whereas the high-density top is a hard magnet. At low temperature, this soft/hard bilayer exhibits a behavior known as the exchange spring, where as seen in the figure here the magnetization of the films bounces back to its original state once the field is removed, just as a spring recoils when the load is removed from it. These observations suggest that growth-induced density-differential structures have the potential to yield high-performance nanoscale exchange-spring magnets, which are promising candidates for high-density information storage devices and other nanomagnetic technologies.