Recording experiments on rare-earth transition-metal thin films are studied with Lorentz microscopy

Domains written thermomagnetically under recording conditions in rare-earth transition-metal thin films are studied with Lorentz microscopy. A novel technique in which the magnetooptical layer is deposited on specially prepared silicon wafer disks provided with Si₃N₄ windows is described. This technique allows direct observation of the written domain patterns in the electron microscope. It is demonstrated that the nucleation process plays a crucial role when writing in TbFeCo. Different compositions having different temperature dependences of the magnetic properties lead to markedly different domain-formation behavior. With the detailed insight into the shape and structure of domains obtained by Lorentz microscopy, carrier and noise levels obtained from recording experiments can be understood. This is demonstrated with data on GdTbFe. It is shown that magnetic-field modulation, apart from the advantage of direct overwrite, offers the possibility of very-high-density recording