Observation of laser-written magnetic domains in amorphous TbFe films by Lorentz microscopy

A review is given of Lorentz microscopy and its application to the study of laser-written domains in amorphous rare-earth/transition-metal–type materials. Domains, or regions of reverse magnetization, were written under various conditions of laser power and applied magnetic field in TbxFe1−x films where x varies in the range 0.14–0.32. Upon examination by Lorentz microscopy, and under certain conditions, these written regions show highly detailed magnetic structures. One condition for obtaining good images is the avoidance of oxidized surface layers showing in-plane magnetization. Another condition is tilting of the film plane in the transmission electron microscope to enhance image contrast. A variety of domain structures have been observed ranging from fully saturated regions with both highly regular and irregular boundaries, to fully demagnetized regions. An example of correlation between the field dependence of the microstructure and measurements of magneto-optical signal is given for the x=0.32 composition. Results are presented of carrier signal and noise measurements made on a film on a rotating disk.