Nano-granular Co-Zr-O magnetic films studied by HRTEM and electron holography

The microstructures and magnetic domain structures of nano-granular Co-Zr-O thin films (Co71.5Zr9.2O19.3, Co59.9Zr10.3O29.8 and Co52.9Zr12.0O35.1) with different magnetic properties were investigated by transmission electron microscopy. High-resolution transmission electron microscopy (HRTEM) reveals that these Co-Zr-O thin films are all composed of nano-sized Co crystal grains dispersing in the Co-Zr-O amorphous matrix. The detailed distribution of lines of magnetic flux in each specimen is clarified by electron holography. In the specimen of Co59.9Zr10.3O29.8, which has the highest magnetic anisotropy field, the existence of 180 deg. magnetic domain walls is clarified. The Co52.9Zr12.0O35.1, which has the smallest Co grain size, has reticulate domain walls or fluctuated lines of magnetic flux, suggesting the mixed state of ferromagnetic and superparamagnetic states