Magnetic and Electric Properties of Amorphous Co40Fe40B20 Thin Films

C40Fe40B20 was deposited on a glass substrate to a thickness (tf) of between 100 Å and 500 Å. X‐ray diffraction patterns (XRD) indicate that C40Fe40B20 films are in an amorphous state. The plane‐view microstructures and grain size distributions of CoFeB thin films are observed under a high‐resolution transmission electron microscope (HRTEM). The thicker CoFeB films have larger grain size distribution than thinner CoFeB films. The saturation magnetization (Ms) exhibits a size effect, meaning that Ms increases as tf increases. The magnetic remanence magnetization (Mr) of CoFeB thin films are sensitive to thinner CoFeB films, and the refined grain size of thinner CoFeB films can induce ferromagnetic stronger spin exchange‐coupling behavior than thicker CoFeB films, resulting in higher remanence. The highest magnetic squareness ratio (Mr/Ms) of the CoFeB films occurs at thickness of 100 Å, suggesting the 100 Å of the as‐deposited CoFeB film is suitable for magnetic memory application. These results also demonstrate that coercivity (Hc) is increased by an increase in the width of the distribution of grain sizes. The electrical resistivity (ρ) of such a film is typically higher than normally exceeding 100 μΩ cm, revealing that the amorphous phase dominates. These results are consistent with the XRD results.