Effect of Ultrathin Inserted Ag Layer on Perpendicular Magnetic Anisotropy of CoFeB Thin Film

We provide a new method to improve the perpendicular magnetic anisotropy (PMA) of CoFeB thin film by ultrathin Ag-layer insertion. Experimentally, 1 nm Ag insertion can greatly improve the ratio of Hc (out-of-plane)/H_c (in-plane) compared with the single-layer CoFeB film, indicating that stronger PMA can be achieved by 1 nm Ag insertion. Nevertheless, the strength of PMA critically depends upon the thickness of Ag insertion layer. On the contrary, 0.5 nm Ag-inserted CoFeB film cannot obtain PMA because of the failure in forming Ag/CoFeB interface and the Ag atoms´ diffusion into CoFeB layer. Theoretically, based on the first-principles, total energy calculations show that the magnetic anisotropy energy (MAE) of the 1 nm Ag-inserted CoFeB film is positive and its value is much larger than that of single-layer CoFeB film. It proves that the 1 nm Ag insertion into CoFeB film can improve the PMA because of the interfacial effect. Nevertheless, in the 0.5 nm Ag-inserted model, the MAE is much smaller than that with 1 nm Ag insertion. Our results reveal that 1 nm Ag layer insertion in CoFeB film might pave a way toward enhancing PMA in high-density magnetic memory application.