(color online) (a) Schematics of the demagnetization process of thin films with different Ta thickness. (b) dM as a function of the thickness of Ta spacer layer in Ti (20 nm)/NdFeB (100 nm)Nd (10 nm)/Ta (x nm)/Fe (10 nm)/Ti (20 nm) films (x = 0–400). The inset shows the magnetization curve for 10 nm of the Fe layer. (c) Schematic of the estimation of coupling energy. (d) Coupling energy r as a function of the thickness of Ta spacer layer along the OOP direction.^[25]