Investigation on the intergranular interaction of the soft magnetic granular films by δ M ( H ) curves

( Fe 65 Co 35 ) x ( SiO 2 ) 1 − x granular films with various volume fraction ( x ) of Fe 65 Co 35 alloy were fabricated by magnetron sputtering, and the interaction between granules was explored by δ M ( H ) plots. Research results show that δ M ( H ) is positive for the samples in a wide range of 0.42 < x < 0.86 , indicating that exchange coupling exists among granules. Further research revels that δ M ( H ) max increases gradually with decreasing x , reaching the maximum value at x = 0.57 , then decreases after x < 0.57 . Since δ M ( H ) max can effectively reflect the intensity of exchange coupling, the intergranular exchange coupling also increases first, then decreases as x decreases. The microstructure is analyzed with help of the high-resolution transmission electron microscopy, and results show that the variation of exchange coupling with metal volume fraction x is dominated by the change of microstructure of samples. The microstructure of the sample with x = 0.57 satisfy the optimization for realizing exchange coupling, leading to excellent soft magnetic properties.