Synergistic regulation of magnetic and electrical properties in FeCoNiB soft magnetic films through B induced amorphization and Fe/Co/Ni compositional engineering

Achieving high saturation magnetization (Ms), low coercivity (Hc), and high electrical resistivity (ρ) is a key objective for soft magnetic thin films, yet conventional nonmagnetic doping often causes substantial magnetic dilution and reduces Ms. In this work, FeCoNiB soft magnetic thin films were fabricated by magnetron co-sputtering. Structural disorder was controlled by varying the B target sputtering power, while the Fe/Co/Ni ratio was further optimized to regulate magnetic and electrical properties. B incorporation suppresses long-range ordering in the FeCoNi lattice through atomic-size mismatch and chemical disorder, driving a transition from BCC crystallinity to a predominantly amorphous structure and refining the film morphology. As the B sputtering power increases, Hc decreases from 56.59 to 1.34 Oe while Ms remains above 1566 emu/cm 3 , and ρ increases from 44.4 to 104 μΩ cm due to enhanced electron scattering. In situ MOKE observations reveal that B induced amorphization changes magnetization reversal from multidomain nucleation and restricted domain wall motion to low-field reversal dominated by large-scale domain wall propagation. Further Fe/Co/Ni optimization confirms the applicability of this strategy, with Fe 30 Co 55 Ni 15 B achieving Ms = 1551.3 emu/cm 3 and Hc = 0.96 Oe. This work reveals the synergistic effects of B induced structural regulation and Fe/Co/Ni compositional optimization, providing an effective strategy for designing high-performance soft magnetic thin films for integrated magnetic applications.