Improving the Magnetic Properties of Molecular-Beam-Vapor-Deposited Ni₄₅Fe₅₅ Nanocrystalline Films by In-Situ High Magnetic Field Application

Nanocrystalline soft magnetic films with high saturation magnetization M_S and low coercivity H_C are needed to meet the application demands. This paper studies the effects of in-situ high magnetic field application on 80 nm thick Ni₄₅ Fe₅₅ film prepared by molecular beam vapor deposition. The results show that a 6 T magnetic field can significantly decrease H _C by 73.9% to 4.847 Oe and increase M_S by 19.6% to 1.276 × 10⁶ A/m for films deposited on a room temperature substrate. By increasing the substrate temperature to 400 °C, the soft magnetic properties of the film can also be slightly increased. However, the 6 T magnetic field effect is much more significant than that of an increased substrate temperature. This is attributed to better crystallinity, smaller grain size and a complete 111 orientation in the film induced by high magnetic field. The coercivity variations of the films agree with the results evaluated on the basis of the extended Random Anisotropy Model. The enhanced magnetic field effects on nanoparticles provide a novel approach to control film growth and its properties.