Microstructures and Soft Magnetic Properties of High Saturation Magnetization Fe-Co-N alloy Thin Films

High saturation magnetization soft magnetic materials are required for future high-density recording heads as well as high frequency inductors. In this work, (Fe0.7Co0.3)1-xNx (or in short FeCoN) alloy films were synthesized with a high saturation magnetization of 24.5 kG, a hard axis coercivity of 5 Oe, an easy axis coercivity of 18 Oe, and a resistivity of 55 µΩ⋅cm. The FeCoN film sandwiched between two permalloy layers (5 nm) shows very good magnetic softness, a low hard axis coercivity of 0.6 Oe, an easy axis coercivity of 7.8 Oe, an excellent in-plane uniaxial anisotropy with an anisotropy of about 20 Oe, an initial permeability of 1000, and a roll-off frequency of 1.5 GHz. In order to understand the effect of the permalloy layers on the FeCoN layer, we fabricated four film structures: single layer FeCoN film; FeCoN film sandwiched between two permalloy layers on both sides; FeCoN film with one permalloy layer as the underlayer; and FeCoN film with one permalloy layer as caplayer. All these film structures were both magnetically and structurally characterized and compared. Structural characterization shows that there is no significant difference in the grain size of the FeCoN single layer and the FeCoN layer sandwiched between two permalloy layers. The four film structures have almost the same amount of compressive stress, about-300 MPa; and their saturation magnetostriction constants are also very close, in the range of 39.6×10-6 to 44.3×10-6. Difference in the crystallographic textures was observed in the pole figures for the FeCoN single layer and FeCoN film with permalloy underlayer