NiFe

NiFe refers to nickel–iron alloys, a family of soft magnetic materials widely used for their favorable magnetic properties. The best-known member is permalloy, Ni80Fe20, but the term also covers other compositions with varying nickel content that are designed to tailor permeability, coercivity, and magnetostriction for specific applications.

The nickel–iron system forms a complete solid solution with a face-centered cubic lattice across compositions. Permalloy and related NiFe alloys typically exhibit very low magnetostriction, especially near certain nickel concentrations, which helps minimize noise and distortion in magnetic circuits. They also offer high magnetic permeability and very low coercivity, enabling easy magnetization and demagnetization. Saturation flux density is moderate, typically around 1 tesla, which is suitable for core and shielding applications.

Processing and treatment play a crucial role in their properties. NiFe alloys are produced by melting and alloying, then cold-working and annealing to optimize grain structure and relieve internal stresses. Annealing in hydrogen, vacuum, or in the presence of controlled magnetic fields can markedly increase permeability and set magnetic anisotropy for specific device roles.

Applications for NiFe alloys are broad in magnetics. They are commonly used in transformer and inductor cores, magnetic shielding materials, and read/write heads in data storage technologies. Thin-film NiFe layers are also employed in magnetic sensors and various magneto-electronic devices, where controlled magnetic response is essential.

Variants and examples include permalloy (Ni80Fe20) as the standard reference alloy, mu-metal and related high-permeability NiFe materials for shielding, and special-purpose alloys such as Supermalloy, which achieve very high permeability through additive elements.