Ni80Fe20

Ni80Fe20, commonly known as permalloy, is an iron-nickel alloy containing about 80% nickel and 20% iron by composition. It is a soft magnetic material prized for its very high magnetic permeability and extremely low coercivity, which allow it to be magnetized and demagnetized with little energy input. The alloy forms a disordered face-centered cubic solid solution at room temperature and exhibits near-zero magnetostriction, reducing mechanical stress and noise in magnetic devices.

Due to these magnetic properties, Ni80Fe20 is widely used as a core material in inductors and transformers, for magnetic shielding, and in various magnetic sensors. Thin-film versions are common in magnetoresistive devices and integrated circuits, while ribbon or foil forms serve shielding and energy storage applications. The high saturation magnetization of permalloy further supports efficient magnetic performance in these roles.

Processing typically involves annealing, often in the presence of a magnetic field, to optimize permeability and tailor magnetic anisotropy. Ni80Fe20 can be produced and shaped by standard metallurgical methods, including sputtering, vacuum deposition, electroplating, casting, and mechanical deformation. The precise magnetic behavior depends on composition, microstructure, and thermal history; deviations from the 80/20 ratio or the introduction of stress can alter permeability and coercivity.

Ni80Fe20 is a primary member of the permalloy family of Ni–Fe alloys, renowned for combining high saturation magnetization with soft magnetic behavior. Since the early 20th century, it has served as a benchmark material for magnetic devices and continues to be used in a wide range of electronic and electromagnetic applications.