Structure and Magnetic Properties of Thin Permalloy Films Near the “Transcritical” State

Various series of permalloy thin films were grown by dc-sputtering on Si (100) and glass substrates at room temperature and different argon pressure values using a Fe₂₀ Ni₈₀ target. The increase of argon pressure leads to a decrease of the Fe concentration in the films from 17 at.% to 15 at.%, an increase of the root mean square roughness of film surfaces, and a decrease of the sharpness of the crystalline texture of the samples. The increase of the film thickness leads to an increase of the coercive field. The transition to the "transcritical" state was observed at a critical thickness that decreases from 220 to 50 nm as the argon pressure in the chamber increases. This state was confirmed by the characteristic shapes of hysteresis loops, rotatable magnetic anisotropy, and the appearance of stripe domains.