Magnetic force microscopy observations of Co–Ni–Ga and Co–Ni–Al alloys with two-phase structures

This study investigated the magnetic domain morphologies of Co–Ni–Ga and Co–Ni–Al alloys with the β + γ two-phase structures by magnetic force microscopy. In the rapidly solidified state, the martensite in a grain refined Co45Ni25Ga30 alloy exhibited sharp magnetic contrast, whereas the parent phase in a Co38Ni34Al28 alloy with divorced eutectic structure had weak magnetic anisotropy. After annealing at 1173 K, the γ phase showed fulgurous magnetic domains in the annealed Co45Ni25Ga30, and stripe-like 180° domain walls in regularly eutectic Co38Ni34Al28.