Microscopic Behaviors of Magnetic Domain Walls in Co-Fe Alloy and Co-Gd Eutectic

Abstract

Direct observation of the movement of magnetic domain walls in Co–50% Fe alloy containing dislocations and in Co–18.2%m Gd alloy with eutectic structure has been studied by means of Lorentz electron microscopy. Dislocations in the alloy and second phases in the eutectic influenced directly the microscopic movements of domain walls under small external magnetic field. The domain wall behaved irreversibly at the pinning points of dislocations and second phases when the magnetic field was applied in the reverse direction. The strength of external fields to release magnetic domain walls from pinning sites was estimated from theory and compared with the experimental results. The estimated strength of the extra field is 104 Oe to release magnetic domain walls at the pinning sites of Co rods in the Co17Gd2 matrix. This result is in good agreement with the observed coercive force of the Co–18.2% Gd alloy.