Pinhole defects in Fe/Cr trilayers

Abstract The distribution of magnetic moments in Fe/Cr/Fe sandwiches with pinhole defects has been studied using a model Hamiltonian approach. Self-consistent calculations were performed in the Hartree-Fock approximation for ideal smooth and rough interfaces generated by a special algorithm. For a sandwich structure of Fe antiferromagnetically coupled across a Cr spacer, the pinhole defects induce a non-zero magnetisation at zero external magnetic field. The value of the total magnetic moment appears, however, to be relatively small due to the effects of frustration which take place in the system. Fe atoms inside pinholes show different magnetic moments dependent on the number of Fe atoms among its nearest neighbours. The atoms at the border of the pinholes have magnetic moment smaller than the bulk value whereas moments of inner atoms are higher than in the bulk. The role of interface roughness and pinhole defects on the stability of these magnetic states has been investigated trough total-energy calculations.