Remagnetization of Finite-Length Ferromagnetic Cobalt Atomic Chains

The remagnetization mechanisms of finite-length ferromagnetic cobalt atomic chains at the Pt(664) surface have been investigated. It has been found that the remagnetization of short chains occurs due to the simultaneous flipping of all magnetic moments. At longer chain lengths, remagnetization occurs through the formation of a Néel-type anti-clockwise domain wall. The remagnetization of long chains can be achieved through both the formation of anti-clockwise and clockwise domain walls. The energy barriers for remagnetization of atomic chains with lengths ranging from 5 to 100 atoms have been calculated using the geodesic nudged elastic band method. In the framework of the harmonic approximation of the transition state theory, frequency prefactors have been calculated. A non-monotonic and sufficiently strong dependence of the frequency prefactors on both the chain length and an external magnetic field has been identified. The magnetization curves of Co atomic chains have been constructed, and the residual magnetization values and coercive force of the chains have been determined. The dependences of the coercive force on the chain length, temperature, and remagnetization rate of the magnetic field have been analyzed.