The magnetic anisotropy energy (MAE) of $3d$ transition-metal wires is calculated self-consistently as a function of length, width, structure, and $d$-band filling. One-dimensional infinite chains show MAE's which are an order of magnitude larger than in two-dimensional thin films. A further enhancement is often obtained by reducing the chain length $l$ ( $l\le 20$ atoms). The MAE of multichains (ladders) oscillates as a function of chain width and depends strongly on the transversal structure. The easy axis of Co wires changes from in-line to off-plane after deposition on Pd(110). Ladders and deposited chains show important in-plane anisotropies.

• Received 20 October 1997

DOI:https://doi.org/10.1103/PhysRevLett.81.208