From the bulk to monatomic wires:: An ab initio study of magnetism in Co systems with various dimensionality -: art. no. 140407

A systematic ab initio study within the framework of the local-spin-density approximation including spin-orbit coupling and an orbital-polarization term is performed for the spin and orbital moments and for the x-ray magnetic circular dichroism (XMCD) spectra in hcp Co, in a Pt supported and a free standing Co monolayer, and in a Pt supported and a free standing monatomic Co wire. When including the orbital-polarization term, the orbital moments increase drastically when going to lower dimensionality, and there is an increasing asymmetry between the L-2 and L-3 XMCD signals. It is shown that spin and orbital moments can be obtained with good accuracy from the XMCD spectra via the sum rules. The <T-z> term of the spin sum rule is surprisingly small for the wires, and the reason for this is discussed.