Spin moments,orbital moments and magnetic anisotropy of finite-length Cowires deposited on Pd(110)

Abstract

The ground-state spin moments ⟨Sz⟩, orbitalmoments ⟨Lz⟩ and magnetic anisotropyenergy (MAE) of CoN one-dimensional (1D) clusters(N ⩽ 12) deposited on the Pd(110) surface are determined inthe framework of a self-consistent, real-space tight-bindingmethod. Remarkably large total magnetic moments per Co atom,Mz = (2⟨Sz⟩ + ⟨Lz⟩)/N = 2.8-2.9 µB, are obtained, which canbe understood as the result of three physically distincteffects. The first and leading contribution is given by thelocal spin moments ⟨Siz⟩ at the Co atomsi = 1, N (2⟨Siz⟩Co ≃ 1.6 µB). Second, significant spin moments are induced at the Pd atoms i > N close to the Co-Pd interface, which amount to about 25%of Mz (2⟨Siz⟩Pd = 0.2-0.3 µB). Finally, enhanced orbitalmagnetic moments ⟨Liz⟩ are responsible forapproximately 20% of Mz. In the case of the Co atoms,⟨Liz⟩Co = 0.28-0.33 µBis almost a factor of three larger than the Co bulk orbital moment,while in Pd atoms ⟨Liz⟩Pd = 0.05 µBrepresents about 15% of the total local moment µiz = 2⟨Siz⟩ + ⟨Liz⟩. These resultsand the associated MAEs are analysed from a local perspective.The role of the cluster-surface interactions is discussed bycomparison with the corresponding results for free-standingwires. Particularly in the case of monatomic 1D Co chains weobserve that the lowest-energy magnetization direction (easyaxis) changes from in line to off plane upon deposition onPd(110). Wire-substrate hybridizations are therefore crucialfor the magneto-anisotropic behaviour of 1D magneticnanostructures on metallic substrates.