Ferromagnetism in 4d (Tc, Ru, Rh, Pd) and 5d (Ir, Pt) transition-metal monolayers on a Cu(001) substrate

We have studied the magnetic activity of transition metal monolayers of the 4d (Tc, Ru, Rh, Pd) and 5d (Ir, Pt) series on a Cu(001) substrate. Rh and Ir monolayers present ferromagnetism with magnetic moments 0.52 and 0.17 Bohr magnetons, respectively. We find that the Tc, Ru, Pd, and Pt monolayers are nonmagnetic. A Ru monolayer is magnetic on Ag(001) and Au(001) substrates with a comparatively high magnetic moment of 1.73 Bohr magnetons in both cases. The loss of its magnetic moment appears to be mainly due to the influence of inward tension. Cu has a smaller lattice constant than any of the monolayers considered here and therefore we are looking at the opposite effect as compared to Ag or Au. If we artificially enhance the Cu lattice constant we recover the high magnetic moment of Ru/Ag(001). We make use of the surface Green’s function matching method together with tight-binding Hamiltonians to calculate the paramagnetic local density of states projected onto the monolayer or the substrate atomic layers and calculate the magnetic moment from the minimum of the total energy as a function of the magnetic band splitting. We obtain good agreement with the known results for the same set of monolayers on Ag(001) and Au(001) substrates.