Abstract
e pattern due to the overlap with the rectangular W(110) substrate. Monolayer as well as isolated Tm adatoms on W present a trivalent ground-state electronic configuration, contrary to divalent gas phase Tm and weakly coordinated atoms in quench-condensed Tm films. Ligand field multiplet simulations of the x-ray absorption spectra further show that Tm has a |J = 6,Jz =± 5� electronic ground state separated by a few meV from the next lowest substates |J = 6,Jz =± 4� and |J = 6,Jz =± 6� . Accordingly, both the Tm atoms and monolayer films exhibit large spin and orbital moments with out-of-plane uniaxial magnetic anisotropy. X-ray magnetic dichroism measurements as a function of temperature show that the Tm monolayers develop antiferromagnetic correlations at about 50 K. The triangular structure of the Tm lattice suggests the presence of significant magnetic frustration in this system, which may lead to either a noncollinear staggered spin structure or intrinsic disorder.
Highlights
Interest in low-dimensional rare-earth (RE) magnetic structures has grown steadily in recent years, focusing on single atoms as model quantum spin systems [1,2,3,4,5] as well as ultrathin films that display either ferromagnetic [6,7,8,9] or antiferromagnetic [10] order when grown on nonmagnetic substrates
We investigated the growth and magnetic properties of Tm atoms and monolayers deposited on a W(110) surface using scanning tunneling microscopy and x-ray magnetic circular and linear dichroism
Ligand field multiplet simulations of the x-ray absorption spectra further show that Tm has a |J = 6,Jz = ±5 electronic ground state separated by a few meV from the lowest substates |J = 6,Jz = ±4 and |J = 6,Jz = ±6
Summary
Interest in low-dimensional rare-earth (RE) magnetic structures has grown steadily in recent years, focusing on single atoms as model quantum spin systems [1,2,3,4,5] as well as ultrathin films that display either ferromagnetic [6,7,8,9] or antiferromagnetic [10] order when grown on nonmagnetic substrates. The extended 5d6s valence electron states of the RE atoms, on the other hand, couple with the partially filled 4f orbitals and hybridize with the surface valence electrons of the substrate This affects the exchange interaction and, the type of magnetic order and transition temperatures in ML structures [16,17,18]. Gd is the RE element that has been more extensively studied in the form of ultrathin films, mostly because it exhibits a single ferromagnetic phase in the bulk with the order transition close to room temperature [7,39,40]. Below the critical temperature, bulk RE metals display magnetically ordered phases of different complexity, depending on the element and on the temperature range [43]. We investigate the growth and magnetic properties of Tm adatoms and ML films deposited on a single-crystal W(110) surface
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