Structure and magnetism of Tm atoms and monolayers on W(110)

Abstract

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. The equilibrium structure of Tm monolayer films is found to be a strongly distorted hexagonal lattice with a Moiré 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,J z = ±5 electronic ground state separated by a few meV from the next lowest substates |J = 6,J z = ±4 and |J = 6,J z = ±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.

4f occupancy and magnetism of rare-earth atoms adsorbed on metal substrates

“…1) are in very good agreement with the spectra simulated for the 4f 11 configuration as well as with previous reports for trivalent Er [30,51]. The relative amplitudes of the multiplet peaks within the M 5 edge vary with the substrate due to the presence of a different ligand environment.…”

“…Cu (111) Ag (100) Ag (111) Pt (111) Cu (111) Ag (100) Ag ( becomes comparable to E f d + δE c and both divalent and trivalent states have been observed [11,14,17,18]. Table II summarizes the values of E f d + δE c [20,21,36], and the trends in the 4f occupation for surface adsorption.…”

“…For lower coordinated atoms, such as the ones at surfaces [31][32][33][34], in thin films [35], in small clusters [19,36], as well as in surface-adsorbed atoms, the 4f occupancy is expected to be different than for bulk. Multiple examples of trivalent states of different REs have been reported for surface-supported low coordinated atoms [11,14,16,17]. As for the divalent state, only Dy atoms on graphene/Ir(111) have been reported so far [18].…”

“…Starting with the discovery of giant magnetic anisotropy energy (MAE) in single Co atoms on Pt(111) [1], the understanding of the magnetism of single adatoms has evolved rapidly. The most studied elements having been transition metals (TM) [2][3][4][5][6][7][8][9][10], the attention is now moving to rare-earth (RE) elements [11][12][13][14][15][16], culminating in the discovery of magnetic stability in single Ho atoms on MgO(100) thin films [17] and in single Dy atoms on graphene on Ir(111) [18].…”

Antiferromagnetic Spin Coupling between Rare Earth Adatoms and Iron Islands Probed by Spin-Polarized Tunneling

“…This is what has fostered the research in single ion RE molecular magnets over the last years 19 . However, for RE adatoms on surfaces, excepting the case of Ce, which attracted some early interest associated with Kondo effect 20 21 22 , only few other lanthanides: Gd 23 24 , Ho 25 and Tm 26 have been recently investigated by using local probe techniques, on occasion combined with X-ray spectroscopy experiments 26 27 . Nevertheless, the role of 4f electrons in the tunneling process has not been thoroughly investigated, and the accessibility of these inner electrons, recently addressed in RE molecular magnets 28 , remains an open issue for the case of RE adatoms on metals 23 25 .…”