Taking Advantage of Gold’s Electronegativity in R₄Mn_3–xAu_10+x (R = Gd or Y; 0.2 ≤ x ≤ 1)

Abstract

Ternary R 4 Mn 3−x Au 10+x (R = Gd or Y; 0.2 ≤ x ≤ 1) compounds have been synthesized and characterized using single-crystal X-ray diffraction. The structure is a ternary variant of orthorhombic Zr 7 Ni 10 (oC68, space group Cmca) and is isostructural with Ca 4 In 3 Au 10 . The structure contains layers of Mn-centered rectangular prisms of gold (Mn@Au 8 ), interbonded via Au atoms in the b-c plane, and stacked in a hexagonal close packed arrangement along the a direction. These layers are bonded via additional Mn atoms along the a direction. The rare-earth metals formally act as cations and fill the rest of the space. The structure could also be described as sinusoidal layers of gold atoms, which are interconnected through Au−Au bonds. The magnetic characteristics of both compounds reveal the presence of nearly localized Mn magnetic moments. Magnetization M measurements of Y 4 Mn 2.8 Au 10.2 versus temperature T and applied magnetic field H demonstrate the dominance of antiferromagnetic (AFM) interactions in this compound and indicate the occurrence of noncollinear AFM ordering at T N1 = 70 K and a spin reorientation transition at T N2 = 48 K. For the Gd analogue Gd 4 Mn 2.8 Au 10.2 , the M(H,T) data instead indicate the dominance of ferromagnetic interactions and suggest a ferrimagnetic transition at T C ≈ 70 K for which two potential ferrimagnetic structures are suggested. Linear muffin-tin orbital calculations on the stoichiometric composition "Y 4 Mn 3 Au 10 " using the local spin density approximation indicate a ∼1 eV splitting of the Mn 3d states with nearly filled majority spin states and partially filled minority spin states at the Fermi level resulting in approximately four unpaired electrons per Mn atom in the metallic ground state. The crystal orbital Hamilton population analyses demonstrate that ∼94% of the total Hamilton populations originate from Au−Au and polar Mn−Au and Y−Au bonding.

Transition metals on the (0 0 0 1) surface of graphite: Fundamental aspects of adsorption, diffusion, and morphology

“…The bonding-induced change in electron density is mainly localized on the carbon atoms closest to the metal adatom [54,55]. Among the physisorbed metals, Au exhibits net electron transfer from the substrate to the metal adatom, in keeping with the fact that Au is a very electronegative metal [58,59].…”

“…The bonding-induced change in electron density is mainly localized on the carbon atoms closest to the metal adatom [54,55]. Among the physisorbed metals, Au exhibits net electron transfer from the substrate to the metal adatom, in keeping with the fact that Au is a very electronegative metal [58,59].As stated in Eq.(1), bonding of metal adatoms with graphite is stronger than bonding with graphene, but to first order, one expects the trends in E a noted above to be similar for graphite. The reason for the higher adsorption energies on graphite is undoubtedly related to the dispersion forces which bind the carbon sheets, as noted by Hardcastle et al[53].…”

Nucleation and growth of metals on carbon surfaces

“…The bondinginduced change in electron density is mainly localized on the carbon atoms closest to the metal adatom [53,54]. Among the physisorbed metals, Au exhibits net electron transfer from the substrate to the metal adatom, in keeping with the fact that Au is a very electronegative metal [57,58]. Ag is also exceptional, in that E a/graphene is nearly zero (0.02 eV) and there is little charge transfer, i.e.…”

CsMn4As3: A Layered Tetragonal Transition-Metal Pnictide Compound with an Antiferromagnetic Ground State

“…It may be noted that Mn 3d along with the 4s and 4p orbitals significantly participate in the chemical bonding with As and thus result in a more delocalized 3d state of Mn compared to our earlier-reported Mn-based intermetallic compounds. 28,29 Heat Capacity. Figure 4 shows the temperature T variation of the heat capacity C p of CsMn 4 As 3 .…”