Resonant Photoemission Spectroscopy of Layered Triangular Lattices Ag₂MO₂ (M = Ni and Mn): Evidence for M 3d States at Fermi Level

Partially disordered spin structure in Ag2CrO2studied withμ+SR

“…Although the [Ag 2 ] plane is thought to be responsible for the metallic conductivity, recent soft x-ray photoemission and absorption spectroscopy measurements on Ag 2 NiO 2 and Ag 2 MnO 2 revealed a contribution from the 3d electrons of Ni and Mn on the density of states at the Fermi level (E F ). 4 This is consistent with the mass enhancement of carriers below T N . 2 Furthermore, such hybridized Ni and Mn 3d states at E F would enhance the magnetic correlations between the adjacent MO 2 planes through the superexchange interaction via an M-O-(Ag 2 )-O-M pathway.…”

“…39 On the contrary, such charge disproportionation is not observed for Ag 2 NiO 2 , 5 probably due to a metallic nature of the [Ag 2 ] + plane and a hybridization between 3d and 5s orbitals. 4 This arises the special interest on the magnetic ground state of Ag 2 MO 2 , which we have attempted to elucidate with both muons and neutrons.…”

“…10 A sudden decrease of the electrical resistivity at T N suggests a strong hybridization of Cr 3d with Ag 5s orbital, 9 as found for Ag 2 NiO 2 . 4 The presence of long-range AF order is, hence, expected through the 3D interaction via the Cr-O-(Ag 2 )-O-Cr pathways. In fact, several magnetic Bragg peaks were observed below T N by ND 10 and the proposed magnetic structure was a partial disordered AF (PDA) state with 5 × 5 unit cells in the ab plane.…”

Static and dynamic spin properties in the quantum triangular lattice antiferromagnet Ag2CoO2

“…The γ values of Cr, Mn, and Ni are 9.74, 20.6, and 18.8 mJ/molK 2 , respectively. The electronic state of each compound is the d 3 HS with S = 3/2 for Cr 3+ , d 4 HS with S = 4 for Mn 3+ , and d 7 LS with S = 1/2 for Ni 3+ ; in the case of Mn, Mn 3+ was confirmed by magnetic susceptibility, whereas Mn 2.7+ was proposed by the resonant PES [26]. Extracting some information from these electronic trend should be a key to understand the origin of the enhancement of Ag 2 MO 2 system.…”

Multistep soft chemistry method for valence reduction in transition metal oxides with triangular (CdI2-type) layers

“…Even in layered Ag 2 NiO 2 , where the presence of Ag 1+ and Ni 2+ can be expected based on chemical intuition, XANES and XPS measurements confirm that subvalent silver [Ag 2 ] 1+ units coexist with Ni 3+ ions. 13,14 As seen in Fig. 1, the M 2+/3+ area for layered AMO 2 compounds is a large, empty space due to lack of materials with M 2+/3+ O 2 triangular layers.…”