Phase pure rhombohedral R3¯m$R\bar{3}m$ AgCoO₂ delafossite: Rietveld, selected area electron diffraction, X‐ray photoemission spectroscopy, and magnetic studies

Abstract

A p‐type rhombohedral AgCoO2 (S.G. Rtrue3¯m$R\bar 3m$) reported to form only at pressures greater than 300 MPa at 773 K, is stabilized in pure phase at 0.2 MPa oxygen pressure. Analysis of powder X‐ray diffraction pattern by Rietveld and selected area electron diffraction patterns confirms the purity of rhombohedral phase. Core‐shell X‐ray photoemission spectroscopy studies show that Ag ions are in +1 oxidation state with Co ions largely in +3 state. AgCoO2 is paramagnetic undergoing super‐paramagnetic transition at 44 K. The magnetic moment of Co is 0.001 μB which corresponds to low spin (LS) Co3+ along with a small fraction of LS Co4+ ions.