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Free keywords:
Crystals, Perovskite, Phase separation, Silver compounds, perovskite, A-site ordered quadruple perovskites, Charge/orbital order, Crystal phasis, High pressure and high temperature, Monoclinics, Orbitals, Perovskite oxides, Site charges, Spin order, Structural phase transition, article, controlled study, high temperature, hyperbaric pressure, phase separation, phase transition, room temperature, temperature, Manganese compounds
Abstract:
An AA′3B4O12-type A-site-ordered quadruple perovskite oxide AgMn7O12 was prepared by high-pressure and high-temperature methods. At room temperature, the compound crystallizes into a cubic Im3̅ symmetry with a charge distribution of AgMn33+Mn43.5+O12. With the temperature decreasing to TCO,OO ≈ 180 K, the compound undergoes a structural phase transition toward a monoclinic C2/m symmetry, giving rise to a B-site charge- and orbital-ordered AgMn33+Mn23+Mn24+O12 phase. Moreover, this charge-/orbital-ordered main phase coexists with the initial cubic AgMn33+Mn43.5+O12 phase in the wide temperature range we measured. The charge-/orbital-ordered phase shows two antiferromagnetic phase transitions near 125 and 90 K, respectively. Short-range ferromagnetic correlations are found to occur for the initial B-site mixed cubic phase around 35 K. Because of the robust phase separation, considerable magnetoresistance effects are observed below TCO,OO in AgMn7O12 © 2024 American Chemical Society.
