Magnetostructural phase transition assisted by temperature in Ag–αMnO2: a density functional theory study

Abstract

A crystalline material formed by parallel chains of silver atoms inside one-dimensional tunnels of hollandite manganese dioxide, Ag–αMnO₂, is investigated through first-principles total energy calculations. Two different magnetic phases have been identified; one structure containing linear Ag chains with an antiferromagnetic ordering in the direction perpendicular to the MnO₂ tunnels for T = 0 K (I4/m) and another configuration with zigzag Ag chains in a non-magnetic regime for higher temperatures (P2₁/c). According to phonon dispersions, both structures are stable. On the other hand, the structure with linear Ag chains in the non-magnetic state is unstable. A critical temperature of T_c ≃ 125 K for the magnetostructural phase transition between the two stable structures I4/m and P2₁/c is predicted.