Two Types of Topological Kosterlitz–Thouless Phase Transitions in SmMnO3+δ Manganites, Driven by External Magnetic Field

Abstract

It is shown that, in a SmMnO 3  sample cooled in a magnetic field H  0 to 4.2 K, the topological order–disorder phase transition of the spin system occurs within the framework of the Kosterlitz–Thouless XY -model decoupling of pairs of the flat 2 D vortices. At the same time, when the sample is cooled in the field H  0, the transition of the system of spins to a disordered state with increasing temperature occurs in the form of dissociation of pairs of bounded Z 2 vortices at the same critical temperature T KT  12 K, which is accompanied by a giant jump in the supermagnetiza-tion of the sample. The excitation and decay of low-energy bosons in a 1 D metallic Luttinger liquid at temperatures of 0.5 K and 4.2 K during sample remagnetization in the ZFC and FC measurement modes is also studied