Magnetostrictive Neel ordering of the spin-5/2 ladder compound BaMn2O3: distortion-induced lifting of geometrical frustration

TL;DR

BaMn2O3 exhibits Neel ordering driven by a distortion that relieves geometrical frustration in its spin ladder structure, revealing complex magnetic behavior in a low-dimensional system.

Contribution

This study uncovers the distortion-induced lifting of frustration and the resulting magnetic order in BaMn2O3, a novel realization of a spin-5/2 ladder compound.

Findings

BaMn2O3 transitions to antiferromagnetic order at 184 K.

A strong monoclinic distortion accompanies the magnetic transition.

Magnetic susceptibility confirms low-dimensional magnetic behavior.

Abstract

The crystal structure and the magnetism of BaMn$_2$O$_3$ have been studied by thermodynamic and by diffraction techniques using large single crystals and powders. BaMn$_2$O$_3$ is a realization of a $S = 5/2$ spin ladder as the magnetic interaction is dominant along 180$^\circ$ Mn-O-Mn bonds forming the legs and the rungs of a ladder. The temperature dependence of the magnetic susceptibility exhibits well-defined maxima for all directions proving the low-dimensional magnetic character in BaMn$_2$O$_3$. The susceptibility and powder neutron diffraction data, however, show that BaMn$_2$O$_3$ exhibits a transition to antiferromagnetic order at 184 K, in spite of a full frustration of the nearest-neighbor inter-ladder coupling in the orthorhombic high-temperature phase. This frustration is lifted by a remarkably strong monoclinic distortion which accompanies the magnetic transition.