Orthogonal spin arrangement as possible ground state of three - dimensional Shastry - Sutherland network in Ba3Cu3In4O12

TL;DR

This paper investigates the magnetic ground state of Ba3Cu3In4O12, revealing a unique three-dimensional orthogonal spin arrangement stabilized by anisotropic exchange interactions and quantum fluctuations, leading to an 'order by disorder' phenomenon.

Contribution

It proposes a novel orthogonal spin ground state in a 3D Shastry-Sutherland network, highlighting the role of anisotropic exchange and quantum fluctuations.

Findings

Identification of a three-dimensional orthogonal magnetic ground state.

Observation of multiple spin-flop and spin-flip transitions.

Evidence of 'order by disorder' stabilization of the ground state.

Abstract

The Ba3Cu3In4O12 stands for unique topology of the magnetic subsystem. It consists of rotated by 90\Box$^b$ relative to each other "paper-chain" columns made of vertex-sharing CuIO4 and CuIIO4 planar units. The overall pattern of the copper ions is that of a three-dimensional Shastry-Sutherland network. At high temperatures, the magnetic susceptibility follows the Curie-Weiss law with positive Weiss temperature indicating strong predominance of ferromagnetic coupling. At low temperatures, however, this compound reaches the antiferromagnetically ordered state and experiences non-trivial succession of two spin-flop and two spin-flip transitions reaching full saturation in modest magnetic fields. Here we show that the possible ground state in Ba3Cu3In4O12 can be three-dimensional orthogonal arrangement of the Cu2+ (S = 1/2) magnetic moments forming three virtually independent antiferromagnetic subsystems. In this arrangement, favored by anisotropic exchange interactions, the quantum fluctuations provide the coupling between three mutually orthogonal magnetic subsystems resulting in an impressive "order by disorder" effect.