Quantum paramagnets on the honeycomb lattice and field-induced N\'eel order: Possible application to Bi$_3$Mn$_4$O$_{12}$(NO$_3$)

TL;DR

This paper investigates how various exchange interactions and magnetic fields induce Néel order in a frustrated spin-3/2 honeycomb antiferromagnet, with potential relevance to experimental observations in Bi$_3$Mn$_4$O$_{12}$(NO$_3$).

Contribution

It introduces a comprehensive theoretical analysis of frustrated spin-3/2 honeycomb systems, considering multiple exchange interactions and magnetic fields, to explain field-induced Néel order.

Findings

Paramagnetic states transition to Néel order beyond a critical magnetic field.

Biquadratic exchange leads to an AKLT valence bond solid.

Bilayer coupling results in an interlayer dimer solid.

Abstract

Motivated by recent experiments on the spin-3/2 frustrated bilayer honeycomb antiferromagnet Bi$_3$Mn$_4$O$_{12}$(NO$_3$), we study the spin-S Heisenberg model on the honeycomb lattice with various additional exchange interactions which frustrate N\'eel order. Using spin wave theory, exact diagonalization, and bond operator theory, we consider the effects of (i) second-neighbor exchange, (ii) biquadratic exchange for $S = 3/2$ which leads to an AKLT valence bond solid, and (iii) bilayer coupling which leads to an interlayer dimer solid. We show that the resulting paramagnetic states undergo a transition to N\'eel order beyond a critical magnetic field. We discuss experimental implications for Bi$_3$Mn$_4$O$_{12}$(NO$_3$).