Observation of a Transient Magnetization Plateau in a Quantum Antiferromagnet on the Kagome Lattice

TL;DR

This study reports the observation of a transient 1/3 magnetization plateau in a kagome lattice antiferromagnet, revealing dynamical phenomena and proposing a theoretical explanation involving order by disorder.

Contribution

First experimental detection of a transient magnetization plateau in a kagome antiferromagnet, combined with theoretical analysis of exchange interactions and dynamical effects.

Findings

Transient 1/3 magnetization plateau observed in pulsed fields

Exchange parameters J_1 and J_2 determined as -19K and 6K

Dynamical order by disorder may explain the transient plateau

Abstract

The magnetization process of an S=1/2 antiferromagnet on the kagome lattice, [Cu_3(titmb)_2(OCOCH_3)_6]H_2O {titmb= 1,3,5-tris(imidazol-1-ylmethyl)-2,4,6 trimethylbenzene} has been measured at very low temperatures in both pulsed and steady fields. We have found a new dynamical behavior in the magnetization process: a plateau at one third of the saturation magnetization appears in the pulsed field experiments for intermediate sweep rates of the magnetic field and disappears in the steady field experiments. A theoretical analysis using exact diagonalization yields J_1=-19K and J_2=6K, for the nearest neighbor and second nearest neighbor interactions, respectively. This set of exchange parameters explains the very low saturation field and the absence of the plateau in the thermodynamic equilibrium as well as the two-peak feature in the magnetic heat capacity. Supported by numerical results we argue that a dynamical order by disorder phenomenon could explain the transient appearance of the 1/3 plateau in pulsed field experiments.