Magnetization "Steps" on a Kagome Lattice in Volborthite

TL;DR

This study investigates the magnetic behavior of volborthite, a kagome-like compound, revealing persistent spin fluctuations, exotic ordering, and multiple magnetization steps indicative of complex quantum states under magnetic fields.

Contribution

It provides new experimental evidence of quantum states and magnetization steps in volborthite, a kagome lattice compound, highlighting exotic magnetic phenomena at very low temperatures.

Findings

Persistent spin fluctuations down to 60 mK.

Observation of three magnetization steps under magnetic field.

Detection of exotic order via 51V NMR relaxation peak.

Abstract

Magnetic properties of the spin-1/2 kagome-like compound volborthite are studied using a high-quality polycrystalline sample. It is evidenced from magnetization and specific heat measurements that the spins on the kagome lattice still fluctuate at low temperature, down to T = 60 mK that corresponds to 1/1500 of the nearest-neighbor antiferromagnetic interaction, exhibiting neither a conventional long-range order nor a spin gap. In contrast, 51V NMR experiments revealed a sharp peak at 1 K in relaxation rate, which indicates that a certain exotic order occurs. Surprisingly, we have observed three "steps" in magnetization as a function of magnetic field, suggesting that at least four liquid-like or other quantum states exist under magnetic fields.