Magnetization Plateaus in the Spin-1/2 Kagome Antiferromagnets: Volborthite and Vesignieite

TL;DR

This study measures magnetization in volborthite and vesignieite, revealing a common high-field plateau near 0.40Ms, which exceeds theoretical predictions and suggests a shared origin with magnetization steps.

Contribution

It provides experimental evidence of high-field magnetization plateaus in kagome antiferromagnets, challenging existing theoretical models and indicating a common underlying mechanism.

Findings

Magnetization plateau near 0.40Ms observed in both compounds

Magnetizations exceed the predicted Ms/3 plateau value

Excess magnetization correlates with magnetization steps

Abstract

The magnetization of two spin-1/2 kagome antiferromagnets, volborthite and vesignieite, has been measured in pulsed magnetic fields up to 68 T. A magnetization plateau is observed for each compound near the highest magnetic field. Magnetizations at saturation are approximately equal to 0.40Ms for both compounds, where Ms is the fully saturated magnetization, irrespective of a difference in the distortion of the kagome lattice between the two compounds. It should be noted that these values of magnetizations are significantly larger than Ms/3 predicted theoretically for the one-third magnetization plateau in the spin-1/2 kagome antiferromagnet. The excess magnetization over Ms/3 is nearly equal to the sum of the magnetizations gained at the second and third magnetization steps in volborthite, suggesting that there is a common origin for the excess magnetization and the magnetization steps.