Magnetic-Field Induced Gap in One-Dimensional Antiferromagnet KCuGaF$_6$

TL;DR

This study investigates how an external magnetic field induces a gap in the excitation spectrum of the one-dimensional antiferromagnet KCuGaF$_6$, revealing a field-dependent gap growth linked to antisymmetric interactions.

Contribution

It demonstrates the magnetic-field-induced gap and susceptibility in KCuGaF$_6$, highlighting the role of Dzyaloshinsky-Moriya interactions and staggered $g$-tensor effects.

Findings

Magnetic field induces a staggered susceptibility following Curie law.

An excitation gap proportional to $H^{2/3}$ is observed.

No magnetic ordering down to 0.46 K.

Abstract

Magnetic susceptibility and specific heat measurements in magnetic fields were performed on an $S=1/2$ one-dimensional antiferromagnet KCuGaF$_6$. Exchange interaction was evaluated as $J/k_{\rm B}\simeq 100$ K. However, no magnetic ordering was observed down to 0.46 K. It was found that an applied magnetic field induces a staggered magnetic susceptibility obeying the Curie law and an excitation gap, both of which should be attributed to the antisymmetric interaction of the Dzyaloshinsky-Moriya type and/or the staggered $g$-tensor. With increasing magnetic field $H$, the gap increases almost in proportion to $H^{2/3}$.