Field-Induced Magnetic Ordering in the Quantum Spin System KCuCl$_3$

TL;DR

This study investigates the magnetic behavior of KCuCl₃ under high magnetic fields, revealing field-induced magnetic ordering consistent with magnon Bose-Einstein condensation, and highlights the importance of renormalization effects in magnetic excitations.

Contribution

The paper provides detailed high-field magnetization measurements of KCuCl₃ and demonstrates the field-induced magnetic ordering consistent with magnon BEC, emphasizing renormalization effects in magnetic excitations.

Findings

Magnetization curve obtained up to 60 T at 1.3 K.

Field-induced magnetic ordering observed with a phase boundary following a power law.

Results support the magnon Bose-Einstein condensation model.

Abstract

KCuCl$_3$ is a three-dimensional coupled spin-dimer system and has a singlet ground state with an excitation gap ${\Delta}/k_{\rm B}=31$ K. High-field magnetization measurements for KCuCl$_3$ have been performed in static magnetic fields of up to 30 T and in pulsed magnetic fields of up to 60 T. The entire magnetization curve including the saturation region was obtained at $T=1.3$ K. From the analysis of the magnetization curve, it was found that the exchange parameters determined from the dispersion relations of the magnetic excitations should be reduced, which suggests the importance of the renormalization effect in the magnetic excitations. The field-induced magnetic ordering accompanied by the cusplike minimum of the magnetization was observed as in the isomorphous compound TlCuCl$_3$. The phase boundary was almost independent of the field direction, and is represented by the power law. These results are consistent with the magnon Bose-Einstein condensation picture for field-induced magnetic ordering.