Magnetoelastic Coupling in the Spin-Dimer System TlCuCl$_3$

TL;DR

This study investigates the strong magnetoelastic coupling in TlCuCl₃, revealing how magnetic field-induced order is highly sensitive to pressure and lattice changes, with implications for tuning magnetic properties.

Contribution

It provides high-resolution measurements showing the significant impact of uniaxial pressure on magnetic phase boundaries and intradimer couplings in TlCuCl₃.

Findings

Pronounced anomalies in thermal expansion and magnetostriction signal strong magnetoelastic coupling.

Phase boundary highly sensitive to uniaxial pressure, with transition field change of about +/- 185%/GPa.

Intramolecular exchange interactions are significantly affected by uniaxial pressure, while interdimer couplings are less affected.

Abstract

We present high-resolution measurements of the thermal expansion and the magnetostriction of TlCuCl$_{3}$ which shows field-induced antiferromagnetic order. We find pronounced anomalies in the field and temperature dependence of different directions of the lattice signaling a large magnetoelastic coupling. The phase boundary is extremely sensitive to pressure, e.g. the transition field would change by about +/- 185$%/GPa under uniaxial pressure applied along certain directions. This drastic effect can unambiguously be traced back to changes of the intradimer coupling under uniaxial pressure. The interdimer couplings remain essentially unchanged under pressure, but strongly change when Tl is replaced by K.