Heat capacity of the quantum magnet TiOCl

TL;DR

This study measures the heat capacity of the quantum magnet TiOCl across a broad temperature range, revealing two phase transitions with small entropy changes, indicating strong fluctuations and minimal magnetic field effects.

Contribution

It provides detailed heat capacity data for TiOCl, identifying two phase transitions and analyzing their nature and entropy changes, which was not previously characterized in detail.

Findings

Two phase transitions at 91K and 67K identified.

Small entropy change (~0.1R) suggests strong fluctuations.

No significant magnetic field dependence observed.

Abstract

Measurements of the heat capacity C(T,H) of the one-dimensional quantum magnet TiOCl are presented for temperatures 2K < T < 300K and magnetic fields up to 5T. Distinct anomalies at 91K and 67K signal two subsequent phase transitions. The lower of these transitions clearly is of first order and seems to be related to the spin degrees of freedom. The transition at 92K probably involves the lattice and/or orbital moments. A detailed analysis of the data reveals that the entropy change through both transitions is surprisingly small (~ 0.1R), pointing to the existence strong fluctuations well into the non-ordered high-temperature phase. No significant magnetic field dependence was detected.