Dilatometry study of the ferromagnetic order in single-crystalline URhGe

TL;DR

This study investigates the thermal expansion and ferromagnetic properties of single-crystalline URhGe, revealing positive pressure dependencies of the Curie temperature and enhanced spin fluctuation volume dependence at low temperatures.

Contribution

It provides new insights into the volume dependence of ferromagnetic order and spin fluctuations in URhGe through detailed dilatometry measurements.

Findings

Positive uniaxial pressure dependencies of T_C along all axes

Hydrostatic pressure increases T_C by 0.12 K/kbar

Enhanced volume dependence of ferromagnetic spin fluctuations at low temperatures

Abstract

Thermal expansion measurements have been carried out on single-crystalline URhGe in the temperature range from 2 to 200 K. At the ferromagnetic transition (Curie temperature T_C = 9.7 K), the coefficients of linear thermal expansion along the three principal orthorhombic axes all exhibit pronounced positive peaks. This implies that the uniaxial pressure dependencies of the Curie temperature, determined by the Ehrenfest relation, are all positive. Consequently, the calculated hydrostatic pressure dependence dT_C/dp is positive and amounts to 0.12 K/kbar. In addition, the effective Gruneisen parameter was determined. The low-temperature electronic Gruneisen parameter \Gamma_{sf} = 14 indicates an enhanced volume dependence of the ferromagnetic spin fluctuations at low temperatures. Moreover, the volume dependencies of the energy scales for ferromagnetic order and ferromagnetic spin fluctuations were found to be identical.