Dilatometry study of the ferromagnetic order in single-crystalline URhGe

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.Comment: 5 page

Magnetic phase diagrams of UNiGe

UNiGe undergoes two magnetic transitions in zero field. Here, the magnetic diagrams of UNiGe for B {parallel} b and B {parallel} c are reported. We performed temperatures scans of the magnetization in static magnetic fields up to 19.5T applied along the b and c axes. For both orientations 3 magnetic phases have been identified in the B-T diagrams. We confirmed the previously reported phase boundaries for B {parallel} c, and in addition we determined the location of the phase boundaries for B {parallel} b. We discuss a possible relationship of the two zero-field antiferromagnetic phases (commensurate: T<42K; incommensurate: 42K<T<50K) and the field-induced phase, which, at low temperatures, occurs between 18 and 25T or 4 and 10T for B {parallel} b or B {parallel} c, respectively. Finally, we discuss the field dependence of the electronic contribution {gamma} to the specific heat for B {parallel}c up to 17.5T, and we find that its field dependence is similar to the one found in more itinerant uranium compounds