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

SUPERCONDUCTING AND MAGNETIC PROPERTIES OF ErRh4B4

Nous avons mesuré la dilatation thermique, l'aimantation, la dilatation magnétostrictive et la résistivité électrique du composé ErRh4, B4 aux basses températures. Nous présentons les résultats sur l'influence des champs magnétiques sur les propriétés supraconductrices et magnétiques et nous discutons le diagramme de phase (H,T).We have measured the thermal expansion, the magnetization, the magnetostriction and the ac electrical resistance of ErRh4B4 at low temperatures. Special emphasis is given to the influence of magnetic fields on the superconducting and magnetic properties of this compound and the resulting (H,T) phase diagram is discusse