Evolution of ferromagnetic order in URhGe alloyed with Ru, Co and Si

Abstract

We have investigated the evolution of ferromagnetic order in the correlated metal URhGe (Curie temperature T C = 9.5 K) by chemical substitution of Ru, Co and Si. Polycrystalline samples URh 1−x Ru x Ge (x ≤ 0.6), URh 1−x Co x Ge (x ≤ 0.9) and URhGe 1−x Si x (x ≤ 0.2) have been prepared and the magnetic properties have been investigated by magnetization and transport experiments. In the case of Ru doping, T C initially increases, but then decreases linearly as a function of x and is completely suppressed for x cr ≈ 0.38. The Curie temperature in the URh 1−x Co x Ge series has a broad maximum T C = 20 K near x = 0.6 and then drops to 8 K for x = 0.9. In the case of Si doping T C stays roughly constant. We conclude that the alloy systems URh 1−x Ru x Ge and URh 1−x Co x Ge are interesting candidates to study the ferromagnetic instability.

Metallic quantum ferromagnets

“…This, together with the observation that URhGe is ferromagnetic, prompted the study of URh 1−x Co x Ge alloys (Sakarya et al, 2008), and the final conclusion was that UCoGe is indeed a weak ferromagnet with a Curie temperature near 3 K and a small ordered moment of 0.03 µ B (Huy et al, 2007b). The transition was found to be weakly first order by means of nuclear quadrupole resonance measurements (Hattori et al, 2010).…”

“…m Pressure decreases TC (Slooten et al, 2009); TCP not accessible. TC increases nonmonotonically upon doping with Rh (Sakarya et al, 2008); order of transition for URhxCo1−xGe not known except for x = 1 (2nd order with TC = 9.5 K). n Inferred from existence of tricritical wings.…”

Effect of Pressure on Magnetism of UIrGe

“…Isostructural compounds URhGe and UCoGe, which crystallize in a TiNiSi-type structure naturally fulfill this condition, and the coexistence of ferromagnetism (FM) and SC has been discovered here 8,9) . Both FM and SC can be affected by alloying [10][11][12][13][14] , the application of a magnetic field 15,16) , and the external pressure [17][18][19] . The resulting H-T-p-x phase diagrams corroborate the close connection between FM and SC.…”

Ferromagnetic order in U(Rh, Co)Ge

“…Previously, we reported the evolution of ferromagnetic order in URhGe upon replacing Rh by Ru or Co, or Ge by Si [14]. This work was motivated by the possibility to attain a ferromagnetic quantum critical point in URhGe by doping.…”

“…Notice, in the literature it was initially reported that UCoGe has a paramagnetic ground state [11,15]. Magnetization data taken on polycrystalline samples with x = 0.0, 0.2, 0.4, 0.6, 0.8 and 0.9 revealed that the Curie temperature (T C = 9.5 K for x = 0.0) increases up to T C = 20 K for x = 0.6, and then drops to 8.0 K for x = 0.9 [14]. These data hinted at a ferromagnetic instability for x d 1.0, but later experiments surprisingly showed ferromagnetism survives in the URh 1-x Co x Ge alloys up to x = 1.0 [2].…”