paper

Ferromagnetic quantum critical fluctuations in YbRh_2(Si_{0.95}Ge_{0.05})_2

arXiv:cond-mat/0501587 · doi:10.1103/PhysRevLett.94.076402

Abstract

The bulk magnetic susceptibility $I ¨ (T, B)$ of YbRh $_{2}$ (Si $_{0.95}$ Ge $_{0.05}$ ) $_{2}$ has been investigated %by ac-and dc-magnetometry at low temperatures and close to the field-induced quantum critical point at $B_{c} = 0.027$ T. For $B \leq 0.05$ T a Curie-Weiss law with a negative Weiss temperature is observed at temperatures below 0.3 K. Outside this region, the susceptibility indicates ferromagnetic quantum critical fluctuations: $I ¨ (T) \propto T^{- 0.6}$ above 0.3 K, while at low temperatures the Pauli susceptibility follows $I ¨ _{0} \propto (B - B_{c})^{- 0.6}$ and scales with the coefficient of the $T^{2}$ term in the electrical resistivity. The Sommerfeld-Wilson ratio is highly enhanced and increases up to 30 close to the critical field.

Physical Review Letters, to be published