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

TL;DR

This study investigates ferromagnetic quantum critical fluctuations in YbRh2(Si0.95Ge0.05)2 through magnetic susceptibility measurements near the quantum critical point, revealing non-Fermi liquid behavior and enhanced magnetic ratios.

Contribution

It provides detailed experimental evidence of ferromagnetic quantum critical fluctuations and their scaling behavior in a heavy-fermion compound near its quantum critical point.

Findings

Susceptibility follows a T^{-0.6} dependence above 0.3 K.

Pauli susceptibility diverges as (B-B_c)^{-0.6} near the critical field.

The Sommerfeld-Wilson ratio reaches up to 30 close to the quantum critical point.

Abstract

The bulk magnetic susceptibility $\chi(T,B)$ 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: $\chi(T)\propto T^{-0.6}$ above 0.3 K, while at low temperatures the Pauli susceptibility follows $\chi_0\propto (B-B_c)^{-0.6}$ 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.