The strongly enhanced magnetic excitations near the quantum critical point of Cr$_{1-x}$V$_x$ and why strong exchange enhancement need not imply heavy fermion behavior

TL;DR

This study uses inelastic neutron scattering to explore magnetic excitations in Cr-V alloys, revealing strong spin fluctuations near quantum criticality, and clarifies that large exchange enhancement does not necessarily lead to heavy fermion behavior.

Contribution

It demonstrates that significant exchange enhancement can occur without resulting in heavy fermion behavior, supported by neutron scattering data and a scaling relationship between heat capacity and spin relaxation.

Findings

Strong spin fluctuations up to 0.4 eV in Cr$_{0.95}$V$_{0.05}$

Exchange enhancement exceeds an order of magnitude

Scaling between heat capacity and spin relaxation rate

Abstract

Inelastic neutron scattering reveals strong spin fluctuations with energies as high as 0.4eV in the nearly antiferromagnetic metal Cr$_{0.95}$V$_{0.05}$. The magnetic response is well described by a modified Millis-Monien-Pines function. From the low-energy response, we deduce a large exchange enhancement, more than an order of magnitude larger than the corresponding enhancement of the low-temperature electronic heat capacity $\gamma T$. A scaling relationship between $\gamma$ and the inverse of the wavevector- averaged spin relaxation rate $\Gamma_{\text{ave}}$ is demonstrated for a number of magnetically correlated metals