Strongly enhanced magnetic excitations near the quantum critical point of Cr1-xVx and why strong exchange enhancement need not imply heavy fermion behavior

Inelastic neutron scattering reveals strong spin fluctuations with energies as high as 0.4 eV in the nearly antiferromagnetic metal Cr0.95V0.05. 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 wave vector-averaged spin relaxation rate Gamma(ave) is demonstrated for a number of magnetically correlated metals.