Resistivity of Nearly Antiferromagnetic Metals

Abstract

The effect of spin fluctuations in nearly ferromagnetic metals (nfm) on such properties as resistivity and electronic specific heat has been discussed recently by several authors.1,2 In these systems, which are close to satisfying Stoner’s criterion for ferromagnetism, large-amplitude, low-frequency spin fluctuations occur for small wave vectors q. Although heavily damped, these electron—hole collective excitations renormalize the electron mass, which can become large, inducing important changes in the electronic specific heat. Another effect, in transition metals like Pd, for instance, is conduction electron scattering, induced by the s—d exchange coupling, which connects the spin fluctuations within the nearly ferromagnetic d band and the s-like conduction states. As discussed in detail previously,3 ferromagnetic spin fluctuations introduce a term proportional to χ1/2 T 2 in the resistivity, where χ is the static d-spin susceptibility, which diverges at the ferromagnetic instability. Recently the effect of spin fluctuations in nearly antiferromagnetic metals (nam) on the electronic specific heat was discussed by several authors.4,5 In these systems the real part Reχ(q,ω) of the dynamic susceptibility exhibits a maximum for low frequencies around a finite wave vector Q ≠ 0. The Stoner criterion U Re χ(q, 0) = 1 then predicts spin fluctuations of wave vector Q + q, q being small. The width ∆q of the spin fluctuation spectrum depends on the details of the band structure. The antiferromagnetic spin fluctuations occur around a finite wave vector, and are not isotropic in reciprocal space, i.e., Im χ(q,ω) depends not only on the magnitude of q, but on its direction. This introduces new features in the scattering properties.