The non-analytic momentum dependence of spin susceptibility of Heisenberg magnets in paramagnetic phase and its effect on critical exponents

Abstract

We study momentum dependence of static magnetic susceptibility $\chi (q)$ in paramagnetic phase of Heisenberg magnets and its relation to critical behavior within nonlinear sigma model (NLSM) at arbitrary dimension $2<d<4$. In the first order of $1/N$ expansion, where $N$ is the number of spin components, we find $\chi (q)\propto [q^2+{\xi }^{-2}(1+f(q\xi )){]}^{-1+\eta /2}$, where $\xi$ is the correlation length, $q$ is the momentum, measured from magnetic wave vector, the universal scaling function $f(x)$ describes deviation from the standard Landau-Ginzburg momentum dependence. In agreement with previous studies at large $x$ we find $f(x\gg 1)\simeq (2B_4/N)x^{4-d}$; the absolute value of the coefficient $B_4$ increases with $d$ at $d>5/2$. Using NLSM, we obtain the contribution of the"anomalous" term ${\xi }^{-2}f(q\xi )$ to the critical exponent $\nu$, comparing it to the contribution of the non-analytical dependence, originating from the critical exponent $\eta$ (the obtained critical exponents $\nu$ and $\eta$ agree with previous studies). In the range $3\le d<4$ we find that the former contribution dominates, and fully determines $1/N$ correction to the critical exponent $\nu$ in the limit $d\to 4.$

10 pages, 4 figures

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Cited by in corpus (1)

• Parametrizations of local vertex corrections from weak to strong coupling: importance of the Hedin three-leg vertex