Spin dynamics in the ${\mathrm{Nd}}_{2\mathrm{-}\mathit{x}}$${\mathrm{Ce}}_{\mathit{x}}$${\mathrm{CuO}}_4$ system: Estimation of the rate of spin fluctuations

We estimate the rate of fluctuations as ${10}^{11}$ ${\sec }^{\mathrm{-}1}$ in the normal state of ${\mathrm{Nd}}_{1.85}$${\mathrm{Ce}}_{0.15}$${\mathrm{CuO}}_4$ assuming that the spin fluctuations are the primary source of relaxation phenomena affecting the shape of the Mössbauer peaks. In the oxygenated and nonsuperconducting compound, the magnetic order is quasistatic rather than static as is generally believed. The spin clusters fluctuate at an approximate rate of ${10}^9$ ${\sec }^{\mathrm{-}1}$ below the Néel temperature. These findings may bear on the possible correlation between antiferromagnetic spin fluctuations and superconductivity. © 1996 The American Physical Society.