Spin Disorder Scattering in Magnetic Metallic Alloys

Anomalous behavior of the resistivity at or just below the Néel temperature in antiferromagnetic metals is usually attributed to the formation of superzone gaps. However, we find that $R{\mathrm{M}\mathrm{n}}_{12-x}{\mathrm{F}\mathrm{e}}_x$ alloys which have no such gaps exhibit a similarly anomalous resistivity. We show that electron scattering by substitutional spin disorder can account for such behavior of itinerant magnets. This mechanism, which has not been studied before, leads to a relaxation rate that is proportional to $x(12-x)m^2$, where $m$ is the staggered magnetization. Together with spin fluctuations, phonon, and impurity scattering, it accounts well for the resistivity data we obtain for ${\mathrm{H}\mathrm{o}\mathrm{M}\mathrm{n}}_{12-x}{\mathrm{F}\mathrm{e}}_x$, for $0\le x\le 9$, in the temperature range of 4 to 400 K.