The Mössbauer spectra of the ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ nuclei in Au, ${\mathrm{Au}}^4$Mn, ${\mathrm{Au}}_3$Mn, ${\mathrm{Au}}_2$Mn, AuMn, Au${\mathrm{Mn}}_3$, and dilute alloys of Au in Mn have been measured at 4.2 °K. The isomer shift, magnetic dipole, and electric quadrupole splittings observed for these alloys are discussed in terms of the magnetic and crystalline structure. In these ordered gold-manganese alloys, the isomer shift as a function of composition departs widely from the linearity often observed for gold solid-solution alloys. For ${\mathrm{Au}}_2$Mn, we find an effective field at the ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ nucleus of 1590 kG as well as a large quadrupole coupling. The spectrum we observe for ${\mathrm{Au}}_2$Mn is consistent with the helical magnetic structure generally assumed for this alloy. A detailed analysis of this spectrum gives the magnetic moment ${\mu }^{*}=0.\mathrm{}415\pm 0.004 {\mu }_N$ for the 77.345-keV state of ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$, subject to a correction for the hyperfine-structure anomaly. For ${\mathrm{Au}}_2$Mn, Mössbauer measurements have also been made as a function of pressure between 0 and 46 kbars. A 7% increase in the magnitude of the effective field at the ${}_{}{}^{197}{}_{}{}^{}\mathrm{Au}$ nucleus is observed between 0 and 30 kbar. This may be due to the uncoiling of the Mn spin helix observed by other workers in this pressure range.

• Received 26 May 1969

DOI:https://doi.org/10.1103/PhysRevB.2.2440